linux-kernel - Re: [RFC PATCH 5/8] vhost: Add callback that stops new work and waits on running ones

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Date:   Thu, 18 May 2023 17:09:11 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Mike Christie <michael.christie@...cle.com>
Cc:     oleg@...hat.com, linux@...mhuis.info, nicolas.dichtel@...nd.com,
        axboe@...nel.dk, ebiederm@...ssion.com,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, mst@...hat.com,
        sgarzare@...hat.com, jasowang@...hat.com, stefanha@...hat.com
Subject: Re: [RFC PATCH 5/8] vhost: Add callback that stops new work and
 waits on running ones

On Thu, May 18, 2023 at 10:03:32AM -0500, Mike Christie wrote:
> On 5/18/23 9:18 AM, Christian Brauner wrote:
> >> @@ -352,12 +353,13 @@ static int vhost_worker(void *data)
> >>  		if (!node) {
> >>  			schedule();
> >>  			/*
> >> -			 * When we get a SIGKILL our release function will
> >> -			 * be called. That will stop new IOs from being queued
> >> -			 * and check for outstanding cmd responses. It will then
> >> -			 * call vhost_task_stop to exit us.
> >> +			 * When we get a SIGKILL we kick off a work to
> >> +			 * run the driver's helper to stop new work and
> >> +			 * handle completions. When they are done they will
> >> +			 * call vhost_task_stop to tell us to exit.
> >>  			 */
> >> -			vhost_task_get_signal();
> >> +			if (vhost_task_get_signal())
> >> +				schedule_work(&dev->destroy_worker);
> >>  		}
> > 
> > I'm pretty sure you still need to actually call exit here. Basically
> > mirror what's done in io_worker_exit() minus the io specific bits.
> 
> We do call do_exit(). Once destory_worker has flushed the device and
> all outstanding IO has completed it call vhost_task_stop(). vhost_worker()
> above then breaks out of the loop and returns and vhost_task_fn() does
> do_exit().

Ah, that callchain wasn't obvious. Thanks.