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Wed, 05 Feb 2025 10:45:25 -0800 (PST) Message-ID: <35d4b9be-3d08-4eaa-8750-7b34ec6e6064@kernel.dk> Date: Wed, 5 Feb 2025 11:45:24 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 05/12] io_uring: Use helper function hrtimer_update_function() To: Nam Cao , Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , linux-kernel@vger.kernel.org References: <9b33f490fb1d207d3918ef5e116dc3412ae35c1e.1738746927.git.namcao@linutronix.de> Content-Language: en-US From: Jens Axboe In-Reply-To: <9b33f490fb1d207d3918ef5e116dc3412ae35c1e.1738746927.git.namcao@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/5/25 3:55 AM, Nam Cao wrote: > The field 'function' of struct hrtimer should not be changed directly, as > the write is lockless and a concurrent timer expiry might end up using the > wrong function pointer. > > Switch to use hrtimer_update_function() which also performs runtime checks > that it is safe to modify the callback. > > Signed-off-by: Nam Cao > Cc: Jens Axboe > --- > io_uring/io_uring.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c > index ceacf6230e34..936f8b4106cf 100644 > --- a/io_uring/io_uring.c > +++ b/io_uring/io_uring.c > @@ -2421,7 +2421,7 @@ static enum hrtimer_restart io_cqring_min_timer_wakeup(struct hrtimer *timer) > goto out_wake; > } > > - iowq->t.function = io_cqring_timer_wakeup; > + hrtimer_update_function(&iowq->t, io_cqring_timer_wakeup); > hrtimer_set_expires(timer, iowq->timeout); > return HRTIMER_RESTART; > out_wake: The timer is known expired here, it's inside the callback. Is this really necessary or useful? -- Jens Axboe