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printk/panic: Allow cpu backtraces to be written into ringbuffer during panic

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commit 779dbc2e78 ("printk: Avoid non-panic CPUs writing
to ringbuffer") disabled non-panic CPUs to further write messages to
ringbuffer after panicked.

Since the commit, non-panicked CPU's are not allowed to write to
ring buffer after panicked and CPU backtrace which is triggered
after panicked to sample non-panicked CPUs' backtrace no longer
serves its function as it has nothing to print.

Fix the issue by allowing non-panicked CPUs to write into ringbuffer
while CPU backtrace is in flight.

Fixes: 779dbc2e78 ("printk: Avoid non-panic CPUs writing to ringbuffer")
Signed-off-by: Ryo Takakura <takakura@valinux.co.jp>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240812072703.339690-1-takakura@valinux.co.jp
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
Ryo Takakura
2024-08-12 16:27:03 +09:00
committed by Petr Mladek
parent 8bf100092d
commit bcc954c6ca
3 changed files with 9 additions and 2 deletions
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kernel/printk/printk.c
+1 -1
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@@ -2316,7 +2316,7 @@ asmlinkage int vprintk_emit(int facility, int level,
* non-panic CPUs are generating any messages, they will be
* silently dropped.
*/
if (other_cpu_in_panic())
if (other_cpu_in_panic() && !panic_triggering_all_cpu_backtrace)
return 0;
if (level == LOGLEVEL_SCHED) {