From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Feng Tang <feng.tang@intel.com>, Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>,
akpm@linux-foundation.org, bp@suse.de, keescook@chromium.org,
mm-commits@vger.kernel.org, sergey.senozhatsky@gmail.com,
stable@vger.kernel.org, tglx@linutronix.de,
Steven Rostedt <rostedt@goodmis.org>,
Sasha Levin <sashal@kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: + panic-avoid-the-extra-noise-dmesg.patch added to -mm tree
Date: Wed, 5 Dec 2018 14:29:12 +0900 [thread overview]
Message-ID: <20181205052912.GA423@jagdpanzerIV> (raw)
In-Reply-To: <20181205025728.GC503@jagdpanzerIV>
On (12/05/18 11:57), Sergey Senozhatsky wrote:
> On (12/05/18 10:47), Feng Tang wrote:
> >
> > Btw, just FYI, I just tried the sysrq (using minicom CTL + A + F + 'magic key'),
> > it works with system is running, but failed after I trigger a panic, I will
> > check more though I'm not very familiar with sysrq yet.
OK... So, apparently, what's happening is panic() calls smp_send_stop().
And smp_send_stop()->native_stop_other_cpus() on x86 disables local APIC.
So no fun anymore.
If I keep APIC enabled on panic CPU, then I have my keyboard working,
including PageUp-PageDown scrolling, sysrq handling, and so on.
I think I'm not the only one who'd want scrollback to work after panic
(yes, fremebuffer for debugging).
Andi Kleen [1] wrote (Cc-ed):
: Oops/warnings are getting longer and longer, often scrolling away
: from the screen, and if the kernel crashes backscroll does not work
: anymore, so precious information is lost.
PeterZ,
for those folks who sometimes have to use framebuffer for debugging
(just a trivial "let me scrollback and see the panic backtrace") and
not always have access to serial console, can we have local APIC
enabled on the panic_cpu? Or is it a terrible thing to ask for?
[1] https://lore.kernel.org/lkml/878tcvt592.fsf@linux.intel.com/T/#u
-ss
next prev parent reply other threads:[~2018-12-05 5:29 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 7:15 + panic-avoid-the-extra-noise-dmesg.patch added to -mm tree akpm
2018-12-04 10:10 ` Sergey Senozhatsky
2018-12-04 10:20 ` Petr Mladek
2018-12-04 15:49 ` Feng Tang
2018-12-04 16:01 ` Petr Mladek
2018-12-05 1:53 ` Feng Tang
2018-12-05 2:50 ` Sergey Senozhatsky
2018-12-05 3:05 ` Sergey Senozhatsky
2018-12-05 3:27 ` Feng Tang
2018-12-05 2:26 ` Sergey Senozhatsky
2018-12-05 2:47 ` Feng Tang
2018-12-05 2:57 ` Sergey Senozhatsky
2018-12-05 5:29 ` Sergey Senozhatsky [this message]
2018-12-05 8:00 ` Sergey Senozhatsky
2018-12-05 15:46 ` Feng Tang
2018-12-06 3:58 ` Feng Tang
2018-12-07 9:50 ` Sergey Senozhatsky
2018-12-10 9:45 ` Feng Tang
2018-12-10 15:57 ` Petr Mladek
2018-12-11 8:07 ` Sergey Senozhatsky
2018-12-11 8:22 ` Petr Mladek
2018-12-11 8:26 ` Sergey Senozhatsky
2018-12-11 8:32 ` Feng Tang
2018-12-11 9:08 ` Sergey Senozhatsky
2018-12-11 8:00 ` Sergey Senozhatsky
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