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Message-ID: <20180516121947.GE20670@bombadil.infradead.org>
Date: Wed, 16 May 2018 05:19:47 -0700
From: Matthew Wilcox <willy@...radead.org>
To: Waiman Long <longman@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
Davidlohr Bueso <dave@...olabs.net>,
"Theodore Y. Ts'o" <tytso@....edu>,
Oleg Nesterov <oleg@...hat.com>,
Amir Goldstein <amir73il@...il.com>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH v4 1/2] locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED
flag
On Tue, May 15, 2018 at 05:49:50PM -0400, Waiman Long wrote:
> @@ -357,11 +357,8 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
>
> rcu_read_lock();
> owner = READ_ONCE(sem->owner);
> - if (!rwsem_owner_is_writer(owner)) {
> - /*
> - * Don't spin if the rwsem is readers owned.
> - */
> - ret = !rwsem_owner_is_reader(owner);
> + if (!owner || !is_rwsem_owner_spinnable(owner)) {
> + ret = !owner; /* !owner is spinnable */
> goto done;
> }
This is confusingly written. I think you mean ...
if (!owner)
goto done;
if (!is_rwsem_owner_spinnable(owner)) {
ret = false;
goto done;
}
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