linux-kernel - Re: [PATCH] dump_stack: Avoid the livelock of the dump

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Message-ID: <CAHk-=wja287VnDKdftnQUYYe=YqX5Lz-iweA-RkcG3EGS2sD6w@mail.gmail.com>
Date:   Tue, 29 Oct 2019 16:23:33 +0100
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kevin Hao <haokexin@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] dump_stack: Avoid the livelock of the dump_lock

On Tue, Oct 29, 2019 at 3:09 PM Kevin Hao <haokexin@...il.com> wrote:
>
> Do you mean something like this?

Yeah, except I'd make it be something like

                local_irq_restore(flags);
-               cpu_relax();
+               do { cpu_relax(); } while (atomic_read(&dump_lock) != -1);
                goto retry;

instead, ie doing the cpu_relax() inside that loop.

Obviously untested.

          Linus