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Message-ID: <alpine.DEB.2.20.1610010844490.5067@nanos>
Date: Sat, 1 Oct 2016 08:47:31 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: Waiman Long <Waiman.Long@....com>
cc: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Davidlohr Bueso <dave@...olabs.net>,
Mike Galbraith <umgwanakikbuti@...il.com>,
Jason Low <jason.low2@....com>,
Scott J Norton <scott.norton@....com>,
Douglas Hatch <doug.hatch@....com>
Subject: Re: [PATCH v3 07/13] futex: Throughput-optimized (TP) futexes
On Fri, 30 Sep 2016, Waiman Long wrote:
> + WRITE_ONCE(state->owner, current);
> + preempt_disable();
> + for (;;) {
> + ret = futex_trylock(uaddr, vpid, &uval, true);
Did you actually read what I said? You CANNOT access userspace in a preempt
disabled region without disabling pagefaults and handle the resulting
wreckage yourself.
End of review.
tglx
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