From: Oleg Nesterov <oleg@redhat.com>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: mingo@kernel.org, peterz@infradead.org, john.stultz@linaro.org,
dimitrysh@google.com, linux-kernel@vger.kernel.org,
Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH 2/3] locking/percpu-rwsem: Replace bulky wait-queues with swait
Date: Mon, 21 Nov 2016 13:55:35 +0100 [thread overview]
Message-ID: <20161121125535.GB1459@redhat.com> (raw)
In-Reply-To: <1479495277-9075-3-git-send-email-dave@stgolabs.net>
On 11/18, Davidlohr Bueso wrote:
>
> @@ -12,7 +12,7 @@ struct percpu_rw_semaphore {
> struct rcu_sync rss;
> unsigned int __percpu *read_count;
> struct rw_semaphore rw_sem;
> - wait_queue_head_t writer;
> + struct swait_queue_head writer;
I won't argue, but even swait_queue_head is overkill in this case.
We can just add "struct task_struct *writer" into percpu_rw_semaphore,
__percpu_up_read:
rcu_read_lock();
writer = task_rcu_dereference(&sem->writer);
if (writer)
wake_up_process(writer);
rcu_read_unlock();
percpu_down_write() can set sem->writer == current and do the simple
while-not-condition-schedule() loop.
But this probably needs a couple of new helpers, and probably they
can have more users.
Oleg.
next prev parent reply other threads:[~2016-11-21 12:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-18 18:54 [PATCH -tip 0/3] locking/percpu-rwsem: writer-side optimizations Davidlohr Bueso
2016-11-18 18:54 ` [PATCH 1/3] locking/percpu-rwsem: Move text file into Documentation/locking/ Davidlohr Bueso
2016-11-18 18:54 ` [PATCH 2/3] locking/percpu-rwsem: Replace bulky wait-queues with swait Davidlohr Bueso
2016-11-21 12:55 ` Oleg Nesterov [this message]
2016-11-21 17:26 ` Davidlohr Bueso
2016-12-03 2:18 ` [PATCH v2 2/3] locking/percpu-rwsem: Rework writer block/wake to not use wait-queues Davidlohr Bueso
2016-12-05 8:36 ` Peter Zijlstra
2016-12-05 11:26 ` Oleg Nesterov
2016-12-05 11:32 ` Oleg Nesterov
2016-12-05 17:37 ` Davidlohr Bueso
2016-12-05 17:19 ` Oleg Nesterov
2016-12-05 17:13 ` Oleg Nesterov
2016-11-18 18:54 ` [PATCH 3/3] locking/percpu-rwsem: Avoid unnecessary writer wakeups Davidlohr Bueso
2016-11-21 12:23 ` Oleg Nesterov
2016-11-21 12:29 ` Peter Zijlstra
2016-11-21 12:47 ` Oleg Nesterov
2016-11-21 15:07 ` Oleg Nesterov
2016-11-22 3:59 ` Davidlohr Bueso
2016-11-23 14:43 ` Oleg Nesterov
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