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 10:03:32 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     Christian Brauner <brauner@...nel.org>
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 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().