linux-kernel - Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is killed"

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Date:   Thu, 5 Oct 2017 05:49:43 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Alan Cox <alan@...yncelyn.cymru>, Christoph Hellwig <hch@....de>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 1/2] Revert "vmalloc: back off when the current task is
 killed"

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...