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

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Message-ID: <CAHk-=whuG+5pUeUqdiW4gk0prvqu7GZSMo-6oWv5PdDC5dBr=A@mail.gmail.com>
Date:   Fri, 24 Jul 2020 10:32:51 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     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 Fri, Jul 24, 2020 at 8:24 AM Oleg Nesterov <oleg@...hat.com> wrote:
>
> not sure this makes any sense, but this looks like another user of
> trylock_page_bit_common(), see the patch below on top of 1/2.

Ok, that makes sense. Except you did it on top of the original patch
without the fix to set WQ_FLAG_WOKEN for the non-wakeup case.

And in fact, once you do it on top of that, it becomes obvious that we
can share even more code: move the WQ_FLAG_WOKEN logic _into_ the
trylock_page_bit_common() function.

Then the whole thing becomes something like the attached.

I added your reviewed-by, but maybe you should double-check my changes.

                Linus

View attachment "0001-mm-rewrite-wait_on_page_bit_common-logic.patch" of type "text/x-patch" (6751 bytes)

View attachment "0002-list-add-list_del_init_careful-to-go-with-list_empty.patch" of type "text/x-patch" (2902 bytes)