From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
mingo@kernel.org, john.stultz@linaro.org, dimitrysh@google.com,
linux-kernel@vger.kernel.org, Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH v2 2/3] locking/percpu-rwsem: Rework writer block/wake to not use wait-queues
Date: Mon, 5 Dec 2016 18:19:17 +0100 [thread overview]
Message-ID: <20161205171916.GC13035@redhat.com> (raw)
In-Reply-To: <20161205083605.GQ3092@twins.programming.kicks-ass.net>
On 12/05, Peter Zijlstra wrote:
>
> > + for (;;) {
> > + set_current_state(TASK_UNINTERRUPTIBLE);
> > +
> > + if (readers_active_check(sem))
> > + break;
> > +
> > + schedule();
> > + }
> > +
> > + rcu_assign_pointer(sem->writer, NULL);
>
> And this one does not, and the value being NULL this actually reverts to
> WRITE_ONCE().
Do we really care? We do not even need WRITE_ONCE() afaics, this is like
__set_current_state(TASK_RUNNING) after the main loop. We can't avoid the
spurious wakeups anyway after return from percpu_down_write().
Oleg.
next prev parent reply other threads:[~2016-12-05 17:19 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
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 [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161205171916.GC13035@redhat.com \
--to=oleg@redhat.com \
--cc=dave@stgolabs.net \
--cc=dbueso@suse.de \
--cc=dimitrysh@google.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.