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Message-ID: <20240402150851.UCzI_vtV@linutronix.de>
Date: Tue, 2 Apr 2024 17:08:51 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, linux-rt-users@...r.kernel.org,
Steven Rostedt <rostedt@...dmis.org>
Subject: [ANNOUNCE] v6.8.2-rt10
Dear RT folks!
I'm pleased to announce the v6.8.2-rt10 patch set.
Changes since v6.8.2-rt9:
- Update of the printk series by John Ogness:
- remove return value for write_thread()/write_atomic() nbcon callbacks
(use struct nbcon_write_context @outbuf to determine if ownership was
lost while in a nbcon printing callback).
- rename driver_enter()/driver_exit() nbcon callbacks to
device_lock()/device_unlock().
- add a WARN_ON_ONCE if 8250 console is running in rs485 mode.
- introduce a new struct nbcon_drvdata to track nbcon ownership for
non-printing activities (and remove the @nbcon_locked_port flag that
was used for this purpose in a racy way).
- synchronize setting of struct uart_port @cons to avoid possible races
when handling uart ports that may be in the process of registering or
unregistering.
- print a message "** replaying previous printk message **" if a console
printer is interrupted by a higher priority printer and the
interrupted message is reprinted.
- mark all lockdep splats as emergency sections.
- mark all rcu stall splats as emergency sections.
- fixup nbcon sequence number initialization.
- for atomic flushing, flush an nbcon completely before flushing the
next console (and maintain console ownership throughout the atomic
flushing).
- when exiting the emergency state, flush the nbcon atomic consoles
directly.
- during panic, try to flush the legacy consoles directly rather than
relying on irq_work.
- for nbcon atomic consoles, lock the device when transitioning to
registered status.
- add a compiler barrier to pr_flush() to ensure the compiler does not
optimize variable usage in a racy way.
Known issues
None.
The delta patch against v6.8.2-rt9 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.8/incr/patch-6.8.2-rt9-rt10.patch.xz
You can get this release via the git tree at:
https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v6.8.2-rt10
The RT patch against v6.8.2 can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patch-6.8.2-rt10.patch.xz
The split quilt queue is available at:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt10.tar.xz
Sebastian
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index ae637155fe7cd..4e4f5501d81da 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -601,35 +601,37 @@ static void univ8250_console_write(struct console *co, const char *s,
serial8250_console_write(up, s, count);
}
#else
-static bool univ8250_console_write_atomic(struct console *co,
+static void univ8250_console_write_atomic(struct console *co,
struct nbcon_write_context *wctxt)
{
struct uart_8250_port *up = &serial8250_ports[co->index];
- return serial8250_console_write_atomic(up, wctxt);
+ serial8250_console_write_atomic(up, wctxt);
}
-static bool univ8250_console_write_thread(struct console *co,
+static void univ8250_console_write_thread(struct console *co,
struct nbcon_write_context *wctxt)
{
struct uart_8250_port *up = &serial8250_ports[co->index];
- return serial8250_console_write_thread(up, wctxt);
+ serial8250_console_write_thread(up, wctxt);
}
-static void univ8250_console_driver_enter(struct console *con, unsigned long *flags)
+static void univ8250_console_device_lock(struct console *con, unsigned long *flags)
{
struct uart_port *up = &serial8250_ports[con->index].port;
__uart_port_lock_irqsave(up, flags);
}
-static void univ8250_console_driver_exit(struct console *con, unsigned long flags)
+static void univ8250_console_device_unlock(struct console *con, unsigned long flags)
{
struct uart_port *up = &serial8250_ports[con->index].port;
__uart_port_unlock_irqrestore(up, flags);
}
+
+static struct nbcon_drvdata serial8250_nbcon_drvdata;
#endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */
static int univ8250_console_setup(struct console *co, char *options)
@@ -659,11 +661,11 @@ static int univ8250_console_setup(struct console *co, char *options)
port = &serial8250_ports[co->index].port;
/* link port to console */
- port->cons = co;
+ uart_port_set_cons(port, co);
retval = serial8250_console_setup(port, options, false);
if (retval != 0)
- port->cons = NULL;
+ uart_port_set_cons(port, NULL);
return retval;
}
@@ -721,7 +723,7 @@ static int univ8250_console_match(struct console *co, char *name, int idx,
continue;
co->index = i;
- port->cons = co;
+ uart_port_set_cons(port, co);
return serial8250_console_setup(port, options, true);
}
@@ -736,9 +738,10 @@ static struct console univ8250_console = {
#else
.write_atomic = univ8250_console_write_atomic,
.write_thread = univ8250_console_write_thread,
- .driver_enter = univ8250_console_driver_enter,
- .driver_exit = univ8250_console_driver_exit,
+ .device_lock = univ8250_console_device_lock,
+ .device_unlock = univ8250_console_device_unlock,
.flags = CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON,
+ .nbcon_drvdata = &serial8250_nbcon_drvdata,
#endif
.device = uart_console_device,
.setup = univ8250_console_setup,
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index f799c34f1603c..ed50b434d8c80 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -551,8 +551,10 @@ static int serial8250_em485_init(struct uart_8250_port *p)
return -ENOMEM;
#ifndef CONFIG_SERIAL_8250_LEGACY_CONSOLE
- if (uart_console(&p->port))
+ if (uart_console(&p->port)) {
dev_warn(p->port.dev, "no atomic printing for rs485 consoles\n");
+ p->port.cons->write_atomic = NULL;
+ }
#endif
hrtimer_init(&p->em485->stop_tx_timer, CLOCK_MONOTONIC,
@@ -3293,7 +3295,6 @@ void serial8250_init_port(struct uart_8250_port *up)
struct uart_port *port = &up->port;
spin_lock_init(&port->lock);
- port->nbcon_locked_port = false;
port->ctrl_id = 0;
port->pm = NULL;
port->ops = &serial8250_pops;
@@ -3497,18 +3498,17 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s,
uart_port_unlock_irqrestore(port, flags);
}
#else
-bool serial8250_console_write_thread(struct uart_8250_port *up,
+void serial8250_console_write_thread(struct uart_8250_port *up,
struct nbcon_write_context *wctxt)
{
struct uart_8250_em485 *em485 = up->em485;
struct uart_port *port = &up->port;
- bool done = false;
unsigned int ier;
touch_nmi_watchdog();
if (!nbcon_enter_unsafe(wctxt))
- return false;
+ return;
/* First save IER then disable the interrupts. */
ier = serial_port_in(port, UART_IER);
@@ -3554,7 +3554,6 @@ bool serial8250_console_write_thread(struct uart_8250_port *up,
break;
}
}
- done = (i == len);
} else {
nbcon_reacquire(wctxt);
}
@@ -3580,24 +3579,23 @@ bool serial8250_console_write_thread(struct uart_8250_port *up,
if (up->msr_saved_flags)
serial8250_modem_status(up);
- /* Success if no handover/takeover and message fully printed. */
- return (nbcon_exit_unsafe(wctxt) && done);
+ nbcon_exit_unsafe(wctxt);
}
-bool serial8250_console_write_atomic(struct uart_8250_port *up,
+void serial8250_console_write_atomic(struct uart_8250_port *up,
struct nbcon_write_context *wctxt)
{
struct uart_port *port = &up->port;
unsigned int ier;
/* Atomic console not supported for rs485 mode. */
- if (up->em485)
- return false;
+ if (WARN_ON_ONCE(up->em485))
+ return;
touch_nmi_watchdog();
if (!nbcon_enter_unsafe(wctxt))
- return false;
+ return;
/*
* First save IER then disable the interrupts. The special variant to
@@ -3621,8 +3619,7 @@ bool serial8250_console_write_atomic(struct uart_8250_port *up,
wait_for_xmitr(up, UART_LSR_BOTH_EMPTY);
serial_port_out(port, UART_IER, ier);
- /* Success if no handover/takeover. */
- return nbcon_exit_unsafe(wctxt);
+ nbcon_exit_unsafe(wctxt);
}
#endif /* CONFIG_SERIAL_8250_LEGACY_CONSOLE */
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 2fa3fb30dc6c7..7618a5783adbc 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2488,7 +2488,7 @@ static int pl011_console_match(struct console *co, char *name, int idx,
continue;
co->index = i;
- port->cons = co;
+ uart_port_set_cons(port, co);
return pl011_console_setup(co, options);
}
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index d6a58a9e072a1..2652b4d5c944d 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -3146,7 +3146,7 @@ static int serial_core_add_one_port(struct uart_driver *drv, struct uart_port *u
uport->state = state;
state->pm_state = UART_PM_STATE_UNDEFINED;
- uport->cons = drv->cons;
+ uart_port_set_cons(uport, drv->cons);
uport->minor = drv->tty_driver->minor_start + uport->line;
uport->name = kasprintf(GFP_KERNEL, "%s%d", drv->dev_name,
drv->tty_driver->name_base + uport->line);
diff --git a/include/linux/console.h b/include/linux/console.h
index 02d6cabbe5009..0b6c122918174 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -284,6 +284,25 @@ struct nbcon_write_context {
bool unsafe_takeover;
};
+/**
+ * struct nbcon_drvdata - Data to allow nbcon acquire in non-print context
+ * @ctxt: The core console context
+ * @srcu_cookie: Storage for a console_srcu_lock cookie, if needed
+ * @owner_index: Storage for the owning console index, if needed
+ * @locked: Storage for the locked state, if needed
+ *
+ * All fields (except for @ctxt) are available exclusively to the driver to
+ * use as needed. They are not used by the printk subsystem.
+ */
+struct nbcon_drvdata {
+ struct nbcon_context __private ctxt;
+
+ /* reserved for driver use */
+ int srcu_cookie;
+ short owner_index;
+ bool locked;
+};
+
/**
* struct console - The console descriptor structure
* @name: The name of the console driver
@@ -306,6 +325,7 @@ struct nbcon_write_context {
*
* @nbcon_state: State for nbcon consoles
* @nbcon_seq: Sequence number of the next record for nbcon to print
+ * @nbcon_prev_seq: Seq num the previous nbcon owner was assigned to print
* @pbufs: Pointer to nbcon private buffer
* @kthread: Printer kthread for this console
* @rcuwait: RCU-safe wait object for @kthread waking
@@ -335,7 +355,7 @@ struct console {
/**
* @write_atomic:
*
- * NBCON callback to write out text in any context. (Optional)
+ * NBCON callback to write out text in any context.
*
* This callback is called with the console already acquired. The
* callback can use nbcon_can_proceed() at any time to verify that
@@ -359,11 +379,8 @@ struct console {
* This callback can be called from any context (including NMI).
* Therefore it must avoid usage of any locking and instead rely
* on the console ownership for synchronization.
- *
- * Returns true if all text was successfully written out and
- * ownership was never lost, otherwise false.
*/
- bool (*write_atomic)(struct console *con, struct nbcon_write_context *wctxt);
+ void (*write_atomic)(struct console *con, struct nbcon_write_context *wctxt);
/**
* @write_thread:
@@ -372,7 +389,7 @@ struct console {
*
* This callback is called with the console already acquired. Any
* additional driver synchronization should have been performed by
- * driver_enter().
+ * device_lock().
*
* This callback is always called from task context but with migration
* disabled.
@@ -383,60 +400,70 @@ struct console {
* during normal operation and is always called from task context.
* This provides drivers with a relatively relaxed locking context
* for synchronizing output to the hardware.
- *
- * Returns true if all text was successfully written out, otherwise
- * false.
*/
- bool (*write_thread)(struct console *con, struct nbcon_write_context *wctxt);
+ void (*write_thread)(struct console *con, struct nbcon_write_context *wctxt);
/**
- * @driver_enter:
+ * @device_lock:
*
* NBCON callback to begin synchronization with driver code.
- * (Required for NBCON if write_thread is provided)
*
* Console drivers typically must deal with access to the hardware
* via user input/output (such as an interactive login shell) and
* output of kernel messages via printk() calls. This callback is
- * called before the kernel begins output via the write_thread()
- * callback due to printk() calls. The driver can use this
- * callback to acquire some driver lock in order to synchronize
- * against user input/output (or any other driver functionality).
+ * called by the printk-subsystem whenever it needs to synchronize
+ * with hardware access by the driver. It should be implemented to
+ * use whatever synchronization mechanism the driver is using for
+ * itself (for example, the port lock for uart serial consoles).
*
* This callback is always called from task context. It may use any
* synchronization method required by the driver. BUT this callback
- * MUST disable migration. The console driver may be using a
- * sychronization mechanism that already takes care of this (such as
+ * MUST also disable migration. The console driver may be using a
+ * synchronization mechanism that already takes care of this (such as
* spinlocks). Otherwise this function must explicitly call
* migrate_disable().
*
* The flags argument is provided as a convenience to the driver. It
- * will be passed again to driver_exit() when printing is completed
+ * will be passed again to device_unlock() when printing is completed
* (for example, if spin_lock_irqsave() was used). It can be ignored
* if the driver does not need it.
*/
- void (*driver_enter)(struct console *con, unsigned long *flags);
+ void (*device_lock)(struct console *con, unsigned long *flags);
/**
- * @driver_exit:
+ * @device_unlock:
*
* NBCON callback to finish synchronization with driver code.
- * (Required for NBCON if write_thread is provided)
*
- * This callback is called after the kernel has finished printing a
- * printk message. It is the counterpart to driver_enter().
+ * It is the counterpart to device_lock().
*
* This callback is always called from task context. It must
- * appropriately re-enable migration (depending on how driver_enter()
+ * appropriately re-enable migration (depending on how device_lock()
* disabled migration).
*
* The flags argument is the value of the same variable that was
- * passed to driver_enter().
+ * passed to device_lock().
*/
- void (*driver_exit)(struct console *con, unsigned long flags);
+ void (*device_unlock)(struct console *con, unsigned long flags);
atomic_t __private nbcon_state;
atomic_long_t __private nbcon_seq;
+ atomic_long_t __private nbcon_prev_seq;
+
+ /**
+ * @nbcon_drvdata:
+ *
+ * Data for nbcon ownership tracking to allow acquiring nbcon consoles
+ * in non-printing contexts.
+ *
+ * Drivers may need to acquire nbcon consoles in non-printing
+ * contexts. This is achieved by providing a struct nbcon_drvdata.
+ * Then the driver can call nbcon_driver_acquire() and
+ * nbcon_driver_release(). The struct does not require any special
+ * initialization.
+ */
+ struct nbcon_drvdata *nbcon_drvdata;
+
struct printk_buffers *pbufs;
struct task_struct *kthread;
struct rcuwait rcuwait;
@@ -469,28 +496,29 @@ extern void console_list_unlock(void) __releases(console_mutex);
extern struct hlist_head console_list;
/**
- * console_srcu_read_flags - Locklessly read the console flags
+ * console_srcu_read_flags - Locklessly read flags of a possibly registered
+ * console
* @con: struct console pointer of console to read flags from
*
- * This function provides the necessary READ_ONCE() and data_race()
- * notation for locklessly reading the console flags. The READ_ONCE()
- * in this function matches the WRITE_ONCE() when @flags are modified
- * for registered consoles with console_srcu_write_flags().
+ * Locklessly reading @con->flags provides a consistent read value because
+ * there is at most one CPU modifying @con->flags and that CPU is using only
+ * read-modify-write operations to do so.
*
- * Only use this function to read console flags when locklessly
- * iterating the console list via srcu.
+ * Requires console_srcu_read_lock to be held, which implies that @con might
+ * be a registered console. If the caller is holding the console_list_lock or
+ * it is certain that the console is not registered, the caller may read
+ * @con->flags directly instead.
*
* Context: Any context.
+ * Return: The current value of the @con->flags field.
*/
static inline short console_srcu_read_flags(const struct console *con)
{
WARN_ON_ONCE(!console_srcu_read_lock_is_held());
/*
- * Locklessly reading console->flags provides a consistent
- * read value because there is at most one CPU modifying
- * console->flags and that CPU is using only read-modify-write
- * operations to do so.
+ * The READ_ONCE() matches the WRITE_ONCE() when @flags are modified
+ * for registered consoles with console_srcu_write_flags().
*/
return data_race(READ_ONCE(con->flags));
}
diff --git a/include/linux/printk.h b/include/linux/printk.h
index a2d40a6372266..f2074b458d801 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -9,7 +9,7 @@
#include <linux/ratelimit_types.h>
#include <linux/once_lite.h>
-struct uart_port;
+struct console;
extern const char linux_banner[];
extern const char linux_proc_banner[];
@@ -159,8 +159,6 @@ int _printk(const char *fmt, ...);
*/
__printf(1, 2) __cold int _printk_deferred(const char *fmt, ...);
-extern void __printk_safe_enter(void);
-extern void __printk_safe_exit(void);
extern void __printk_deferred_enter(void);
extern void __printk_deferred_exit(void);
@@ -198,8 +196,8 @@ extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
extern asmlinkage void dump_stack(void) __cold;
void printk_trigger_flush(void);
void printk_legacy_allow_panic_sync(void);
-extern void uart_nbcon_acquire(struct uart_port *up);
-extern void uart_nbcon_release(struct uart_port *up);
+extern void nbcon_driver_acquire(struct console *con);
+extern void nbcon_driver_release(struct console *con);
void nbcon_atomic_flush_unsafe(void);
#else
static inline __printf(1, 0)
@@ -285,11 +283,11 @@ static inline void printk_legacy_allow_panic_sync(void)
{
}
-static inline void uart_nbcon_acquire(struct uart_port *up)
+static inline void nbcon_driver_acquire(struct console *con)
{
}
-static inline void uart_nbcon_release(struct uart_port *up)
+static inline void nbcon_driver_release(struct console *con)
{
}
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index ec46e3b49ee99..ff445a5fca281 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -206,9 +206,9 @@ void serial8250_init_port(struct uart_8250_port *up);
void serial8250_set_defaults(struct uart_8250_port *up);
void serial8250_console_write(struct uart_8250_port *up, const char *s,
unsigned int count);
-bool serial8250_console_write_atomic(struct uart_8250_port *up,
+void serial8250_console_write_atomic(struct uart_8250_port *up,
struct nbcon_write_context *wctxt);
-bool serial8250_console_write_thread(struct uart_8250_port *up,
+void serial8250_console_write_thread(struct uart_8250_port *up,
struct nbcon_write_context *wctxt);
int serial8250_console_setup(struct uart_port *port, char *options, bool probe);
int serial8250_console_exit(struct uart_port *port);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index b003e658bb39e..9a73dee32ad9a 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -8,10 +8,13 @@
#define LINUX_SERIAL_CORE_H
#include <linux/bitops.h>
+#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/console.h>
#include <linux/interrupt.h>
#include <linux/circ_buf.h>
+#include <linux/lockdep.h>
+#include <linux/printk.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/tty.h>
@@ -488,7 +491,6 @@ struct uart_port {
struct uart_icount icount; /* statistics */
struct console *cons; /* struct console, if any */
- bool nbcon_locked_port; /* True, if the port is locked by nbcon */
/* flags must be updated while holding port mutex */
upf_t flags;
@@ -589,6 +591,101 @@ struct uart_port {
void *private_data; /* generic platform data pointer */
};
+/*
+ * Only for console->device_lock()/_unlock() callbacks and internal
+ * port lock wrapper synchronization.
+ */
+static inline void __uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
+{
+ spin_lock_irqsave(&up->lock, *flags);
+}
+
+/*
+ * Only for console->device_lock()/_unlock() callbacks and internal
+ * port lock wrapper synchronization.
+ */
+static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
+{
+ spin_unlock_irqrestore(&up->lock, flags);
+}
+
+/**
+ * uart_port_set_cons - Safely set the @cons field for a uart
+ * @up: The uart port to set
+ * @con: The new console to set to
+ *
+ * This function must be used to set @up->cons. It uses the port lock to
+ * synchronize with the port lock wrappers in order to ensure that the console
+ * cannot change or disappear while another context is holding the port lock.
+ */
+static inline void uart_port_set_cons(struct uart_port *up, struct console *con)
+{
+ unsigned long flags;
+
+ __uart_port_lock_irqsave(up, &flags);
+ up->cons = con;
+ __uart_port_unlock_irqrestore(up, flags);
+}
+
+/* Only for internal port lock wrapper usage. */
+static inline void __uart_port_nbcon_acquire(struct uart_port *up)
+{
+ lockdep_assert_held_once(&up->lock);
+
+ if (likely(!uart_console(up)))
+ return;
+
+ if (up->cons->nbcon_drvdata) {
+ /*
+ * If @up->cons is registered, prevent it from fully
+ * unregistering until this context releases the nbcon.
+ */
+ int cookie = console_srcu_read_lock();
+
+ /* Ensure console is registered and is an nbcon console. */
+ if (!hlist_unhashed_lockless(&up->cons->node) &&
+ (console_srcu_read_flags(up->cons) & CON_NBCON)) {
+ WARN_ON_ONCE(up->cons->nbcon_drvdata->locked);
+
+ nbcon_driver_acquire(up->cons);
+
+ /*
+ * Record @up->line to be used during release because
+ * @up->cons->index can change while the port and
+ * nbcon are locked.
+ */
+ up->cons->nbcon_drvdata->owner_index = up->line;
+ up->cons->nbcon_drvdata->srcu_cookie = cookie;
+ up->cons->nbcon_drvdata->locked = true;
+ } else {
+ console_srcu_read_unlock(cookie);
+ }
+ }
+}
+
+/* Only for internal port lock wrapper usage. */
+static inline void __uart_port_nbcon_release(struct uart_port *up)
+{
+ lockdep_assert_held_once(&up->lock);
+
+ /*
+ * uart_console() cannot be used here because @up->cons->index might
+ * have changed. Check against @up->cons->nbcon_drvdata->owner_index
+ * instead.
+ */
+
+ if (unlikely(up->cons &&
+ up->cons->nbcon_drvdata &&
+ up->cons->nbcon_drvdata->locked &&
+ up->cons->nbcon_drvdata->owner_index == up->line)) {
+ WARN_ON_ONCE(!up->cons->nbcon_drvdata->locked);
+
+ up->cons->nbcon_drvdata->locked = false;
+ nbcon_driver_release(up->cons);
+ console_srcu_read_unlock(up->cons->nbcon_drvdata->srcu_cookie);
+ }
+}
+
/**
* uart_port_lock - Lock the UART port
* @up: Pointer to UART port structure
@@ -596,7 +693,7 @@ struct uart_port {
static inline void uart_port_lock(struct uart_port *up)
{
spin_lock(&up->lock);
- uart_nbcon_acquire(up);
+ __uart_port_nbcon_acquire(up);
}
/**
@@ -606,7 +703,7 @@ static inline void uart_port_lock(struct uart_port *up)
static inline void uart_port_lock_irq(struct uart_port *up)
{
spin_lock_irq(&up->lock);
- uart_nbcon_acquire(up);
+ __uart_port_nbcon_acquire(up);
}
/**
@@ -617,7 +714,7 @@ static inline void uart_port_lock_irq(struct uart_port *up)
static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
{
spin_lock_irqsave(&up->lock, *flags);
- uart_nbcon_acquire(up);
+ __uart_port_nbcon_acquire(up);
}
/**
@@ -631,7 +728,7 @@ static inline bool uart_port_trylock(struct uart_port *up)
if (!spin_trylock(&up->lock))
return false;
- uart_nbcon_acquire(up);
+ __uart_port_nbcon_acquire(up);
return true;
}
@@ -647,7 +744,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long
if (!spin_trylock_irqsave(&up->lock, *flags))
return false;
- uart_nbcon_acquire(up);
+ __uart_port_nbcon_acquire(up);
return true;
}
@@ -657,7 +754,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long
*/
static inline void uart_port_unlock(struct uart_port *up)
{
- uart_nbcon_release(up);
+ __uart_port_nbcon_release(up);
spin_unlock(&up->lock);
}
@@ -667,7 +764,7 @@ static inline void uart_port_unlock(struct uart_port *up)
*/
static inline void uart_port_unlock_irq(struct uart_port *up)
{
- uart_nbcon_release(up);
+ __uart_port_nbcon_release(up);
spin_unlock_irq(&up->lock);
}
@@ -678,19 +775,7 @@ static inline void uart_port_unlock_irq(struct uart_port *up)
*/
static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
{
- uart_nbcon_release(up);
- spin_unlock_irqrestore(&up->lock, flags);
-}
-
-/* Only for use in the console->driver_enter() callback. */
-static inline void __uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags)
-{
- spin_lock_irqsave(&up->lock, *flags);
-}
-
-/* Only for use in the console->driver_exit() callback. */
-static inline void __uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags)
-{
+ __uart_port_nbcon_release(up);
spin_unlock_irqrestore(&up->lock, flags);
}
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 5c21ba41e3087..80cfbe7b340e3 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -575,8 +575,10 @@ static struct lock_trace *save_trace(void)
if (!debug_locks_off_graph_unlock())
return NULL;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return NULL;
}
@@ -783,6 +785,8 @@ static void lockdep_print_held_locks(struct task_struct *p)
{
int i, depth = READ_ONCE(p->lockdep_depth);
+ nbcon_cpu_emergency_enter();
+
if (!depth)
printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
else
@@ -793,11 +797,13 @@ static void lockdep_print_held_locks(struct task_struct *p)
* and it's not the current task.
*/
if (p != current && task_is_running(p))
- return;
+ goto out;
for (i = 0; i < depth; i++) {
printk(" #%d: ", i);
print_lock(p->held_locks + i);
}
+out:
+ nbcon_cpu_emergency_exit();
}
static void print_kernel_ident(void)
@@ -889,11 +895,13 @@ look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
instrumentation_begin();
debug_locks_off();
+ nbcon_cpu_emergency_enter();
printk(KERN_ERR
"BUG: looking up invalid subclass: %u\n", subclass);
printk(KERN_ERR
"turning off the locking correctness validator.\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
instrumentation_end();
return NULL;
}
@@ -970,11 +978,13 @@ static bool assign_lock_key(struct lockdep_map *lock)
else {
/* Debug-check: all keys must be persistent! */
debug_locks_off();
+ nbcon_cpu_emergency_enter();
pr_err("INFO: trying to register non-static key.\n");
pr_err("The code is fine but needs lockdep annotation, or maybe\n");
pr_err("you didn't initialize this object before use?\n");
pr_err("turning off the locking correctness validator.\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
return false;
}
@@ -1318,8 +1328,10 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
return NULL;
}
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return NULL;
}
nr_lock_classes++;
@@ -1351,11 +1363,13 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
if (verbose(class)) {
graph_unlock();
+ nbcon_cpu_emergency_enter();
printk("\nnew class %px: %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
if (!graph_lock()) {
return NULL;
@@ -1394,8 +1408,10 @@ static struct lock_list *alloc_list_entry(void)
if (!debug_locks_off_graph_unlock())
return NULL;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return NULL;
}
nr_list_entries++;
@@ -2041,6 +2057,8 @@ static noinline void print_circular_bug(struct lock_list *this,
depth = get_lock_depth(target);
+ nbcon_cpu_emergency_enter();
+
print_circular_bug_header(target, depth, check_src, check_tgt);
parent = get_lock_parent(target);
@@ -2059,6 +2077,8 @@ static noinline void print_circular_bug(struct lock_list *this,
printk("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static noinline void print_bfs_bug(int ret)
@@ -2571,6 +2591,8 @@ print_bad_irq_dependency(struct task_struct *curr,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=====================================================\n");
pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
@@ -2620,11 +2642,13 @@ print_bad_irq_dependency(struct task_struct *curr,
pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
next_root->trace = save_trace();
if (!next_root->trace)
- return;
+ goto out;
print_shortest_lock_dependencies(forwards_entry, next_root);
pr_warn("\nstack backtrace:\n");
dump_stack();
+out:
+ nbcon_cpu_emergency_exit();
}
static const char *state_names[] = {
@@ -2989,6 +3013,8 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("============================================\n");
pr_warn("WARNING: possible recursive locking detected\n");
@@ -3011,6 +3037,8 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
/*
@@ -3608,6 +3636,8 @@ static void print_collision(struct task_struct *curr,
struct held_lock *hlock_next,
struct lock_chain *chain)
{
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("============================\n");
pr_warn("WARNING: chain_key collision\n");
@@ -3624,6 +3654,8 @@ static void print_collision(struct task_struct *curr,
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
#endif
@@ -3714,8 +3746,10 @@ static inline int add_chain_cache(struct task_struct *curr,
if (!debug_locks_off_graph_unlock())
return 0;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return 0;
}
chain->chain_key = chain_key;
@@ -3732,8 +3766,10 @@ static inline int add_chain_cache(struct task_struct *curr,
if (!debug_locks_off_graph_unlock())
return 0;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return 0;
}
@@ -4038,6 +4074,8 @@ print_irq_inversion_bug(struct task_struct *curr,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("========================================================\n");
pr_warn("WARNING: possible irq lock inversion dependency detected\n");
@@ -4078,11 +4116,13 @@ print_irq_inversion_bug(struct task_struct *curr,
pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
root->trace = save_trace();
if (!root->trace)
- return;
+ goto out;
print_shortest_lock_dependencies(other, root);
pr_warn("\nstack backtrace:\n");
dump_stack();
+out:
+ nbcon_cpu_emergency_exit();
}
/*
@@ -4159,6 +4199,8 @@ void print_irqtrace_events(struct task_struct *curr)
{
const struct irqtrace_events *trace = &curr->irqtrace;
+ nbcon_cpu_emergency_enter();
+
printk("irq event stamp: %u\n", trace->irq_events);
printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
@@ -4172,6 +4214,8 @@ void print_irqtrace_events(struct task_struct *curr)
printk("softirqs last disabled at (%u): [<%px>] %pS\n",
trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
(void *)trace->softirq_disable_ip);
+
+ nbcon_cpu_emergency_exit();
}
static int HARDIRQ_verbose(struct lock_class *class)
@@ -4692,10 +4736,12 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
* We must printk outside of the graph_lock:
*/
if (ret == 2) {
+ nbcon_cpu_emergency_enter();
printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
print_lock(this);
print_irqtrace_events(curr);
dump_stack();
+ nbcon_cpu_emergency_exit();
}
return ret;
@@ -4736,6 +4782,8 @@ print_lock_invalid_wait_context(struct task_struct *curr,
if (debug_locks_silent)
return 0;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=============================\n");
pr_warn("[ BUG: Invalid wait context ]\n");
@@ -4755,6 +4803,8 @@ print_lock_invalid_wait_context(struct task_struct *curr,
pr_warn("stack backtrace:\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
+
return 0;
}
@@ -4959,6 +5009,8 @@ print_lock_nested_lock_not_held(struct task_struct *curr,
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("==================================\n");
pr_warn("WARNING: Nested lock was not taken\n");
@@ -4979,6 +5031,8 @@ print_lock_nested_lock_not_held(struct task_struct *curr,
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static int __lock_is_held(const struct lockdep_map *lock, int read);
@@ -5024,11 +5078,13 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
debug_class_ops_inc(class);
if (very_verbose(class)) {
+ nbcon_cpu_emergency_enter();
printk("\nacquire class [%px] %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
}
/*
@@ -5155,6 +5211,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
#endif
if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
debug_locks_off();
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
printk(KERN_DEBUG "depth: %i max: %lu!\n",
curr->lockdep_depth, MAX_LOCK_DEPTH);
@@ -5162,6 +5219,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
lockdep_print_held_locks(current);
debug_show_all_locks();
dump_stack();
+ nbcon_cpu_emergency_exit();
return 0;
}
@@ -5181,6 +5239,8 @@ static void print_unlock_imbalance_bug(struct task_struct *curr,
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=====================================\n");
pr_warn("WARNING: bad unlock balance detected!\n");
@@ -5197,6 +5257,8 @@ static void print_unlock_imbalance_bug(struct task_struct *curr,
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static noinstr int match_held_lock(const struct held_lock *hlock,
@@ -5900,6 +5962,8 @@ static void print_lock_contention_bug(struct task_struct *curr,
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=================================\n");
pr_warn("WARNING: bad contention detected!\n");
@@ -5916,6 +5980,8 @@ static void print_lock_contention_bug(struct task_struct *curr,
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static void
@@ -6529,6 +6595,8 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=========================\n");
pr_warn("WARNING: held lock freed!\n");
@@ -6541,6 +6609,8 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static inline int not_in_range(const void* mem_from, unsigned long mem_len,
@@ -6587,6 +6657,8 @@ static void print_held_locks_bug(void)
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("====================================\n");
pr_warn("WARNING: %s/%d still has locks held!\n",
@@ -6596,6 +6668,8 @@ static void print_held_locks_bug(void)
lockdep_print_held_locks(current);
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
void debug_check_no_locks_held(void)
@@ -6614,6 +6688,7 @@ void debug_show_all_locks(void)
pr_warn("INFO: lockdep is turned off.\n");
return;
}
+ nbcon_cpu_emergency_enter();
pr_warn("\nShowing all locks held in the system:\n");
rcu_read_lock();
@@ -6628,6 +6703,7 @@ void debug_show_all_locks(void)
pr_warn("\n");
pr_warn("=============================================\n\n");
+ nbcon_cpu_emergency_exit();
}
EXPORT_SYMBOL_GPL(debug_show_all_locks);
#endif
@@ -6653,6 +6729,7 @@ asmlinkage __visible void lockdep_sys_exit(void)
if (unlikely(curr->lockdep_depth)) {
if (!debug_locks_off())
return;
+ nbcon_cpu_emergency_enter();
pr_warn("\n");
pr_warn("================================================\n");
pr_warn("WARNING: lock held when returning to user space!\n");
@@ -6661,6 +6738,7 @@ asmlinkage __visible void lockdep_sys_exit(void)
pr_warn("%s/%d is leaving the kernel with locks still held!\n",
curr->comm, curr->pid);
lockdep_print_held_locks(curr);
+ nbcon_cpu_emergency_exit();
}
/*
@@ -6677,6 +6755,7 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
bool rcu = warn_rcu_enter();
/* Note: the following can be executed concurrently, so be careful. */
+ nbcon_cpu_emergency_enter();
pr_warn("\n");
pr_warn("=============================\n");
pr_warn("WARNING: suspicious RCU usage\n");
@@ -6715,6 +6794,7 @@ void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
warn_rcu_exit(rcu);
}
EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
diff --git a/kernel/panic.c b/kernel/panic.c
index 9fa44bc38f466..3754a2471b4ff 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -364,14 +364,14 @@ void panic(const char *fmt, ...)
panic_other_cpus_shutdown(_crash_kexec_post_notifiers);
+ printk_legacy_allow_panic_sync();
+
/*
* Run any panic handlers, including those that might need to
* add information to the kmsg dump output.
*/
atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
- printk_legacy_allow_panic_sync();
-
panic_print_sys_info(false);
kmsg_dump(KMSG_DUMP_PANIC);
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 1abb4207186f0..fdf455c890338 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -2,12 +2,13 @@
/*
* internal.h - printk internal definitions
*/
-#include <linux/percpu.h>
#include <linux/console.h>
#include <linux/jump_label.h>
-#include "printk_ringbuffer.h"
+#include <linux/percpu.h>
+#include <linux/types.h>
#if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
+struct ctl_table;
void __init printk_sysctl_init(void);
int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos);
@@ -51,18 +52,11 @@ enum printk_info_flags {
LOG_CONT = 8, /* text is a fragment of a continuation line */
};
+struct printk_ringbuffer;
+struct dev_printk_info;
+
extern struct printk_ringbuffer *prb;
extern bool printk_threads_enabled;
-extern bool have_legacy_console;
-extern bool have_boot_console;
-
-/*
- * Specifies if the console lock/unlock dance is needed for console
- * printing. If @have_boot_console is true, the nbcon consoles will
- * be printed serially along with the legacy consoles because nbcon
- * consoles cannot print simultaneously with boot consoles.
- */
-#define printing_via_unlock (have_legacy_console || have_boot_console)
__printf(4, 0)
int vprintk_store(int facility, int level,
@@ -72,6 +66,9 @@ int vprintk_store(int facility, int level,
__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
+void __printk_safe_enter(void);
+void __printk_safe_exit(void);
+
bool printk_percpu_data_ready(void);
#define printk_safe_enter_irqsave(flags) \
@@ -99,7 +96,7 @@ bool nbcon_alloc(struct console *con);
void nbcon_init(struct console *con);
void nbcon_free(struct console *con);
enum nbcon_prio nbcon_get_default_prio(void);
-void nbcon_atomic_flush_all(void);
+void nbcon_atomic_flush_pending(void);
bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
int cookie, bool use_atomic);
void nbcon_kthread_create(struct console *con);
@@ -173,7 +170,6 @@ static inline void nbcon_kthread_wake(struct console *con)
static inline void nbcon_kthread_wake(struct console *con) { }
static inline void nbcon_kthread_create(struct console *con) { }
#define printk_threads_enabled (false)
-#define printing_via_unlock (false)
/*
* In !PRINTK builds we still export console_sem
@@ -190,7 +186,7 @@ static inline bool nbcon_alloc(struct console *con) { return false; }
static inline void nbcon_init(struct console *con) { }
static inline void nbcon_free(struct console *con) { }
static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; }
-static inline void nbcon_atomic_flush_all(void) { }
+static inline void nbcon_atomic_flush_pending(void) { }
static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
int cookie, bool use_atomic) { return false; }
@@ -199,6 +195,17 @@ static inline bool console_is_usable(struct console *con, short flags,
#endif /* CONFIG_PRINTK */
+extern bool have_boot_console;
+extern bool have_legacy_console;
+
+/*
+ * Specifies if the console lock/unlock dance is needed for console
+ * printing. If @have_boot_console is true, the nbcon consoles will
+ * be printed serially along with the legacy consoles because nbcon
+ * consoles cannot print simultaneously with boot consoles.
+ */
+#define printing_via_unlock (have_legacy_console || have_boot_console)
+
extern struct printk_buffers printk_shared_pbufs;
/**
@@ -233,4 +240,5 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
#ifdef CONFIG_PRINTK
void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
+void console_prepend_replay(struct printk_message *pmsg);
#endif
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index f2d59a0a93e58..92d59c85d43a3 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -2,15 +2,26 @@
// Copyright (C) 2022 Linutronix GmbH, John Ogness
// Copyright (C) 2022 Intel, Thomas Gleixner
-#include <linux/kernel.h>
+#include <linux/atomic.h>
+#include <linux/bug.h>
#include <linux/console.h>
#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/irqflags.h>
#include <linux/kthread.h>
+#include <linux/minmax.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
#include <linux/slab.h>
-#include <linux/serial_core.h>
+#include <linux/smp.h>
+#include <linux/stddef.h>
+#include <linux/string.h>
#include <linux/syscore_ops.h>
-#include "printk_ringbuffer.h"
+#include <linux/types.h>
#include "internal.h"
+#include "printk_ringbuffer.h"
/*
* Printk console printing implementation for consoles which does not depend
* on the legacy style console_lock mechanism.
@@ -176,9 +187,6 @@ void nbcon_seq_force(struct console *con, u64 seq)
u64 valid_seq = max_t(u64, seq, prb_first_valid_seq(prb));
atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __u64seq_to_ulseq(valid_seq));
-
- /* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */
- con->seq = 0;
}
/**
@@ -890,7 +898,7 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
unsigned long con_dropped;
struct nbcon_state cur;
unsigned long dropped;
- bool done = false;
+ unsigned long ulseq;
/*
* The printk buffers are filled within an unsafe section. This
@@ -916,6 +924,28 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
if (dropped && !is_extended)
console_prepend_dropped(&pmsg, dropped);
+ /*
+ * If the previous owner was assigned the same record, this context
+ * has taken over ownership and is replaying the record. Prepend a
+ * message to let the user know the record is replayed.
+ */
+ ulseq = atomic_long_read(&ACCESS_PRIVATE(con, nbcon_prev_seq));
+ if (__ulseq_to_u64seq(prb, ulseq) == pmsg.seq) {
+ console_prepend_replay(&pmsg);
+ } else {
+ /*
+ * Ensure this context is still the owner before trying to
+ * update @nbcon_prev_seq. Otherwise the value in @ulseq may
+ * not be from the previous owner.
+ */
+ nbcon_state_read(con, &cur);
+ if (!nbcon_context_can_proceed(ctxt, &cur))
+ return false;
+
+ atomic_long_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_prev_seq), &ulseq,
+ __u64seq_to_ulseq(pmsg.seq));
+ }
+
if (!nbcon_context_exit_unsafe(ctxt))
return false;
@@ -931,18 +961,26 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
if (use_atomic &&
con->write_atomic) {
- done = con->write_atomic(con, wctxt);
+ con->write_atomic(con, wctxt);
} else if (!use_atomic &&
con->write_thread) {
- done = con->write_thread(con, wctxt);
+ con->write_thread(con, wctxt);
+
+ } else {
+ /*
+ * This function should never be called for legacy consoles.
+ * Handle it as if ownership was lost and try to continue.
+ */
+ WARN_ON_ONCE(1);
+ nbcon_context_release(ctxt);
+ return false;
}
- if (!done) {
+ if (!wctxt->outbuf) {
/*
- * The emit was aborted, probably due to a loss of ownership.
- * Ensure ownership was lost or released before reporting the
- * loss.
+ * Ownership was lost and reacquired by the driver.
+ * Handle it as if ownership was lost and try to continue.
*/
nbcon_context_release(ctxt);
return false;
@@ -987,7 +1025,7 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
*/
static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_context *ctxt)
{
- bool is_usable;
+ bool ret = false;
short flags;
int cookie;
@@ -995,17 +1033,17 @@ static bool nbcon_kthread_should_wakeup(struct console *con, struct nbcon_contex
return true;
cookie = console_srcu_read_lock();
+
flags = console_srcu_read_flags(con);
- is_usable = console_is_usable(con, flags, false);
+ if (console_is_usable(con, flags, false)) {
+ /* Bring the sequence in @ctxt up to date */
+ ctxt->seq = nbcon_seq_read(con);
+
+ ret = prb_read_valid(prb, ctxt->seq, NULL);
+ }
+
console_srcu_read_unlock(cookie);
-
- if (!is_usable)
- return false;
-
- /* Bring the sequence in @ctxt up to date */
- ctxt->seq = nbcon_seq_read(con);
-
- return prb_read_valid(prb, ctxt->seq, NULL);
+ return ret;
}
/**
@@ -1056,7 +1094,7 @@ static int nbcon_kthread_func(void *__console)
con_flags = console_srcu_read_flags(con);
if (console_is_usable(con, con_flags, false)) {
- con->driver_enter(con, &flags);
+ con->device_lock(con, &flags);
/*
* Ensure this stays on the CPU to make handover and
@@ -1075,7 +1113,7 @@ static int nbcon_kthread_func(void *__console)
}
}
- con->driver_exit(con, flags);
+ con->device_unlock(con, flags);
}
console_srcu_read_unlock(cookie);
@@ -1166,12 +1204,11 @@ static __ref unsigned int *nbcon_get_cpu_emergency_nesting(void)
/**
* nbcon_emit_one - Print one record for an nbcon console using the
* specified callback
- * @wctxt: An initialized write context struct to use
- * for this context
+ * @wctxt: An initialized write context struct to use for this context
* @use_atomic: True if the write_atomic callback is to be used
*
- * Return: False if the given console could not print a record or there
- * are no more records to print, otherwise true.
+ * Return: False if it is known there are no more records to print,
+ * otherwise true.
*
* This is an internal helper to handle the locking of the console before
* calling nbcon_emit_next_record().
@@ -1181,7 +1218,7 @@ static bool nbcon_emit_one(struct nbcon_write_context *wctxt, bool use_atomic)
struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
if (!nbcon_context_try_acquire(ctxt))
- return false;
+ return true;
/*
* nbcon_emit_next_record() returns false when the console was
@@ -1189,7 +1226,7 @@ static bool nbcon_emit_one(struct nbcon_write_context *wctxt, bool use_atomic)
* longer valid.
*/
if (!nbcon_emit_next_record(wctxt, use_atomic))
- return false;
+ return true;
nbcon_context_release(ctxt);
@@ -1229,8 +1266,9 @@ enum nbcon_prio nbcon_get_default_prio(void)
* @cookie: The cookie from the SRCU read lock.
* @use_atomic: True if the write_atomic callback is to be used
*
- * Context: Any context which could not be migrated to another CPU.
- * Return: True if a record could be printed, otherwise false.
+ * Context: Any context except NMI.
+ * Return: False if the given console has no next record to print,
+ * otherwise true.
*
* This function is meant to be called by console_flush_all() to print records
* on nbcon consoles from legacy context (printing via console unlocking).
@@ -1241,8 +1279,8 @@ bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
{
struct nbcon_write_context wctxt = { };
struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt);
- bool progress = false;
unsigned long flags;
+ bool progress;
*handover = false;
@@ -1261,34 +1299,78 @@ bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,
*handover = console_lock_spinning_disable_and_check(cookie);
printk_safe_exit_irqrestore(flags);
} else {
- con->driver_enter(con, &flags);
+ con->device_lock(con, &flags);
cant_migrate();
ctxt->prio = nbcon_get_default_prio();
progress = nbcon_emit_one(&wctxt, use_atomic);
- con->driver_exit(con, flags);
+ con->device_unlock(con, flags);
}
return progress;
}
/**
- * __nbcon_atomic_flush_all - Flush all nbcon consoles using their
+ * __nbcon_atomic_flush_pending_con - Flush specified nbcon console using its
+ * write_atomic() callback
+ * @con: The nbcon console to flush
+ * @stop_seq: Flush up until this record
+ * @allow_unsafe_takeover: True, to allow unsafe hostile takeovers
+ *
+ * Return: True if taken over while printing. Otherwise false.
+ *
+ * If flushing up to @stop_seq was not successful, it only makes sense for the
+ * caller to try again when true was returned. When false is returned, either
+ * there are no more records available to read or this context is not allowed
+ * to acquire the console.
+ */
+static bool __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq,
+ bool allow_unsafe_takeover)
+{
+ struct nbcon_write_context wctxt = { };
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt);
+
+ ctxt->console = con;
+ ctxt->spinwait_max_us = 2000;
+ ctxt->prio = nbcon_get_default_prio();
+ ctxt->allow_unsafe_takeover = allow_unsafe_takeover;
+
+ if (!nbcon_context_try_acquire(ctxt))
+ return false;
+
+ while (nbcon_seq_read(con) < stop_seq) {
+ /*
+ * nbcon_emit_next_record() returns false when the console was
+ * handed over or taken over. In both cases the context is no
+ * longer valid.
+ */
+ if (!nbcon_emit_next_record(&wctxt, true))
+ return true;
+
+ if (!ctxt->backlog)
+ break;
+ }
+
+ nbcon_context_release(ctxt);
+
+ return false;
+}
+
+/**
+ * __nbcon_atomic_flush_pending - Flush all nbcon consoles using their
* write_atomic() callback
* @stop_seq: Flush up until this record
* @allow_unsafe_takeover: True, to allow unsafe hostile takeovers
*/
-static void __nbcon_atomic_flush_all(u64 stop_seq, bool allow_unsafe_takeover)
+static void __nbcon_atomic_flush_pending(u64 stop_seq, bool allow_unsafe_takeover)
{
- struct nbcon_write_context wctxt = { };
- struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt);
struct console *con;
- bool any_progress;
+ bool should_retry;
int cookie;
do {
- any_progress = false;
+ should_retry = false;
cookie = console_srcu_read_lock();
for_each_console_srcu(con) {
@@ -1304,11 +1386,6 @@ static void __nbcon_atomic_flush_all(u64 stop_seq, bool allow_unsafe_takeover)
if (nbcon_seq_read(con) >= stop_seq)
continue;
- memset(ctxt, 0, sizeof(*ctxt));
- ctxt->console = con;
- ctxt->spinwait_max_us = 2000;
- ctxt->allow_unsafe_takeover = allow_unsafe_takeover;
-
/*
* Atomic flushing does not use console driver
* synchronization (i.e. it does not hold the port
@@ -1316,33 +1393,28 @@ static void __nbcon_atomic_flush_all(u64 stop_seq, bool allow_unsafe_takeover)
* disabled to avoid being interrupted and then
* calling into a driver that will deadlock trying
* acquire console ownership.
- *
- * This also disables migration in order to get the
- * current CPU priority.
*/
local_irq_save(irq_flags);
- ctxt->prio = nbcon_get_default_prio();
-
- any_progress |= nbcon_emit_one(&wctxt, true);
-
+ should_retry |= __nbcon_atomic_flush_pending_con(con, stop_seq,
+ allow_unsafe_takeover);
local_irq_restore(irq_flags);
}
console_srcu_read_unlock(cookie);
- } while (any_progress);
+ } while (should_retry);
}
/**
- * nbcon_atomic_flush_all - Flush all nbcon consoles using their
+ * nbcon_atomic_flush_pending - Flush all nbcon consoles using their
* write_atomic() callback
*
* Flush the backlog up through the currently newest record. Any new
* records added while flushing will not be flushed. This is to avoid
* one CPU printing unbounded because other CPUs continue to add records.
*/
-void nbcon_atomic_flush_all(void)
+void nbcon_atomic_flush_pending(void)
{
- __nbcon_atomic_flush_all(prb_next_reserve_seq(prb), false);
+ __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb), false);
}
/**
@@ -1354,7 +1426,7 @@ void nbcon_atomic_flush_all(void)
*/
void nbcon_atomic_flush_unsafe(void)
{
- __nbcon_atomic_flush_all(prb_next_reserve_seq(prb), true);
+ __nbcon_atomic_flush_pending(prb_next_reserve_seq(prb), true);
}
/**
@@ -1397,8 +1469,10 @@ void nbcon_cpu_emergency_exit(void)
WARN_ON_ONCE(*cpu_emergency_nesting == 0);
- if (*cpu_emergency_nesting == 1)
+ if (*cpu_emergency_nesting == 1) {
+ nbcon_atomic_flush_pending();
do_trigger_flush = true;
+ }
/* Undo the nesting count of nbcon_cpu_emergency_enter(). */
(*cpu_emergency_nesting)--;
@@ -1517,8 +1591,6 @@ bool nbcon_alloc(struct console *con)
*
* nbcon_alloc() *must* be called and succeed before this function
* is called.
- *
- * This function expects that the legacy @con->seq has been set.
*/
void nbcon_init(struct console *con)
{
@@ -1529,7 +1601,8 @@ void nbcon_init(struct console *con)
rcuwait_init(&con->rcuwait);
init_irq_work(&con->irq_work, nbcon_irq_work);
- nbcon_seq_force(con, con->seq);
+ nbcon_seq_force(con, 0);
+ atomic_long_set(&ACCESS_PRIVATE(con, nbcon_prev_seq), -1UL);
nbcon_state_set(con, &state);
nbcon_kthread_create(con);
}
@@ -1552,87 +1625,54 @@ void nbcon_free(struct console *con)
con->pbufs = NULL;
}
-static inline bool uart_is_nbcon(struct uart_port *up)
-{
- int cookie;
- bool ret;
-
- if (!uart_console(up))
- return false;
-
- cookie = console_srcu_read_lock();
- ret = (console_srcu_read_flags(up->cons) & CON_NBCON);
- console_srcu_read_unlock(cookie);
- return ret;
-}
-
/**
- * uart_nbcon_acquire - The second half of the port locking wrapper
- * @up: The uart port whose @lock was locked
+ * nbcon_driver_acquire - Acquire nbcon console and enter unsafe section
+ * @con: The nbcon console to acquire
*
- * The uart_port_lock() wrappers will first lock the spin_lock @up->lock.
- * Then this function is called to implement nbcon-specific processing.
+ * Context: Any context which could not be migrated to another CPU.
*
- * If @up is an nbcon console, this console will be acquired and marked as
- * unsafe. Otherwise this function does nothing.
+ * Console drivers will usually use their own internal synchronization
+ * mechasism to synchronize between console printing and non-printing
+ * activities (such as setting baud rates). However, nbcon console drivers
+ * supporting atomic consoles may also want to mark unsafe sections when
+ * performing non-printing activities.
*
- * nbcon consoles acquired via the port lock wrapper always use priority
- * NBCON_PRIO_NORMAL.
+ * This function acquires the nbcon console using priority NBCON_PRIO_NORMAL
+ * and marks it unsafe for handover/takeover.
+ *
+ * Console drivers using this function must have provided @nbcon_drvdata in
+ * their struct console, which is used to track ownership and state
+ * information.
*/
-void uart_nbcon_acquire(struct uart_port *up)
+void nbcon_driver_acquire(struct console *con)
{
- struct console *con = up->cons;
- struct nbcon_context ctxt;
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(con->nbcon_drvdata, ctxt);
- if (!uart_is_nbcon(up))
- return;
-
- WARN_ON_ONCE(up->nbcon_locked_port);
+ cant_migrate();
do {
do {
- memset(&ctxt, 0, sizeof(ctxt));
- ctxt.console = con;
- ctxt.prio = NBCON_PRIO_NORMAL;
- } while (!nbcon_context_try_acquire(&ctxt));
+ memset(ctxt, 0, sizeof(*ctxt));
+ ctxt->console = con;
+ ctxt->prio = NBCON_PRIO_NORMAL;
+ } while (!nbcon_context_try_acquire(ctxt));
- } while (!nbcon_context_enter_unsafe(&ctxt));
-
- up->nbcon_locked_port = true;
+ } while (!nbcon_context_enter_unsafe(ctxt));
}
-EXPORT_SYMBOL_GPL(uart_nbcon_acquire);
+EXPORT_SYMBOL_GPL(nbcon_driver_acquire);
/**
- * uart_nbcon_release - The first half of the port unlocking wrapper
- * @up: The uart port whose @lock is about to be unlocked
- *
- * The uart_port_unlock() wrappers will first call this function to implement
- * nbcon-specific processing. Then afterwards the uart_port_unlock() wrappers
- * will unlock the spin_lock @up->lock.
- *
- * If @up is an nbcon console, the console will be marked as safe and
- * released. Otherwise this function does nothing.
- *
- * nbcon consoles acquired via the port lock wrapper always use priority
- * NBCON_PRIO_NORMAL.
+ * nbcon_driver_release - Exit unsafe section and release the nbcon console
+ * @con: The nbcon console acquired in nbcon_driver_acquire()
*/
-void uart_nbcon_release(struct uart_port *up)
+void nbcon_driver_release(struct console *con)
{
- struct console *con = up->cons;
- struct nbcon_context ctxt = {
- .console = con,
- .prio = NBCON_PRIO_NORMAL,
- };
+ struct nbcon_context *ctxt = &ACCESS_PRIVATE(con->nbcon_drvdata, ctxt);
- if (!up->nbcon_locked_port)
- return;
-
- if (nbcon_context_exit_unsafe(&ctxt))
- nbcon_context_release(&ctxt);
-
- up->nbcon_locked_port = false;
+ if (nbcon_context_exit_unsafe(ctxt))
+ nbcon_context_release(ctxt);
}
-EXPORT_SYMBOL_GPL(uart_nbcon_release);
+EXPORT_SYMBOL_GPL(nbcon_driver_release);
/**
* printk_kthread_shutdown - shutdown all threaded printers
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index e29f77f4f8b46..2be1157e8169c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -200,8 +200,8 @@ DEFINE_STATIC_KEY_FALSE(force_printkthreads_key);
static int __init setup_forced_printkthreads(char *arg)
{
- static_branch_enable(&force_printkthreads_key);
- return 0;
+ static_branch_enable(&force_printkthreads_key);
+ return 0;
}
early_param("threadprintk", setup_forced_printkthreads);
#endif
@@ -486,7 +486,7 @@ bool have_legacy_console;
* synchronous printing of legacy consoles will not occur during panic until
* the backtrace has been stored to the ringbuffer.
*/
-bool have_nbcon_console;
+static bool have_nbcon_console;
/*
* Specifies if a boot console is registered. If boot consoles are present,
@@ -2347,11 +2347,15 @@ static bool legacy_allow_panic_sync;
/*
* This acts as a one-way switch to allow legacy consoles to print from
- * the printk() caller context on a panic CPU.
+ * the printk() caller context on a panic CPU. It also attempts to flush
+ * the legacy consoles in this context.
*/
void printk_legacy_allow_panic_sync(void)
{
legacy_allow_panic_sync = true;
+
+ if (printing_via_unlock && !in_nmi() && console_trylock())
+ console_unlock();
}
asmlinkage int vprintk_emit(int facility, int level,
@@ -2384,7 +2388,7 @@ asmlinkage int vprintk_emit(int facility, int level,
printed_len = vprintk_store(facility, level, dev_info, fmt, args);
- if (!have_boot_console && have_nbcon_console) {
+ if (have_nbcon_console && !have_boot_console) {
bool is_panic_context = this_cpu_in_panic();
/*
@@ -2417,7 +2421,7 @@ asmlinkage int vprintk_emit(int facility, int level,
if (is_panic_context ||
!printk_threads_enabled ||
(system_state > SYSTEM_RUNNING)) {
- nbcon_atomic_flush_all();
+ nbcon_atomic_flush_pending();
}
}
@@ -2436,19 +2440,15 @@ asmlinkage int vprintk_emit(int facility, int level,
preempt_disable();
/*
- * Do not emit for EMERGENCY priority. The console will be
+ * Try to acquire and then immediately release the console
+ * semaphore. The release will print out buffers. With the
+ * spinning variant, this context tries to take over the
+ * printing from another printing context.
+ *
+ * Skip it in EMERGENCY priority. The console will be
* explicitly flushed when exiting the emergency section.
*/
- if (nbcon_get_default_prio() == NBCON_PRIO_EMERGENCY) {
- do_trylock_unlock = false;
- } else {
- /*
- * Try to acquire and then immediately release the
- * console semaphore. The release will print out
- * buffers. With the spinning variant, this context
- * tries to take over the printing from another
- * printing context.
- */
+ if (nbcon_get_default_prio() != NBCON_PRIO_EMERGENCY) {
if (console_trylock_spinning())
console_unlock();
}
@@ -2838,30 +2838,25 @@ static void __console_unlock(void)
#ifdef CONFIG_PRINTK
/*
- * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message". This
- * is achieved by shifting the existing message over and inserting the dropped
- * message.
+ * Prepend the message in @pmsg->pbufs->outbuf with the message in
+ * @pmsg->pbufs->scratchbuf. This is achieved by shifting the existing message
+ * over and inserting the scratchbuf message.
*
* @pmsg is the printk message to prepend.
*
- * @dropped is the dropped count to report in the dropped message.
+ * @len is the length of the message in @pmsg->pbufs->scratchbuf.
*
* If the message text in @pmsg->pbufs->outbuf does not have enough space for
- * the dropped message, the message text will be sufficiently truncated.
+ * the scratchbuf message, the message text will be sufficiently truncated.
*
* If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
*/
-void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
+static void __console_prepend_scratch(struct printk_message *pmsg, size_t len)
{
struct printk_buffers *pbufs = pmsg->pbufs;
- const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
const size_t outbuf_sz = sizeof(pbufs->outbuf);
char *scratchbuf = &pbufs->scratchbuf[0];
char *outbuf = &pbufs->outbuf[0];
- size_t len;
-
- len = scnprintf(scratchbuf, scratchbuf_sz,
- "** %lu printk messages dropped **\n", dropped);
/*
* Make sure outbuf is sufficiently large before prepending.
@@ -2883,6 +2878,46 @@ void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
pmsg->outbuf_len += len;
}
+/*
+ * Prepend the message in @pmsg->pbufs->outbuf with a "dropped message".
+ * @pmsg->outbuf_len is updated appropriately.
+ *
+ * @pmsg is the printk message to prepend.
+ *
+ * @dropped is the dropped count to report in the dropped message.
+ */
+void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
+{
+ struct printk_buffers *pbufs = pmsg->pbufs;
+ const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
+ char *scratchbuf = &pbufs->scratchbuf[0];
+ size_t len;
+
+ len = scnprintf(scratchbuf, scratchbuf_sz,
+ "** %lu printk messages dropped **\n", dropped);
+
+ __console_prepend_scratch(pmsg, len);
+}
+
+/*
+ * Prepend the message in @pmsg->pbufs->outbuf with a "replay message".
+ * @pmsg->outbuf_len is updated appropriately.
+ *
+ * @pmsg is the printk message to prepend.
+ */
+void console_prepend_replay(struct printk_message *pmsg)
+{
+ struct printk_buffers *pbufs = pmsg->pbufs;
+ const size_t scratchbuf_sz = sizeof(pbufs->scratchbuf);
+ char *scratchbuf = &pbufs->scratchbuf[0];
+ size_t len;
+
+ len = scnprintf(scratchbuf, scratchbuf_sz,
+ "** replaying previous printk message **\n");
+
+ __console_prepend_scratch(pmsg, len);
+}
+
/*
* Read and format the specified record (or a later record if the specified
* record is not available).
@@ -2962,7 +2997,7 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
static inline void printk_legacy_lock_map_acquire_try(void) { }
static inline void printk_legacy_lock_map_release(void) { }
#else
-DEFINE_WAIT_OVERRIDE_MAP(printk_legacy_map, LD_WAIT_SLEEP);
+static DEFINE_WAIT_OVERRIDE_MAP(printk_legacy_map, LD_WAIT_SLEEP);
static inline void printk_legacy_lock_map_acquire_try(void)
{
@@ -3136,7 +3171,6 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove
printk_seq = nbcon_seq_read(con);
} else {
progress = console_emit_next_record(con, handover, cookie);
-
printk_seq = con->seq;
}
@@ -3375,7 +3409,7 @@ void console_flush_on_panic(enum con_flush_mode mode)
console_srcu_read_unlock(cookie);
}
- nbcon_atomic_flush_all();
+ nbcon_atomic_flush_pending();
if (printing_via_unlock)
console_flush_all(false, &next_seq, &handover);
@@ -3634,6 +3668,7 @@ static void try_enable_default_console(struct console *newcon)
newcon->flags |= CON_CONSDEV;
}
+/* Set @newcon->seq to the first record this console should print. */
static void console_init_seq(struct console *newcon, bool bootcon_registered)
{
struct console *con;
@@ -3733,6 +3768,7 @@ void register_console(struct console *newcon)
struct console *con;
bool bootcon_registered = false;
bool realcon_registered = false;
+ unsigned long flags;
int err;
console_list_lock();
@@ -3815,6 +3851,14 @@ void register_console(struct console *newcon)
if (newcon->flags & CON_NBCON) {
have_nbcon_console = true;
nbcon_init(newcon);
+
+ /*
+ * nbcon consoles have their own sequence counter. The legacy
+ * sequence counter is reset so that it is clear it is not
+ * being used.
+ */
+ nbcon_seq_force(newcon, newcon->seq);
+ newcon->seq = 0;
} else {
have_legacy_console = true;
nbcon_legacy_kthread_create();
@@ -3823,6 +3867,19 @@ void register_console(struct console *newcon)
if (newcon->flags & CON_BOOT)
have_boot_console = true;
+ /*
+ * If another context is actively using the hardware of this new
+ * console, it will not be aware of the nbcon synchronization. This
+ * is a risk that two contexts could access the hardware
+ * simultaneously if this new console is used for atomic printing
+ * and the other context is still using the hardware.
+ *
+ * Use the driver synchronization to ensure that the hardware is not
+ * in use while this new console transitions to being registered.
+ */
+ if ((newcon->flags & CON_NBCON) && newcon->write_atomic)
+ newcon->device_lock(newcon, &flags);
+
/*
* Put this console in the list - keep the
* preferred driver at the head of the list.
@@ -3847,6 +3904,10 @@ void register_console(struct console *newcon)
* register_console() completes.
*/
+ /* This new console is now registered. */
+ if ((newcon->flags & CON_NBCON) && newcon->write_atomic)
+ newcon->device_unlock(newcon, flags);
+
console_sysfs_notify();
/*
@@ -3941,11 +4002,11 @@ static int unregister_console_locked(struct console *console)
found_legacy_con = true;
}
if (!found_boot_con)
- have_boot_console = false;
+ have_boot_console = found_boot_con;
if (!found_legacy_con)
- have_legacy_console = false;
+ have_legacy_console = found_legacy_con;
if (!found_nbcon_con)
- have_nbcon_console = false;
+ have_nbcon_console = found_nbcon_con;
/*
* When the last boot console unregisters, start up the
@@ -4150,6 +4211,13 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
locked = true;
}
+ /*
+ * Ensure the compiler does not optimize @locked to be
+ * @printing_via_unlock since the latter can change at any
+ * time.
+ */
+ barrier();
+
cookie = console_srcu_read_lock();
for_each_console_srcu(c) {
if (con && con != c)
@@ -4260,6 +4328,7 @@ static void __wake_up_klogd(int val)
return;
preempt_disable();
+
/*
* Guarantee any new records can be seen by tasks preparing to wait
* before this context checks if the wait queue is empty.
@@ -4271,11 +4340,22 @@ static void __wake_up_klogd(int val)
*
* This pairs with devkmsg_read:A and syslog_print:A.
*/
- if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */
- (val & PRINTK_PENDING_OUTPUT)) {
+ if (!wq_has_sleeper(&log_wait)) /* LMM(__wake_up_klogd:A) */
+ val &= ~PRINTK_PENDING_WAKEUP;
+
+ /*
+ * Simple read is safe. register_console() would flush a newly
+ * registered legacy console when writing the message about it
+ * being enabled.
+ */
+ if (!printing_via_unlock)
+ val &= ~PRINTK_PENDING_OUTPUT;
+
+ if (val) {
this_cpu_or(printk_pending, val);
irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
}
+
preempt_enable();
}
@@ -4312,11 +4392,7 @@ void defer_console_output(void)
* New messages may have been added directly to the ringbuffer
* using vprintk_store(), so wake any waiters as well.
*/
- int val = PRINTK_PENDING_WAKEUP;
-
- if (printing_via_unlock)
- val |= PRINTK_PENDING_OUTPUT;
- __wake_up_klogd(val);
+ __wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT);
}
void printk_trigger_flush(void)
diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 52626d0f1fa37..bd2a892deac1a 100644
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -5,6 +5,8 @@
#include <linux/atomic.h>
#include <linux/dev_printk.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
/*
* Meta information about each stored message.
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 8d9408d653de5..4421ccac31133 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -29,13 +29,13 @@ void __printk_safe_exit(void)
void __printk_deferred_enter(void)
{
cant_migrate();
- this_cpu_inc(printk_context);
+ __printk_safe_enter();
}
void __printk_deferred_exit(void)
{
cant_migrate();
- this_cpu_dec(printk_context);
+ __printk_safe_exit();
}
asmlinkage int vprintk(const char *fmt, va_list args)
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 8107f818455da..b17130b7e522d 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -7,6 +7,7 @@
* Authors: Paul E. McKenney <paulmck@...ux.ibm.com>
*/
+#include <linux/console.h>
#include <linux/lockdep.h>
static void rcu_exp_handler(void *unused);
@@ -636,6 +637,9 @@ static void synchronize_rcu_expedited_wait(void)
return;
if (rcu_stall_is_suppressed())
continue;
+
+ nbcon_cpu_emergency_enter();
+
j = jiffies;
rcu_stall_notifier_call_chain(RCU_STALL_NOTIFY_EXP, (void *)(j - jiffies_start));
trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
@@ -689,6 +693,9 @@ static void synchronize_rcu_expedited_wait(void)
rcu_exp_print_detail_task_stall_rnp(rnp);
}
jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3;
+
+ nbcon_cpu_emergency_exit();
+
panic_on_rcu_stall();
}
}
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 5887c00e67389..f4d73ca20c768 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -7,9 +7,9 @@
* Author: Paul E. McKenney <paulmck@...ux.ibm.com>
*/
+#include <linux/console.h>
#include <linux/kvm_para.h>
#include <linux/rcu_notifier.h>
-#include <linux/console.h>
//////////////////////////////////////////////////////////////////////////////
//
@@ -658,11 +658,11 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
rcu_check_gp_kthread_expired_fqs_timer();
rcu_check_gp_kthread_starvation();
+ nbcon_cpu_emergency_exit();
+
panic_on_rcu_stall();
rcu_force_quiescent_state(); /* Kick them all. */
-
- nbcon_cpu_emergency_exit();
}
static void print_cpu_stall(unsigned long gps)
@@ -680,6 +680,8 @@ static void print_cpu_stall(unsigned long gps)
if (rcu_stall_is_suppressed())
return;
+ nbcon_cpu_emergency_enter();
+
/*
* OK, time to rat on ourselves...
* See Documentation/RCU/stallwarn.rst for info on how to debug
@@ -708,6 +710,8 @@ static void print_cpu_stall(unsigned long gps)
jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ nbcon_cpu_emergency_exit();
+
panic_on_rcu_stall();
/*
diff --git a/localversion-rt b/localversion-rt
index 22746d6390a42..d79dde624aaac 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt9
+-rt10
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