The patch titled
Subject: printk/nmi: restore printk_func in nmi_panic
has been added to the -mm tree. Its filename is
printk-nmi-generic-solution-for-safe-printk-in-nmi-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/printk-nmi-generic-solution-for-safe-printk-in-nmi-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/printk-nmi-generic-solution-for-safe-printk-in-nmi-fix.patch
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------------------------------------------------------
From: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Subject: printk/nmi: restore printk_func in nmi_panic
When watchdog detects a hardlockup and calls nmi_panic() `printk_func'
must be restored via printk_nmi_exit() call, so panic() will be able
to flush nmi buf and show backtrace and panic message. We also better
explicitly ask nmi to printk_nmi_flush() in console_flush_on_panic(),
because it may be too late to rely on irq work.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 6 ++++--
kernel/printk/printk.c | 1 +
2 files changed, 5 insertions(+), 2 deletions(-)
diff -puN include/linux/kernel.h~printk-nmi-generic-solution-for-safe-printk-in-nmi-fix include/linux/kernel.h
--- a/include/linux/kernel.h~printk-nmi-generic-solution-for-safe-printk-in-nmi-fix
+++ a/include/linux/kernel.h
@@ -467,10 +467,12 @@ do { \
cpu = raw_smp_processor_id(); \
old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu); \
\
- if (old_cpu == PANIC_CPU_INVALID) \
+ if (old_cpu == PANIC_CPU_INVALID) { \
+ printk_nmi_exit(); \
panic(fmt, ##__VA_ARGS__); \
- else if (old_cpu != cpu) \
+ } else if (old_cpu != cpu) { \
nmi_panic_self_stop(regs); \
+ } \
} while (0)
/*
diff -puN kernel/printk/printk.c~printk-nmi-generic-solution-for-safe-printk-in-nmi-fix kernel/printk/printk.c
--- a/kernel/printk/printk.c~printk-nmi-generic-solution-for-safe-printk-in-nmi-fix
+++ a/kernel/printk/printk.c
@@ -2392,6 +2392,7 @@ void console_flush_on_panic(void)
*/
console_trylock();
console_may_schedule = 0;
+ printk_nmi_flush();
console_unlock();
}
_
Patches currently in -mm which might be from sergey.senozhatsky.work@xxxxxxxxx are
printk-nmi-generic-solution-for-safe-printk-in-nmi-fix.patch
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