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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
	linux-kernel@vger.kernel.org, "4 . 13+" <stable@vger.kernel.org>
Subject: Re: [PATCH] printk/nmi: Prevent deadlock when serializing NMI backtraces
Date: Fri, 18 May 2018 15:38:20 +0900	[thread overview]
Message-ID: <20180518063820.GA1504@jagdpanzerIV> (raw)
In-Reply-To: <20180518020705.GB1160@jagdpanzerIV>

On (05/18/18 11:07), Sergey Senozhatsky wrote:
> 
> if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) ||
> 	raw_spin_is_locked(&logbuf_lock)
> 
> just to check per-CPU `printk_context' first and only afterwards
> access the global `logbuf_lock'. printk_nmi_enter() happens on
> every CPU, so maybe we can avoid some overhead by checking the
> local per-CPU data first.

Nah, may be it won't. This, probably, would have been the case if we
had continue to call console drivers from printk_safe section [at least].
CPUs don't spend that much time in printk_safe sections.

	-ss

  reply	other threads:[~2018-05-18  6:38 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-17 14:39 [PATCH] printk/nmi: Prevent deadlock when serializing NMI backtraces Petr Mladek
2018-05-18  2:07 ` Sergey Senozhatsky
2018-05-18  6:38   ` Sergey Senozhatsky [this message]
2018-05-18  8:10     ` Petr Mladek
2018-05-22 21:43 ` Steven Rostedt
2018-05-23  2:01   ` Sergey Senozhatsky
2018-05-28 12:27     ` Petr Mladek
2018-06-05 12:47 ` Petr Mladek
2018-06-06  5:10   ` Sergey Senozhatsky
2018-06-06 10:33     ` Sergey Senozhatsky
2018-06-08 10:48       ` Petr Mladek
2018-06-18  6:37         ` Sergey Senozhatsky
2018-06-18  9:39           ` Petr Mladek
2018-06-18 10:07             ` Sergey Senozhatsky
2018-06-19  7:52               ` Petr Mladek
2018-06-19  8:27                 ` Sergey Senozhatsky
2018-06-19 13:23                   ` Steven Rostedt
2018-06-20  1:58                     ` Sergey Senozhatsky
2018-06-20  2:32                       ` Steven Rostedt
2018-06-20  4:17                         ` Sergey Senozhatsky
2018-06-06 11:15     ` Petr Mladek
2018-06-07  5:40       ` Sergey Senozhatsky

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