Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <3e2ba7d7-0431-7558-2ece-89ce266f7792@kernel.dk>
Date:   Wed, 12 Jul 2023 09:02:52 -0600
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:102.0) Gecko/20100101
 Thunderbird/102.12.0
Subject: Re: [PATCH 2/7] futex: factor out the futex wake handling
Content-Language: en-US
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     io-uring@vger.kernel.org, linux-kernel@vger.kernel.org,
        tglx@linutronix.de, mingo@redhat.com
References: <20230712004705.316157-1-axboe@kernel.dk>
 <20230712004705.316157-3-axboe@kernel.dk>
 <20230712085803.GD3100107@hirez.programming.kicks-ass.net>
From:   Jens Axboe <axboe@kernel.dk>
In-Reply-To: <20230712085803.GD3100107@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 7/12/23 2:58?AM, Peter Zijlstra wrote:
> On Tue, Jul 11, 2023 at 06:47:00PM -0600, Jens Axboe wrote:
>> In preparation for having another waker that isn't futex_wake_mark(),
>> add a wake handler in futex_q. No extra data is associated with the
>> handler outside of struct futex_q itself. futex_wake_mark() is defined as
>> the standard wakeup helper, now set through futex_q_init like other
>> defaults.
> 
> Urgh... so if I understand things right, you're going to replace this
> with a custom wake function that does *NOT* put the task on the wake_q.
> 
> The wake_q will thus be empty and the task does not get woken up. I'm
> presuming someone gets a notification instead somewhere somehow.

Right. The custom wake function is responsible for waking the task, if
that is what needs to happen. On the io_uring side, the callback would
queue work for the original task to post a completion event, which would
then also wake it up obviously.

> I might've been nice to mention some of this somewhere ...

I'll expand the commit message a bit, it is a bit light.

-- 
Jens Axboe