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 12:32:13 +0100 [thread overview]
Message-ID: <20161205113212.GA31288@redhat.com> (raw)
In-Reply-To: <20161205112636.GA30280@redhat.com>
On 12/05, Oleg Nesterov wrote:
>
> Yes, but on a second thought task_rcu_dereference() won't really help,
I forgot to explain why, see below.
> #define xxx_wait_event(xxx, event) {
> // comment to explain why
> WARN_ON(current->exit_state);
Otherwise this process/thread can be already (auto)reaped and wakeup
can't rely on rcu.
And task_rcu_dereference() can't help because it can return NULL in
this case.
Oleg.
next prev parent reply other threads:[~2016-12-05 11:43 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 [this message]
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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