From: Andrew Morton <akpm@linux-foundation.org>
To: Feng Tang <feng.tang@intel.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Petr Mladek <pmladek@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@suse.de>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Andi Kleen <ak@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>, Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH v5] panic: Avoid the extra noise dmesg
Date: Thu, 28 Feb 2019 12:00:14 -0800 [thread overview]
Message-ID: <20190228120014.19c0ab9227809341c1d5acc6@linux-foundation.org> (raw)
In-Reply-To: <20190222060959.pe3u4yvcjw6yj347@shbuild888>
On Fri, 22 Feb 2019 14:09:59 +0800 Feng Tang <feng.tang@intel.com> 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:
> <IRQ>
> try_to_wake_up
> default_wake_function
> autoremove_wake_function
> __wake_up_common
> __wake_up_common_lock
> __wake_up
> wake_up_klogd_work_func
> irq_work_run_list
> irq_work_tick
> update_process_times
> tick_sched_timer
> __hrtimer_run_queues
> hrtimer_interrupt
> smp_apic_timer_interrupt
> apic_timer_interrupt
It's a fairly ugly-looking patch but I am inclined to agree.
The panicing CPU is spinning and blinking a LED and all CPUs have
interrupts enabled and the system is known to be in a messed up state.
All sorts of kernel code could emit all sorts of output in such
circumstances. So a global printk-killing knob seems appropriate.
Thoughts:
- why do the suppression in vprintk_emit()? Doing it right at entry
to printk() seems cleaner, more explicit?
- Other code sites may wish to suppress all printks. Perhaps
`panic_suppress_printk' should just be called `suppress_printk'?
next prev parent reply other threads:[~2019-02-28 20:00 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-22 6:00 [PATCH v5] panic: Avoid the extra noise dmesg Feng Tang
2019-02-22 6:09 ` Feng Tang
2019-02-28 20:00 ` Andrew Morton [this message]
2019-03-01 4:11 ` Feng Tang
2019-03-01 8:54 ` Petr Mladek
2019-03-01 19:29 ` Steven Rostedt
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