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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: hannes@cmpxchg.org
Cc: akpm@linux-foundation.org, alan@llwyncelyn.cymru, hch@lst.de,
	mhocko@suse.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is killed"
Date: Thu, 5 Oct 2017 06:42:38 +0900	[thread overview]
Message-ID: <201710050642.JJI34818.QFSHJOMOtFOLFV@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20171004210027.GA2973@cmpxchg.org>

Johannes Weiner wrote:
> On Thu, Oct 05, 2017 at 05:49:43AM +0900, Tetsuo Handa wrote:
> > On 2017/10/05 3:59, Johannes Weiner wrote:
> > > But the justification to make that vmalloc() call fail like this isn't
> > > convincing, either. The patch mentions an OOM victim exhausting the
> > > memory reserves and thus deadlocking the machine. But the OOM killer
> > > is only one, improbable source of fatal signals. It doesn't make sense
> > > to fail allocations preemptively with plenty of memory in most cases.
> > 
> > By the time the current thread reaches do_exit(), fatal_signal_pending(current)
> > should become false. As far as I can guess, the source of fatal signal will be
> > tty_signal_session_leader(tty, exit_session) which is called just before
> > tty_ldisc_hangup(tty, cons_filp != NULL) rather than the OOM killer. I don't
> > know whether it is possible to make fatal_signal_pending(current) true inside
> > do_exit() though...
> 
> It's definitely not the OOM killer, the memory situation looks fine
> when this happens. I didn't look closer where the signal comes from.
> 

Then, we could check tsk_is_oom_victim() instead of fatal_signal_pending().

> That said, we trigger this issue fairly easily. We tested the revert
> over night on a couple thousand machines, and it fixed the issue
> (whereas the control group still saw the crashes).
> 

WARNING: multiple messages have this Message-ID (diff)
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: hannes@cmpxchg.org
Cc: akpm@linux-foundation.org, alan@llwyncelyn.cymru, hch@lst.de,
	mhocko@suse.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is killed"
Date: Thu, 5 Oct 2017 06:42:38 +0900	[thread overview]
Message-ID: <201710050642.JJI34818.QFSHJOMOtFOLFV@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <20171004210027.GA2973@cmpxchg.org>

Johannes Weiner wrote:
> On Thu, Oct 05, 2017 at 05:49:43AM +0900, Tetsuo Handa wrote:
> > On 2017/10/05 3:59, Johannes Weiner wrote:
> > > But the justification to make that vmalloc() call fail like this isn't
> > > convincing, either. The patch mentions an OOM victim exhausting the
> > > memory reserves and thus deadlocking the machine. But the OOM killer
> > > is only one, improbable source of fatal signals. It doesn't make sense
> > > to fail allocations preemptively with plenty of memory in most cases.
> > 
> > By the time the current thread reaches do_exit(), fatal_signal_pending(current)
> > should become false. As far as I can guess, the source of fatal signal will be
> > tty_signal_session_leader(tty, exit_session) which is called just before
> > tty_ldisc_hangup(tty, cons_filp != NULL) rather than the OOM killer. I don't
> > know whether it is possible to make fatal_signal_pending(current) true inside
> > do_exit() though...
> 
> It's definitely not the OOM killer, the memory situation looks fine
> when this happens. I didn't look closer where the signal comes from.
> 

Then, we could check tsk_is_oom_victim() instead of fatal_signal_pending().

> That said, we trigger this issue fairly easily. We tested the revert
> over night on a couple thousand machines, and it fixed the issue
> (whereas the control group still saw the crashes).
> 

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  reply	other threads:[~2017-10-04 21:42 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-03 22:55 tty crash due to auto-failing vmalloc Johannes Weiner
2017-10-03 22:55 ` Johannes Weiner
2017-10-03 23:51 ` Alan Cox
2017-10-03 23:51   ` Alan Cox
2017-10-04  8:33 ` Michal Hocko
2017-10-04  8:33   ` Michal Hocko
2017-10-04 18:58 ` Johannes Weiner
2017-10-04 18:58   ` Johannes Weiner
2017-10-04 18:59   ` [PATCH 1/2] Revert "vmalloc: back off when the current task is killed" Johannes Weiner
2017-10-04 18:59     ` Johannes Weiner
2017-10-04 20:49     ` Tetsuo Handa
2017-10-04 20:49       ` Tetsuo Handa
2017-10-04 21:00       ` Johannes Weiner
2017-10-04 21:00         ` Johannes Weiner
2017-10-04 21:42         ` Tetsuo Handa [this message]
2017-10-04 21:42           ` Tetsuo Handa
2017-10-04 23:21           ` Johannes Weiner
2017-10-04 23:21             ` Johannes Weiner
2017-10-04 22:32     ` Andrew Morton
2017-10-04 22:32       ` Andrew Morton
2017-10-04 23:18       ` Johannes Weiner
2017-10-04 23:18         ` Johannes Weiner
2017-10-05  7:57         ` Michal Hocko
2017-10-05  7:57           ` Michal Hocko
2017-10-05 10:36           ` Tetsuo Handa
2017-10-05 10:36             ` Tetsuo Handa
2017-10-05 10:49             ` Michal Hocko
2017-10-05 10:49               ` Michal Hocko
2017-10-07  2:21             ` Tetsuo Handa
2017-10-07  2:21               ` Tetsuo Handa
2017-10-07  2:51               ` Johannes Weiner
2017-10-07  2:51                 ` Johannes Weiner
2017-10-07  4:05                 ` Tetsuo Handa
2017-10-07  4:05                   ` Tetsuo Handa
2017-10-07  7:59                   ` Michal Hocko
2017-10-07  7:59                     ` Michal Hocko
2017-10-07  9:57                     ` Tetsuo Handa
2017-10-07  9:57                       ` Tetsuo Handa
2017-10-05  6:49     ` Vlastimil Babka
2017-10-05  6:49       ` Vlastimil Babka
2017-10-05  7:54     ` Michal Hocko
2017-10-05  7:54       ` Michal Hocko
2017-10-04 18:59   ` [PATCH 2/2] tty: fall back to N_NULL if switching to N_TTY fails during hangup Johannes Weiner
2017-10-04 18:59     ` Johannes Weiner

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