Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Date:   Fri, 14 Sep 2018 21:22:17 +0900
To:     Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Alexander Potapenko <glider@google.com>,
        Dmitriy Vyukov <dvyukov@google.com>,
        kbuild test robot <fengguang.wu@intel.com>,
        syzkaller <syzkaller@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] printk: inject caller information into the body of
 message
Message-ID: <20180914122217.GA518@tigerII.localdomain>
References: <CAG_fn=XuZo5yrZzVizP26iV6eFfJtAHUs4NsDFXFyvnaJkdSQw@mail.gmail.com>
 <20180912065307.GA606@jagdpanzerIV>
 <20180912120548.4280f04a@vmware.local.home>
 <20180913071204.GA604@jagdpanzerIV>
 <20180913122625.6ieyexpcmlc5z2it@pathway.suse.cz>
 <20180913142802.GB517@tigerII.localdomain>
 <20180914065728.GA515@jagdpanzerIV>
 <49d22738-17ad-410a-be0a-d27d76ba9f37@i-love.sakura.ne.jp>
 <20180914115028.GB20572@tigerII.localdomain>
 <e855cbef-03ff-b4ac-3e06-d2f2f48cfb1f@i-love.sakura.ne.jp>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <e855cbef-03ff-b4ac-3e06-d2f2f48cfb1f@i-love.sakura.ne.jp>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On (09/14/18 21:03), Tetsuo Handa wrote:
> > 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.

... by "OOM people" I meant "MM people".
"MM people" is a subset of "OOM people".

OK, so I didn't notice the "static" part of the `oom_print_buf'.
I need some rest, I guess.

The "SMP-safe" comment becomes a bit tricky when pr_line is used with a
static buffer. Either we need to require synchronization - umm... and
document it - or to provide some means of synchronization in pr_line().
Let's think what pr_line API should do about it.

Any thoughts?

	-ss