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Date:   Fri, 19 Jul 2019 10:49:56 +0200
From:   Andrea Parri <andrea.parri@amarulasolutions.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Will Deacon <will@kernel.org>, linux-kernel@vger.kernel.org,
        Jan Stancek <jstancek@redhat.com>,
        Waiman Long <longman@redhat.com>, dbueso@suse.de,
        mingo@redhat.com, jade.alglave@arm.com, paulmck@linux.vnet.ibm.com
Subject: Re: [PATCH 1/4] locking/rwsem: Add missing ACQUIRE to read_slowpath
 exit when queue is empty
Message-ID: <20190719084956.GA6750@andrea>
References: <20190718134954.496297975@infradead.org>
 <20190718135205.916241783@infradead.org>
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> @@ -1032,6 +1032,8 @@ rwsem_down_read_slowpath(struct rw_semap
>  		 */
>  		if (adjustment && !(atomic_long_read(&sem->count) &
>  		     (RWSEM_WRITER_MASK | RWSEM_FLAG_HANDOFF))) {
> +			/* Provide lock ACQUIRE */
> +			smp_acquire__after_ctrl_dep();

Does this also make the lock RCtso?  Or maybe RCtso was already
guaranteed (and I'm failing to see why)?

Thanks,
  Andrea