linux-kernel - Re: [PATCH 1/2] sched/wait: Break up long wake list walk

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Message-ID: <CA+55aFw84Cu0VZdR_Rj6b03hMYBFgt9BCnSEx+OLXDsp4dDO=g@mail.gmail.com>
Date:   Tue, 15 Aug 2017 15:57:32 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...e.hu>, Kan Liang <kan.liang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] sched/wait: Break up long wake list walk

On Tue, Aug 15, 2017 at 3:56 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Except they really don't actually work for this case, exactly because
> they also simplify away "minor" details like exclusive vs
> non-exclusive etc.
>
> The page wait-queue very much has a mix of "wake all" and "wake one" semantics.

Oh, and the page wait-queue really needs that key argument too, which
is another thing that swait queue code got rid of in the name of
simplicity.

So no. The swait code is absolutely _entirely_ the wrong thing to use.

                 Linus