linux-kernel - Re: [ANNOUNCE] v5.14-rc4-rt4

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Message-ID: <f2d0a028-fe85-28ff-9cea-8ab1d26a15d0@kernel.dk>
Date:   Wed, 4 Aug 2021 09:39:30 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Daniel Wagner <wagi@...om.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [ANNOUNCE] v5.14-rc4-rt4

On 8/4/21 9:33 AM, Sebastian Andrzej Siewior wrote:
> On 2021-08-04 08:23:55 [-0600], Jens Axboe wrote:
>> Totally untested, but I think the principle is sound. I'll run it through
>> some testing.
> 
> This is needed:
> 
> diff --git a/fs/io-wq.c b/fs/io-wq.c
> index 1192ee2abd982..77ec6896edaa5 100644
> --- a/fs/io-wq.c
> +++ b/fs/io-wq.c
> @@ -428,9 +428,9 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
>  	}
>  
>  	if (stall_hash != -1U) {
> -		raw_spin_unlock(&wqe->lock);
> +		raw_spin_unlock_irq(&wqe->lock);
>  		io_wait_on_hash(wqe, stall_hash);
> -		raw_spin_lock(&wqe->lock);
> +		raw_spin_lock_irq(&wqe->lock);
>  	}
>  
>  	return NULL;
> 
> 
> otherwise the spinlock_t lock in io_wait_on_hash() is acquired with
> disabled interrupts which is a no-no on -RT.
> With that it all looks good as far as I can tell.
> Thank you.

I'm confused, the waitqueue locks are always IRQ disabling.

-- 
Jens Axboe