Re: [PATCH v6] panic: Avoid the extra noise dmesg
From: Petr Mladek
Date: Fri Mar 01 2019 - 05:06:41 EST
On Fri 2019-03-01 16:49:46, Feng Tang wrote:
> When kernel panic happens, it will first print the panic call stack,
> then the ending msg like:
> [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
> [ 35.749975] ------------[ cut here ]------------
> The above message are very useful for debugging.
> But if system is configured to not reboot on panic, say the "panic_timeout"
> parameter equals 0, it will likely print out many noisy message like
> WARN() call stack for each and every CPU except the panic one, messages
> like below:
> WARNING: CPU: 1 PID: 280 at kernel/sched/core.c:1198 set_task_cpu+0x183/0x190
> Call Trace:
> For people working in console mode, the screen will first show the panic
> call stack, but immediately overridden by these noisy extra messages, which
> makes debugging much more difficult, as the original context gets lost on
> Also these noisy messages will confuse some users, as I have seen many bug
> reporters posted the noisy message into bugzilla, instead of the real panic
> call stack and context.
> Adding a flag "suppress_printk" which gets set in panic() to avoid those
> noisy messages, without changing current kernel behavior that both panic
> blinking and sysrq magic key can work as is, suggested by Petr Mladek.
> To verify this, make sure kernel is not configured to reboot on panic and
> in console
> # echo c > /proc/sysrq-trigger
> to see if console only prints out the panic call stack.
> Suggested-by: Petr Mladek <pmladek@xxxxxxxx>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
The patch looks fine to me:
Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>