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[109.80.100.86]) by smtp.gmail.com with ESMTPSA id n17sm3750263wrw.77.2019.05.09.23.29.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 09 May 2019 23:29:05 -0700 (PDT) Date: Fri, 10 May 2019 08:27:27 +0200 From: Andrea Parri To: Ming Lei Cc: linux-kernel@vger.kernel.org, Jens Axboe , Omar Sandoval , linux-block@vger.kernel.org Subject: Re: [PATCH 3/5] sbitmap: fix improper use of smp_mb__before_atomic() Message-ID: <20190510062727.GA4607@andrea> References: <1556568902-12464-1-git-send-email-andrea.parri@amarulasolutions.com> <1556568902-12464-4-git-send-email-andrea.parri@amarulasolutions.com> <20190510034101.GC27944@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190510034101.GC27944@ming.t460p> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ming, On Fri, May 10, 2019 at 11:41:02AM +0800, Ming Lei wrote: > On Mon, Apr 29, 2019 at 10:14:59PM +0200, Andrea Parri wrote: > > This barrier only applies to the read-modify-write operations; in > > particular, it does not apply to the atomic_set() primitive. > > > > Replace the barrier with an smp_mb(). > > > > Fixes: 6c0ca7ae292ad ("sbitmap: fix wakeup hang after sbq resize") > > Cc: stable@vger.kernel.org > > Reported-by: "Paul E. McKenney" > > Reported-by: Peter Zijlstra > > Signed-off-by: Andrea Parri > > Cc: Jens Axboe > > Cc: Omar Sandoval > > Cc: linux-block@vger.kernel.org > > --- > > lib/sbitmap.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/lib/sbitmap.c b/lib/sbitmap.c > > index 155fe38756ecf..4a7fc4915dfc6 100644 > > --- a/lib/sbitmap.c > > +++ b/lib/sbitmap.c > > @@ -435,7 +435,7 @@ static void sbitmap_queue_update_wake_batch(struct sbitmap_queue *sbq, > > * to ensure that the batch size is updated before the wait > > * counts. > > */ > > - smp_mb__before_atomic(); > > + smp_mb(); > > for (i = 0; i < SBQ_WAIT_QUEUES; i++) > > atomic_set(&sbq->ws[i].wait_cnt, 1); > > } > > -- > > 2.7.4 > > > > sbitmap_queue_update_wake_batch() won't be called in fast path, and > the fix is correct too, so: > > Reviewed-by: Ming Lei Thank you for the review(s), Andrea > thanks, > Ming