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

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Message-ID: <e855cbef-03ff-b4ac-3e06-d2f2f48cfb1f@i-love.sakura.ne.jp>
Date:   Fri, 14 Sep 2018 21:03:20 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     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 2018/09/14 20:50, Sergey Senozhatsky wrote:
>>> +#define DEFINE_PR_LINE_BUF(lev, name, buf, sz)			\
>>> +	struct pr_line	name = {				\
>>> +		.sb	= __SEQ_BUF_INITIALIZER(buf, (sz)),	\
>>> +		.level	= lev,					\
>>> +	}
>>> +
>>
>> I would use this one for the OOM killer. 80 bytes is too short.
> 
> 80 bytes is quite short for OOM, agreed.
> 
>>   static char oom_print_buf[1024];
>>   DEFINE_PR_LINE_BUF(level, oom_print_buf);
> 
> Do I get it right that you suggest to drop the "size" param?

No. I just forgot to add params. ;-)

> Do OOM people agree on 1024 bytes stack usage?

I won't allocate oom_print_buf on the stack. Since its usage is serialized
by oom_lock mutex, we don't need to allocate from stack. Since memory
allocation request might happen when stack is already tight, we should not
try to allocate much from stack.