From: Davidlohr Bueso <dave@stgolabs.net>
To: Waiman Long <Waiman.Long@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Jason Low <jason.low2@hp.com>,
Dave Chinner <david@fromorbit.com>,
Peter Hurley <peter@hurleysoftware.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>
Subject: Re: [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE()
Date: Wed, 18 May 2016 07:04:36 -0700 [thread overview]
Message-ID: <20160518140436.GA6273@linux-uzut.site> (raw)
In-Reply-To: <1463534783-38814-3-git-send-email-Waiman.Long@hpe.com>
On Tue, 17 May 2016, Waiman Long wrote:
>Without using WRITE_ONCE(), the compiler can potentially break a
>write into multiple smaller ones (store tearing). So a read from the
>same data by another task concurrently may return a partial result.
>This can result in a kernel crash if the data is a memory address
>that is being dereferenced.
>
>This patch changes all write to rwsem->owner to use WRITE_ONCE()
>to make sure that store tearing will not happen. READ_ONCE() may
>not be needed for rwsem->owner as long as the value is only used for
>comparison and not dereferencing.
>
>Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Yes, ->owner can obviously be handled locklessly during optimistic
spinning.
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
next prev parent reply other threads:[~2016-05-18 14:04 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-18 1:26 [PATCH v4 0/5] [PATCH v3 0/4] locking/rwsem: Add reader-owned state to the owner field Waiman Long
2016-05-18 1:26 ` [PATCH v4 1/5] " Waiman Long
2016-06-06 17:18 ` Davidlohr Bueso
2016-06-06 20:03 ` Waiman Long
2016-06-06 21:02 ` Peter Zijlstra
2016-06-06 21:49 ` Waiman Long
2016-06-08 14:25 ` [tip:locking/core] " tip-bot for Waiman Long
2016-05-18 1:26 ` [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE() Waiman Long
2016-05-18 14:04 ` Davidlohr Bueso [this message]
2016-05-18 17:21 ` [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE Jason Low
2016-05-18 18:29 ` Waiman Long
2016-05-18 19:58 ` Jason Low
2016-05-19 22:21 ` Jason Low
2016-05-20 20:26 ` Waiman Long
2016-05-21 16:04 ` Peter Hurley
2016-05-22 10:42 ` Peter Zijlstra
2016-05-23 18:46 ` Jason Low
2016-05-23 19:44 ` Davidlohr Bueso
2016-05-23 20:15 ` Paul E. McKenney
2016-05-23 21:04 ` Davidlohr Bueso
2016-05-25 1:25 ` Waiman Long
2016-05-18 17:23 ` [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE() Jason Low
2016-06-08 14:25 ` [tip:locking/core] " tip-bot for Waiman Long
2016-05-18 1:26 ` [PATCH v4 3/5] locking/rwsem: Don't wake up one's own task Waiman Long
2016-05-18 10:30 ` Peter Zijlstra
2016-05-18 16:04 ` Waiman Long
2016-05-18 1:26 ` [PATCH v4 4/5] locking/rwsem: Improve reader wakeup code Waiman Long
2016-06-08 14:25 ` [tip:locking/core] " tip-bot for Waiman Long
2016-05-18 1:26 ` [PATCH v4 5/5] locking/rwsem: Streamline the rwsem_optimistic_spin() code Waiman Long
2016-06-08 14:26 ` [tip:locking/core] " tip-bot for Waiman Long
2016-05-18 10:52 ` [PATCH v4 0/5] [PATCH v3 0/4] locking/rwsem: Add reader-owned state to the owner field Peter Zijlstra
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