From: John Ogness <john.ogness@linutronix.de>
To: Sergey Senozhatsky <senozhatsky@chromium.org>,
Stephen Brennan <stephen.s.brennan@oracle.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>,
Petr Mladek <pmladek@suse.com>,
Steven Rostedt <rostedt@goodmis.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] printk: disable optimistic spin during panic
Date: Thu, 27 Jan 2022 10:15:05 +0106 [thread overview]
Message-ID: <87ilu5pmtq.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <YfJFjHdg/khNXiRd@google.com>
On 2022-01-27, Sergey Senozhatsky <senozhatsky@chromium.org> wrote:
> Right. So I also thought about placing panic_in_progress() somewhere in
> console_trylock() and make it fail for anything that is not a panic
> CPU.
I think this is a good idea and console_trylock() is the correct place
for that.
> Back in the days we also had this idea of "detaching" non-panic CPUs from
> printk() by overwriting their printk function pointers.
We need to keep in mind that printk() is no longer the problem. The
records are stored locklessly. The problem is the
console_trylock()/console_unlock() within vprintk_emit(). IMHO adding a
panic check in console_trylock() should solve that race sufficiently.
John
next prev parent reply other threads:[~2022-01-27 9:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-21 19:02 [PATCH 0/4] printk: reduce deadlocks " Stephen Brennan
2022-01-21 19:02 ` [PATCH 1/4] panic: Add panic_in_progress helper Stephen Brennan
2022-01-25 11:48 ` Petr Mladek
2022-01-26 17:37 ` Stephen Brennan
2022-01-21 19:02 ` [PATCH 2/4] printk: disable optimistic spin during panic Stephen Brennan
2022-01-25 12:42 ` Petr Mladek
2022-01-26 9:18 ` Sergey Senozhatsky
2022-01-26 9:45 ` John Ogness
2022-01-26 10:06 ` Sergey Senozhatsky
2022-01-26 18:15 ` Stephen Brennan
2022-01-27 7:11 ` Sergey Senozhatsky
2022-01-27 9:09 ` John Ogness [this message]
2022-01-27 11:38 ` Petr Mladek
2022-01-27 12:43 ` John Ogness
2022-01-27 14:25 ` Petr Mladek
2022-01-21 19:02 ` [PATCH 3/4] printk: Avoid livelock with heavy printk " Stephen Brennan
2022-01-25 14:25 ` Petr Mladek
2022-01-21 19:02 ` [PATCH 4/4] printk: Drop console_sem " Stephen Brennan
2022-01-24 16:12 ` John Ogness
2022-01-24 16:26 ` John Ogness
2022-01-25 15:04 ` Petr Mladek
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