linux-kernel - Re: [RFC PATCH] mm: silence soft lockups from unlock

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Message-ID: <alpine.LSU.2.11.2007231549540.1016@eggly.anvils>
Date:   Thu, 23 Jul 2020 16:11:27 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
cc:     Oleg Nesterov <oleg@...hat.com>, Hugh Dickins <hughd@...gle.com>,
        Michal Hocko <mhocko@...nel.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [RFC PATCH] mm: silence soft lockups from unlock_page

On Thu, 23 Jul 2020, Linus Torvalds wrote:
> 
> I'll send a new version after I actually test it.

I'll give it a try when you're happy with it. I did try yesterday's
with my swapping loads on home machines (3 of 4 survived 16 hours),
and with some google stresstests on work machines (0 of 10 survived).

I've not spent long analyzing the crashes, all of them in or below
__wake_up_common() called from __wake_up_locked_key_bookmark():
sometimes gets to run the curr->func() and crashes on something
inside there (often list_del's lib/list_debug.c:53!), sometimes
cannot get that far. Looks like the wait queue entries on the list
were not entirely safe with that patch.

Hugh