From: Thomas Gleixner <tglx@linutronix.de>
To: Waiman Long <Waiman.Long@hpe.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Jonathan Corbet <corbet@lwn.net>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Jason Low <jason.low2@hpe.com>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [PATCH v3 07/13] futex: Throughput-optimized (TP) futexes
Date: Sat, 1 Oct 2016 08:47:31 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1610010844490.5067@nanos> (raw)
In-Reply-To: <1475270782-51720-8-git-send-email-Waiman.Long@hpe.com>
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
next prev parent reply other threads:[~2016-10-01 6:50 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-30 21:26 [PATCH v3 00/13] futex: Introducing throughput-optimized futexes Waiman Long
2016-09-30 21:26 ` [PATCH v3 01/13] futex: Consolidate duplicated timer setup code Waiman Long
2016-09-30 21:26 ` [PATCH v3 02/13] futex: Rename futex_pi_state to futex_state Waiman Long
2016-09-30 21:26 ` [PATCH v3 03/13] futex: Add helpers to get & cmpxchg futex value without lock Waiman Long
2016-09-30 21:26 ` [PATCH v3 04/13] futex: Consolidate pure pi_state_list add & delete codes to helpers Waiman Long
2016-09-30 21:26 ` [PATCH v3 05/13] futex: Add a new futex type field into futex_state Waiman Long
2016-09-30 21:26 ` [PATCH v3 06/13] futex: Allow direct attachment of futex_state objects to hash bucket Waiman Long
2016-09-30 21:26 ` [PATCH v3 07/13] futex: Throughput-optimized (TP) futexes Waiman Long
2016-10-01 6:47 ` Thomas Gleixner [this message]
2016-10-02 1:12 ` Waiman Long
2016-09-30 21:26 ` [PATCH v3 08/13] futex: Enable robust handling of TP futexes Waiman Long
2016-09-30 21:26 ` [PATCH v3 09/13] futex: Implement lock handoff for TP futexes to prevent lock starvation Waiman Long
2016-09-30 21:26 ` [PATCH v3 10/13] futex: Inform FUTEX_LOCK callers on how the lock is acquired Waiman Long
2016-09-30 21:26 ` [PATCH v3 11/13] futex: Add timeout support to TP futexes Waiman Long
2016-09-30 21:26 ` [PATCH v3 12/13] futex, doc: TP futexes document Waiman Long
2016-09-30 21:26 ` [PATCH v3 13/13] perf bench: New microbenchmark for userspace mutex performance Waiman Long
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