From: Jason Low <jason.low2@hpe.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: Waiman Long <Waiman.Long@hpe.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, 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>,
jason.low2@hp.com
Subject: Re: [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE
Date: Wed, 18 May 2016 10:21:35 -0700 [thread overview]
Message-ID: <1463592095.3369.10.camel@j-VirtualBox> (raw)
In-Reply-To: <20160518140436.GA6273@linux-uzut.site>
On Wed, 2016-05-18 at 07:04 -0700, Davidlohr Bueso wrote:
> 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.
It might be okay to leave out READ_ONCE() for reading rwsem->owner, but
couldn't we include it to at least document that we're performing a
"special" lockless read?
next prev parent reply other threads:[~2016-05-18 17:23 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
2016-05-18 17:21 ` Jason Low [this message]
2016-05-18 18:29 ` [PATCH v4 2/5] locking/rwsem: Protect all writes to owner by WRITE_ONCE 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1463592095.3369.10.camel@j-VirtualBox \
--to=jason.low2@hpe.com \
--cc=Waiman.Long@hpe.com \
--cc=dave@stgolabs.net \
--cc=david@fromorbit.com \
--cc=doug.hatch@hpe.com \
--cc=jason.low2@hp.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peter@hurleysoftware.com \
--cc=peterz@infradead.org \
--cc=scott.norton@hpe.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).