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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] task_work: cleanup notification modes
In-Reply-To: <7e32aa44-35ff-3a48-87d0-8e7df586db1d@kernel.dk>
References: <93292d5b-9124-d252-c81f-1f2cfbd60e7b@kernel.dk> <87tuutalre.fsf@nanos.tec.linutronix.de> <aaed79d1-972f-e4bd-f3ac-d589cd729163@kernel.dk> <87zh4lix8l.fsf@nanos.tec.linutronix.de> <2ebe7e45-b4e5-1a6b-d3ee-4a790817a119@kernel.dk> <87wnzpivvx.fsf@nanos.tec.linutronix.de> <7e32aa44-35ff-3a48-87d0-8e7df586db1d@kernel.dk>
Date:   Sat, 17 Oct 2020 17:31:42 +0200
Message-ID: <87tuusj2ch.fsf@nanos.tec.linutronix.de>
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On Fri, Oct 16 2020 at 17:43, Jens Axboe wrote:
> On 10/16/20 5:38 PM, Thomas Gleixner wrote:
> If you know the task isn't exiting, then yeah you can ignore it. But
> seems a bit dicey...

Indeed.

>> fs/io_uring.c-	if (unlikely(ret)) {
>> fs/io_uring.c-		struct task_struct *tsk;
>> fs/io_uring.c-
>> fs/io_uring.c-		init_task_work(&req->task_work, io_req_task_cancel);
>> fs/io_uring.c-		tsk = io_wq_get_task(req->ctx->io_wq);
>> fs/io_uring.c:		task_work_add(tsk, &req->task_work, 0);
>> fs/io_uring.c-		wake_up_process(tsk);
>> 
>> yet more magic wakeup.
>
> It's not magic, but probably needs a comment... If we fail, that task is
> exiting. But we know we have our io-wq threads, so we use that as a
> fallback. Not really expected in the fast path.

I somehow misread it. So ignore me.

Thanks,

        tglx