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From: Davidlohr Bueso <dave@stgolabs.net>
To: Andrea Parri <parri.andrea@gmail.com>
Cc: Prateek Sood <prsood@codeaurora.org>,
	mingo@kernel.org, longman@redhat.com, peterz@infradead.org,
	linux-kernel@vger.kernel.org, sramana@codeaurora.org
Subject: Re: [PATCH] rwsem: fix missed wakeup due to reordering of load
Date: Wed, 27 Sep 2017 14:20:12 -0700
Message-ID: <20170927212012.GA26599@linux-80c1.suse> (raw)
In-Reply-To: <20170920211727.GA26082@andrea>

On Wed, 20 Sep 2017, Andrea Parri wrote:

>> Instead, how about just removing the release from atomic_long_sub_return_release()
>> such that the osq load is not hoisted over the atomic compound (along with Peter's
>> comment):
>
>This solution will actually enforce a stronger (full) ordering w.r.t. the
>solution described by Prateek and Peter. Also, it will "trade" two lwsync
>for two sync (powerpc), one dmb.ld for one dmb (arm64).
>
>What are the reasons you would prefer this?

It was mainly to maintain consistency about dealing with sem->count, but sure
I won't argue with the above.

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-07 14:30 Prateek Sood
2017-09-19 14:05 ` Andrea Parri
2017-09-20 14:52 ` Davidlohr Bueso
2017-09-20 21:17   ` Andrea Parri
2017-09-27 21:20     ` Davidlohr Bueso [this message]
2017-09-26 18:37 ` Prateek Sood
2017-09-29  9:30 ` [tip:locking/urgent] locking/rwsem-xadd: Fix " tip-bot for Prateek Sood
  -- strict thread matches above, loose matches on Subject: below --
2017-08-23 11:28 [PATCH] rwsem: fix " Prateek Sood
2017-08-24 11:29 ` Peter Zijlstra
2017-08-24 12:33   ` Peter Zijlstra
2017-08-24 12:52     ` Peter Zijlstra
2017-09-07 14:08       ` Prateek Sood
2017-07-26 20:17 Prateek Sood
2017-07-27 15:48 ` Waiman Long
2017-07-27 16:59   ` Peter Zijlstra
2017-08-10  8:32   ` Andrea Parri
2017-08-10 10:41     ` Peter Zijlstra
2017-08-10 10:44 ` Peter Zijlstra

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