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From: Peter Zijlstra <peterz@infradead.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: io-uring@vger.kernel.org, stable@vger.kernel.org,
	Josef <josef.grieb@gmail.com>, Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 2/2] io_uring: use TWA_SIGNAL for task_work if the task isn't running
Date: Mon, 10 Aug 2020 22:32:40 +0200	[thread overview]
Message-ID: <20200810203240.GE3982@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <faf2c2ae-834e-8fa2-12f3-ae07f8a68e14@kernel.dk>

On Mon, Aug 10, 2020 at 02:25:48PM -0600, Jens Axboe wrote:
> On 8/10/20 2:13 PM, Jens Axboe wrote:
> >> Would it be clearer to write it like so perhaps?
> >>
> >> 	/*
> >> 	 * Optimization; when the task is RUNNING we can do with a
> >> 	 * cheaper TWA_RESUME notification because,... <reason goes
> >> 	 * here>. Otherwise do the more expensive, but always correct
> >> 	 * TWA_SIGNAL.
> >> 	 */
> >> 	if (READ_ONCE(tsk->state) == TASK_RUNNING) {
> >> 		__task_work_notify(tsk, TWA_RESUME);
> >> 		if (READ_ONCE(tsk->state) == TASK_RUNNING)
> >> 			return;
> >> 	}
> >> 	__task_work_notify(tsk, TWA_SIGNAL);
> >> 	wake_up_process(tsk);
> > 
> > Yeah that is easier to read, wasn't a huge fan of the loop since it's
> > only a single retry kind of condition. I'll adopt this suggestion,
> > thanks!
> 
> Re-write it a bit on top of that, just turning it into two separate
> READ_ONCE, and added appropriate comments. For the SQPOLL case, the
> wake_up_process() is enough, so we can clean up that if/else.
> 
> https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-5.9&id=49bc5c16483945982cf81b0109d7da7cd9ee55ed

OK, that works for me, thanks!

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

  reply	other threads:[~2020-08-10 20:32 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-08 18:34 [PATCHSET 0/2] io_uring: use TWA_SIGNAL more carefully Jens Axboe
2020-08-08 18:34 ` [PATCH 1/2] kernel: split task_work_add() into two separate helpers Jens Axboe
2020-08-10 11:37   ` peterz
2020-08-10 15:01     ` Jens Axboe
2020-08-10 15:28       ` peterz
2020-08-10 17:51       ` Jens Axboe
2020-08-10 19:53         ` Peter Zijlstra
2020-08-08 18:34 ` [PATCH 2/2] io_uring: use TWA_SIGNAL for task_work if the task isn't running Jens Axboe
2020-08-10 11:42   ` peterz
2020-08-10 15:02     ` Jens Axboe
2020-08-10 19:21       ` Jens Axboe
2020-08-10 20:12         ` Peter Zijlstra
2020-08-10 20:13           ` Jens Axboe
2020-08-10 20:25             ` Jens Axboe
2020-08-10 20:32               ` Peter Zijlstra [this message]
2020-08-10 20:35                 ` Jens Axboe
2020-08-10 20:35               ` Jann Horn
2020-08-10 21:06                 ` Jens Axboe
2020-08-10 21:10                   ` Peter Zijlstra
2020-08-10 21:12                     ` Jens Axboe
2020-08-10 21:26                       ` Jann Horn
2020-08-10 21:28                         ` Jens Axboe
2020-08-10 22:01                           ` Jens Axboe
2020-08-10 22:41                             ` Jann Horn
2020-08-11  1:25                               ` Jens Axboe
2020-08-11  6:45                               ` Oleg Nesterov
2020-08-11  6:56                                 ` Peter Zijlstra
2020-08-11  7:14                                   ` Oleg Nesterov
2020-08-11  7:26                                     ` Oleg Nesterov
2020-08-11  7:49                                       ` Peter Zijlstra
2020-08-11  7:45                                     ` Peter Zijlstra
2020-08-11  8:10                                       ` Oleg Nesterov
2020-08-11 13:06                                         ` Jens Axboe
2020-08-11 14:05                                           ` Oleg Nesterov
2020-08-11 14:12                                             ` Jens Axboe
2020-08-10 21:27                       ` Jens Axboe
2020-08-10 20:16           ` Jens Axboe
2020-08-13 16:25   ` Sasha Levin
2020-08-19 23:57   ` Sasha Levin
2020-08-19 23:59     ` Jens Axboe
2020-08-20  0:02       ` Jens Axboe

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