[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20230302195618.156940-11-john.ogness@linutronix.de>
Date: Thu, 2 Mar 2023 21:02:10 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [PATCH printk v1 10/18] printk: nobkl: Add emit function and callback functions for atomic printing
From: Thomas Gleixner <tglx@...utronix.de>
Implement an emit function for non-BKL consoles to output printk
messages. It utilizes the lockless printk_get_next_message() and
console_prepend_dropped() functions to retrieve/build the output
message. The emit function includes the required safety points to
check for handover/takeover and calls a new write_atomic callback
of the console driver to output the message. It also includes proper
handling for updating the non-BKL console sequence number.
Co-developed-by: John Ogness <john.ogness@...utronix.de>
Signed-off-by: John Ogness <john.ogness@...utronix.de>
Signed-off-by: Thomas Gleixner (Intel) <tglx@...utronix.de>
---
include/linux/console.h | 8 +++
kernel/printk/internal.h | 9 +++
kernel/printk/printk.c | 12 ++--
kernel/printk/printk_nobkl.c | 121 ++++++++++++++++++++++++++++++++++-
4 files changed, 141 insertions(+), 9 deletions(-)
diff --git a/include/linux/console.h b/include/linux/console.h
index 0779757cb917..15f71ccfcd9d 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -250,10 +250,12 @@ struct printk_buffers;
* @newseq: The sequence number for progress
* @prio: Priority of the context
* @pbufs: Pointer to the text buffer for this context
+ * @dropped: Dropped counter for the current context
* @thread: The acquire is printk thread context
* @hostile: Hostile takeover requested. Cleared on normal
* acquire or friendly handover
* @spinwait: Spinwait on acquire if possible
+ * @backlog: Ringbuffer has pending records
*/
struct cons_context {
struct console *console;
@@ -266,9 +268,11 @@ struct cons_context {
unsigned int spinwait_max_us;
enum cons_prio prio;
struct printk_buffers *pbufs;
+ unsigned long dropped;
unsigned int thread : 1;
unsigned int hostile : 1;
unsigned int spinwait : 1;
+ unsigned int backlog : 1;
};
/**
@@ -310,6 +314,7 @@ struct cons_context_data;
* @atomic_state: State array for NOBKL consoles; real and handover
* @atomic_seq: Sequence for record tracking (32bit only)
* @thread_pbufs: Pointer to thread private buffer
+ * @write_atomic: Write callback for atomic context
* @pcpu_data: Pointer to percpu context data
*/
struct console {
@@ -337,6 +342,9 @@ struct console {
atomic_t __private atomic_seq;
#endif
struct printk_buffers *thread_pbufs;
+
+ bool (*write_atomic)(struct console *con, struct cons_write_context *wctxt);
+
struct cons_context_data __percpu *pcpu_data;
};
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 15a412065327..13dd0ce23c37 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -133,3 +133,12 @@ struct printk_message {
struct cons_context_data {
struct printk_buffers pbufs;
};
+
+#ifdef CONFIG_PRINTK
+
+bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
+ bool is_extended, bool may_supress);
+void console_prepend_dropped(struct printk_message *pmsg,
+ unsigned long dropped);
+
+#endif
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 21b31183ff2b..eab0358baa6f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -715,9 +715,6 @@ static ssize_t msg_print_ext_body(char *buf, size_t size,
return len;
}
-static bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
- bool is_extended, bool may_supress);
-
/* /dev/kmsg - userspace message inject/listen interface */
struct devkmsg_user {
atomic64_t seq;
@@ -2786,7 +2783,7 @@ static void __console_unlock(void)
* If @pmsg->pbufs->outbuf is modified, @pmsg->outbuf_len is updated.
*/
#ifdef CONFIG_PRINTK
-static void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped)
+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);
@@ -2818,7 +2815,8 @@ static void console_prepend_dropped(struct printk_message *pmsg, unsigned long d
pmsg->outbuf_len += len;
}
#else
-#define console_prepend_dropped(pmsg, dropped)
+static inline void console_prepend_dropped(struct printk_message *pmsg,
+ unsigned long dropped) { }
#endif /* CONFIG_PRINTK */
/*
@@ -2840,8 +2838,8 @@ static void console_prepend_dropped(struct printk_message *pmsg, unsigned long d
* of @pmsg are valid. (See the documentation of struct printk_message
* for information about the @pmsg fields.)
*/
-static bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
- bool is_extended, bool may_suppress)
+bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
+ bool is_extended, bool may_suppress)
{
static int panic_console_dropped;
diff --git a/kernel/printk/printk_nobkl.c b/kernel/printk/printk_nobkl.c
index 3318a79a150a..5c591bced1be 100644
--- a/kernel/printk/printk_nobkl.c
+++ b/kernel/printk/printk_nobkl.c
@@ -317,7 +317,7 @@ static void cons_context_set_seq(struct cons_context *ctxt)
* invalid. Caller has to reacquire the console.
*/
#ifdef CONFIG_64BIT
-static bool __maybe_unused cons_seq_try_update(struct cons_context *ctxt)
+static bool cons_seq_try_update(struct cons_context *ctxt)
{
struct console *con = ctxt->console;
struct cons_state old;
@@ -346,7 +346,7 @@ static bool __maybe_unused cons_seq_try_update(struct cons_context *ctxt)
}
#else
static bool cons_release(struct cons_context *ctxt);
-static bool __maybe_unused cons_seq_try_update(struct cons_context *ctxt)
+static bool cons_seq_try_update(struct cons_context *ctxt)
{
struct console *con = ctxt->console;
struct cons_state state;
@@ -1086,6 +1086,123 @@ bool console_exit_unsafe(struct cons_write_context *wctxt)
return __console_update_unsafe(wctxt, false);
}
+/**
+ * cons_get_record - Fill the buffer with the next pending ringbuffer record
+ * @wctxt: The write context which will be handed to the write function
+ *
+ * Returns: True if there are records available. If the next record should
+ * be printed, the output buffer is filled and @wctxt->outbuf
+ * points to the text to print. If @wctxt->outbuf is NULL after
+ * the call, the record should not be printed but the caller must
+ * still update the console sequence number.
+ *
+ * False means that there are no pending records anymore and the
+ * printing can stop.
+ */
+static bool cons_get_record(struct cons_write_context *wctxt)
+{
+ struct cons_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
+ struct console *con = ctxt->console;
+ bool is_extended = console_srcu_read_flags(con) & CON_EXTENDED;
+ struct printk_message pmsg = {
+ .pbufs = ctxt->pbufs,
+ };
+
+ if (!printk_get_next_message(&pmsg, ctxt->newseq, is_extended, true))
+ return false;
+
+ ctxt->newseq = pmsg.seq;
+ ctxt->dropped += pmsg.dropped;
+
+ if (pmsg.outbuf_len == 0) {
+ wctxt->outbuf = NULL;
+ } else {
+ if (ctxt->dropped && !is_extended)
+ console_prepend_dropped(&pmsg, ctxt->dropped);
+ wctxt->outbuf = &pmsg.pbufs->outbuf[0];
+ }
+
+ wctxt->len = pmsg.outbuf_len;
+
+ return true;
+}
+
+/**
+ * cons_emit_record - Emit record in the acquired context
+ * @wctxt: The write context that will be handed to the write function
+ *
+ * Returns: False if the operation was aborted (takeover or handover).
+ * True otherwise
+ *
+ * When false is returned, the caller is not allowed to touch console state.
+ * The console is owned by someone else. If the caller wants to print more
+ * it has to reacquire the console first.
+ *
+ * When true is returned, @wctxt->ctxt.backlog indicates whether there are
+ * still records pending in the ringbuffer,
+ */
+static int __maybe_unused cons_emit_record(struct cons_write_context *wctxt)
+{
+ struct cons_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
+ struct console *con = ctxt->console;
+ bool done = false;
+
+ /*
+ * @con->dropped is not protected in case of hostile takeovers so
+ * the update below is racy. Annotate it accordingly.
+ */
+ ctxt->dropped = data_race(READ_ONCE(con->dropped));
+
+ /* Fill the output buffer with the next record */
+ ctxt->backlog = cons_get_record(wctxt);
+ if (!ctxt->backlog)
+ return true;
+
+ /* Safety point. Don't touch state in case of takeover */
+ if (!console_can_proceed(wctxt))
+ return false;
+
+ /* Counterpart to the read above */
+ WRITE_ONCE(con->dropped, ctxt->dropped);
+
+ /*
+ * In case of skipped records, Update sequence state in @con.
+ */
+ if (!wctxt->outbuf)
+ goto update;
+
+ /* Tell the driver about potential unsafe state */
+ wctxt->unsafe = ctxt->state.unsafe;
+
+ if (!ctxt->thread && con->write_atomic) {
+ done = con->write_atomic(con, wctxt);
+ } else {
+ cons_release(ctxt);
+ WARN_ON_ONCE(1);
+ return false;
+ }
+
+ /* If not done, the write was aborted due to takeover */
+ if (!done)
+ return false;
+
+ /* If there was a dropped message, it has now been output. */
+ if (ctxt->dropped) {
+ ctxt->dropped = 0;
+ /* Counterpart to the read above */
+ WRITE_ONCE(con->dropped, ctxt->dropped);
+ }
+update:
+ ctxt->newseq++;
+ /*
+ * The sequence update attempt is not part of console_release()
+ * because in panic situations the console is not released by
+ * the panic CPU until all records are written. On 32bit the
+ * sequence is separate from state anyway.
+ */
+ return cons_seq_try_update(ctxt);
+}
+
/**
* cons_nobkl_init - Initialize the NOBKL console specific data
* @con: Console to initialize
--
2.30.2
Powered by blists - more mailing lists