From: Amir Goldstein <amir73il@gmail.com>
To: Waiman Long <longman@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
"Theodore Y. Ts'o" <tytso@mit.edu>,
Oleg Nesterov <oleg@redhat.com>, Jan Kara <jack@suse.cz>
Subject: Re: [RFC PATCH v2 1/2] locking/rwsem: Add a new RWSEM_WRITER_OWNED_NOSPIN flag
Date: Tue, 15 May 2018 09:59:14 +0300 [thread overview]
Message-ID: <CAOQ4uxgMHKeVNS7Mg2nG=Zt_sGGOr1d20gA-s7Q8hhe-zA+kLw@mail.gmail.com> (raw)
In-Reply-To: <1526326267-22501-2-git-send-email-longman@redhat.com>
On Mon, May 14, 2018 at 10:31 PM, Waiman Long <longman@redhat.com> wrote:
> There are use cases where a rwsem can be acquired by one task, but
> released by another task. In thess cases, it may not be appropriate
> for the lock waiters to spin on the task that acquires the lock.
> One example will be the filesystem freeze/thaw code.
>
> To handle such use cases, a new RWSEM_WRITER_OWNED_NOSPIN
> flag can now be set in the owner field of the rwsem by the new
> rwsem_set_writer_owned_nospin() function to indicate that the rwsem is
> writer owned, but optimistic spinning on the rwsem should be disabled.
>
> Later on, the new rwsem_set_writer_owned() function can be called to
> set the new owner, if it is known. This function should not be called
> without a prior rwsem_set_writer_owned_nospin() call.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
Makes sense to me. one nit.
>
> +static inline void __rwsem_set_writer_owned(struct rw_semaphore *sem,
> + struct task_struct *task)
rwsem_set_owner() doesn't pass in task argument and IMO
__rwsem_set_writer_owned() shouldn't either.
Thanks,
Amir.
next prev parent reply other threads:[~2018-05-15 6:59 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-14 19:31 [RFC PATCH v2 0/2] locking/rwsem: Fix DEBUG_RWSEM warning from thaw_sup Waiman Long
2018-05-14 19:31 ` [RFC PATCH v2 1/2] locking/rwsem: Add a new RWSEM_WRITER_OWNED_NOSPIN flag Waiman Long
2018-05-15 6:59 ` Amir Goldstein [this message]
2018-05-15 8:25 ` Peter Zijlstra
2018-05-14 19:31 ` [RFC PATCH v2 2/2] locking/percpu-rwsem: Mark rwsem as non-spinnable in percpu_rwsem_release() Waiman Long
2018-05-15 5:42 ` Amir Goldstein
2018-05-15 7:04 ` Amir Goldstein
2018-05-15 13:45 ` Waiman Long
2018-05-15 8:35 ` Peter Zijlstra
2018-05-15 9:00 ` Jan Kara
2018-05-15 11:33 ` Oleg Nesterov
2018-05-15 8:51 ` Peter Zijlstra
2018-05-15 11:06 ` Oleg Nesterov
2018-05-15 11:51 ` Peter Zijlstra
2018-05-15 12:45 ` Oleg Nesterov
2018-05-15 12:58 ` Peter Zijlstra
2018-05-15 13:57 ` Waiman Long
2018-05-15 14:00 ` Matthew Wilcox
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