linux-kernel - Re: [RFC PATCH for 4.18 00/14] Restartable Sequences

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Message-ID: <20180502124253.145253cb@gandalf.local.home>
Date:   Wed, 2 May 2018 12:42:53 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Daniel Colascione <dancol@...gle.com>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        boqun.feng@...il.com, luto@...capital.net, davejwatson@...com,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        Paul Turner <pjt@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux@....linux.org.uk, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, Andrew Hunter <ahh@...gle.com>, andi@...stfloor.org,
        cl@...ux.com, bmaurer@...com, josh@...htriplett.org,
        torvalds@...ux-foundation.org, catalin.marinas@....com,
        will.deacon@....com,
        Michael Kerrisk-manpages <mtk.manpages@...il.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [RFC PATCH for 4.18 00/14] Restartable Sequences

On Wed, 02 May 2018 16:07:48 +0000
Daniel Colascione <dancol@...gle.com> wrote:

> Why couldn't we take a page fault just before schedule? The reason we can't
> take a page fault in atomic context is that doing so might call schedule.
> Here, we're about to call schedule _anyway_, so what harm does it do to
> call something that might call schedule? If we schedule via that call, we
> can skip the manual schedule we were going to perform.

Another issue is slowing down something that is considered a fast path.

-- Steve