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Message-Id: <20210330153512.1182-4-john.ogness@linutronix.de>
Date: Tue, 30 Mar 2021 17:35:10 +0200
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Ingo Molnar <mingo@...hat.com>, Marc Zyngier <maz@...nel.org>,
Valentin Schneider <valentin.schneider@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Rapoport <rppt@...nel.org>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Anshuman Khandual <anshuman.khandual@....com>,
Leonardo Bras <leobras.c@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...nel.org>,
Will Deacon <will@...nel.org>,
Frederic Weisbecker <frederic@...nel.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Masahiro Yamada <masahiroy@...nel.org>,
Nathan Chancellor <nathan@...nel.org>,
Alexei Starovoitov <ast@...nel.org>,
Kees Cook <keescook@...omium.org>,
Nick Terrell <terrelln@...com>,
David Howells <dhowells@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH printk v2 3/5] printk: remove NMI tracking
All NMI contexts are handled the same as the safe context: store the
message and defer printing. There is no need to have special NMI
context tracking for this. Using in_nmi() is enough.
Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
arch/arm/kernel/smp.c | 2 --
arch/powerpc/kexec/crash.c | 3 ---
include/linux/hardirq.h | 2 --
include/linux/printk.h | 12 ------------
init/Kconfig | 5 -----
kernel/printk/internal.h | 6 ------
kernel/printk/printk_safe.c | 37 +------------------------------------
kernel/trace/trace.c | 2 --
8 files changed, 1 insertion(+), 68 deletions(-)
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 5c48eb4fd0e5..77a720c1f402 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -671,9 +671,7 @@ static void do_handle_IPI(int ipinr)
break;
case IPI_CPU_BACKTRACE:
- printk_nmi_enter();
nmi_cpu_backtrace(get_irq_regs());
- printk_nmi_exit();
break;
default:
diff --git a/arch/powerpc/kexec/crash.c b/arch/powerpc/kexec/crash.c
index c9a889880214..d488311efab1 100644
--- a/arch/powerpc/kexec/crash.c
+++ b/arch/powerpc/kexec/crash.c
@@ -311,9 +311,6 @@ void default_machine_crash_shutdown(struct pt_regs *regs)
unsigned int i;
int (*old_handler)(struct pt_regs *regs);
- /* Avoid hardlocking with irresponsive CPU holding logbuf_lock */
- printk_nmi_enter();
-
/*
* This function is only called after the system
* has panicked or is otherwise in a critical state.
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 7c9d6a2d7e90..0926e9ca4d85 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -115,7 +115,6 @@ extern void rcu_nmi_exit(void);
do { \
lockdep_off(); \
arch_nmi_enter(); \
- printk_nmi_enter(); \
BUG_ON(in_nmi() == NMI_MASK); \
__preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET); \
} while (0)
@@ -134,7 +133,6 @@ extern void rcu_nmi_exit(void);
do { \
BUG_ON(!in_nmi()); \
__preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \
- printk_nmi_exit(); \
arch_nmi_exit(); \
lockdep_on(); \
} while (0)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 2476796c1150..77f66625706e 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -149,18 +149,6 @@ static inline __printf(1, 2) __cold
void early_printk(const char *s, ...) { }
#endif
-#ifdef CONFIG_PRINTK_NMI
-extern void printk_nmi_enter(void);
-extern void printk_nmi_exit(void);
-extern void printk_nmi_direct_enter(void);
-extern void printk_nmi_direct_exit(void);
-#else
-static inline void printk_nmi_enter(void) { }
-static inline void printk_nmi_exit(void) { }
-static inline void printk_nmi_direct_enter(void) { }
-static inline void printk_nmi_direct_exit(void) { }
-#endif /* PRINTK_NMI */
-
struct dev_printk_info;
#ifdef CONFIG_PRINTK
diff --git a/init/Kconfig b/init/Kconfig
index 096e1af5c586..ea58c0d30a97 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1482,11 +1482,6 @@ config PRINTK
very difficult to diagnose system problems, saying N here is
strongly discouraged.
-config PRINTK_NMI
- def_bool y
- depends on PRINTK
- depends on HAVE_NMI
-
config BUG
bool "BUG() support" if EXPERT
default y
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 6cc35c5de890..ff890ae3ee6a 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -6,12 +6,6 @@
#ifdef CONFIG_PRINTK
-#define PRINTK_SAFE_CONTEXT_MASK 0x007ffffff
-#define PRINTK_NMI_DIRECT_CONTEXT_MASK 0x008000000
-#define PRINTK_NMI_CONTEXT_MASK 0xff0000000
-
-#define PRINTK_NMI_CONTEXT_OFFSET 0x010000000
-
__printf(4, 0)
int vprintk_store(int facility, int level,
const struct dev_printk_info *dev_info,
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 4b5df5c27334..4da1ab3332d6 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -4,12 +4,9 @@
*/
#include <linux/preempt.h>
-#include <linux/spinlock.h>
-#include <linux/debug_locks.h>
#include <linux/kdb.h>
#include <linux/smp.h>
#include <linux/cpumask.h>
-#include <linux/irq_work.h>
#include <linux/printk.h>
#include <linux/kprobes.h>
@@ -17,35 +14,6 @@
static DEFINE_PER_CPU(int, printk_context);
-#ifdef CONFIG_PRINTK_NMI
-void noinstr printk_nmi_enter(void)
-{
- this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
-}
-
-void noinstr printk_nmi_exit(void)
-{
- this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
-}
-
-/*
- * Marks a code that might produce many messages in NMI context
- * and the risk of losing them is more critical than eventual
- * reordering.
- */
-void printk_nmi_direct_enter(void)
-{
- if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
- this_cpu_or(printk_context, PRINTK_NMI_DIRECT_CONTEXT_MASK);
-}
-
-void printk_nmi_direct_exit(void)
-{
- this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);
-}
-
-#endif /* CONFIG_PRINTK_NMI */
-
/* Can be preempted by NMI. */
void __printk_safe_enter(void)
{
@@ -70,10 +38,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
* Use the main logbuf even in NMI. But avoid calling console
* drivers that might have their own locks.
*/
- if (this_cpu_read(printk_context) &
- (PRINTK_NMI_DIRECT_CONTEXT_MASK |
- PRINTK_NMI_CONTEXT_MASK |
- PRINTK_SAFE_CONTEXT_MASK)) {
+ if (this_cpu_read(printk_context) || in_nmi()) {
unsigned long flags;
int len;
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b5815a022ecc..83a3663d1dc0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9344,7 +9344,6 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
tracing_off();
local_irq_save(flags);
- printk_nmi_direct_enter();
/* Simulate the iterator */
trace_init_global_iter(&iter);
@@ -9424,7 +9423,6 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
atomic_dec(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
}
atomic_dec(&dump_running);
- printk_nmi_direct_exit();
local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(ftrace_dump);
--
2.20.1
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