linux-kernel - Re: [PATCH 2/3] slow-work: add support for cancellation of slow work

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Message-ID: <20090827091409.GF12579@kernel.dk>
Date:	Thu, 27 Aug 2009 11:14:10 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org
Cc:	tj@...nel.org, alan@...rguk.ukuu.org.uk, jeff@...zik.org,
	dhowells@...hat.com
Subject: Re: [PATCH 2/3] slow-work: add support for cancellation of slow
	work

On Thu, Aug 27 2009, Jens Axboe wrote:
> @@ -194,12 +194,21 @@ static bool slow_work_execute(void)
>  	if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags))
>  		BUG();
>  
> -	work->ops->execute(work);
> +	/*
> +	 * Don't execute if the work was cancelled after being added
> +	 */
> +	if (!test_bit(SLOW_WORK_CANCEL, &work->flags))
> +		work->ops->execute(work);
>  
>  	if (very_slow)
>  		atomic_dec(&vslow_work_executing_count);
>  	clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags);
>  
> +	/*
> +	 * Wake anyone waiting for this work to be done
> +	 */
> +	wake_up_bit(&work->flags, SLOW_WORK_EXECUTING);
> +
>  	/* if someone tried to enqueue the item whilst we were executing it,
>  	 * then it'll be left unenqueued to avoid multiple threads trying to
>  	 * execute it simultaneously

> +void cancel_slow_work(struct slow_work *work)
> +{
> +	set_bit(SLOW_WORK_CANCEL, &work->flags);
> +	wait_on_bit(&work->flags, SLOW_WORK_EXECUTING, slow_work_wait,
> +				TASK_UNINTERRUPTIBLE);
> +	clear_bit(SLOW_WORK_CANCEL, &work->flags);
> +}
> +EXPORT_SYMBOL(cancel_slow_work);

We want to use SLOW_WORK_PENDING for this logic, not SLOW_WORK_EXECUTING.
I'll update it.

-- 
Jens Axboe

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