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Date: Sat, 1 Oct 2016 08:47:31 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Waiman Long <Waiman.Long@hpe.com>
cc: Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
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Subject: Re: [PATCH v3 07/13] futex: Throughput-optimized (TP) futexes
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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