linux-kernel - Re: [PATCH] printk: inject caller information into the body of message

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Message-ID: <20181001023721.GA6409@jagdpanzerIV>
Date:   Mon, 1 Oct 2018 11:37:21 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitriy Vyukov <dvyukov@...gle.com>,
        kbuild test robot <fengguang.wu@...el.com>,
        syzkaller <syzkaller@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] printk: inject caller information into the body of
 message

On (09/29/18 20:15), Tetsuo Handa wrote:
> 
> Because there is no guarantee that memory information is dumped under the
> oom_lock mutex. The oom_lock is held when calling out_of_memory(), and it
> cannot be held when reporting GFP_ATOMIC memory allocation failures.

IOW, static pr_line buffer needs additional synchronization for OOM. Correct?

If we are about to have a list of printk buffers then we probably can
define a list of NR_CPUS cont buffers. And we probably can reuse the
existing struct cont for buffered printk, having 2 different struct-s
for the same thing - struct cont and struct printk_buffer - is not very
cool.

> But I don't want line buffered printk() API to truncate upon out of
> space for line buffered printk() API.

All printk()-s are limited by LOG_LINE_MAX. Buffered printk() is not
special.

	-ss