From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id E4C3C6B0006 for ; Mon, 22 Oct 2018 20:47:32 -0400 (EDT) Received: by mail-pg1-f200.google.com with SMTP id b7-v6so30800593pgt.10 for ; Mon, 22 Oct 2018 17:47:32 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id b66-v6sor18256907pfm.43.2018.10.22.17.47.31 for (Google Transport Security); Mon, 22 Oct 2018 17:47:31 -0700 (PDT) Date: Tue, 23 Oct 2018 09:47:26 +0900 From: Sergey Senozhatsky Subject: Re: [PATCH v3] mm: memcontrol: Don't flood OOM messages with no eligible task. Message-ID: <20181023004726.GA4612@jagdpanzerIV> References: <201810180246.w9I2koi3011358@www262.sakura.ne.jp> <20181018042739.GA650@jagdpanzerIV> <201810180526.w9I5QvVn032670@www262.sakura.ne.jp> <20181018061018.GB650@jagdpanzerIV> <20181018075611.GY18839@dhcp22.suse.cz> <20181018081352.GA438@jagdpanzerIV> <2c2b2820-e6f8-76c8-c431-18f60845b3ab@i-love.sakura.ne.jp> <20181018235427.GA877@jagdpanzerIV> <5d472476-7852-f97b-9412-63536dffaa0e@i-love.sakura.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5d472476-7852-f97b-9412-63536dffaa0e@i-love.sakura.ne.jp> Sender: owner-linux-mm@kvack.org List-ID: To: Tetsuo Handa Cc: Sergey Senozhatsky , Michal Hocko , Johannes Weiner , linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, guro@fb.com, kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org, rientjes@google.com, yang.s@alibaba-inc.com, Andrew Morton , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , syzbot , Calvin Owens On (10/19/18 19:35), Tetsuo Handa wrote: > > > > OK, that's a fair point. There was a patch from FB, which would allow us > > to set a log_level on per-console basis. So the noise goes to heav^W net > > console; only critical stuff goes to the serial console (if I recall it > > correctly). I'm not sure what happened to that patch, it was a while ago. > > I'll try to find that out. > > Per a console loglevel setting would help for several environments. > But syzbot environment cannot count on netconsole. We can't expect that > unlimited printk() will become safe. This target is moving too fast :) RCU stall -> user interaction -> syzbot I talked to Calvin Owens (who's working on the per-console loglevel patch set; CC-ed) and Calvin said that "It's in-progress". So we probably will have this functionality one day. That's all we can do from printk side wrt user-interaction problem. > > The problem you are talking about is not MM specific. You can have a > > faulty SCSI device, corrupted FS, and so and on. > > "a faulty SCSI device, corrupted FS, and so and on" are reporting problems > which will complete a request. They can use (and are using) ratelimit, > aren't they? Looking at scsi_request_fn(), the answer is probably "sure they can; but no, they aren't". In majority of cases the reason we replace printk with printk_ratelimit is because someone reports a stall or a lockup. Otherwise, people use printk(), which is absolutely fine. -ss