Messages in this thread | | | Date | Mon, 17 Mar 2014 10:40:20 -0400 | From | Tejun Heo <> | Subject | Re: [PATCH] backing_dev: Fix hung task on sync |
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Hello,
On Sun, Mar 16, 2014 at 12:13:55PM -0700, dbasehore . wrote: > There's already behavior that is somewhat like that with the current > implementation. If there's an item on a workqueue, it could run at any > time. From the perspective of the driver/etc. that is using the > workqueue, there should be no difference between work being on the > workqueue and the kernel triggering a schedule right after the work is > removed from the workqueue, but before the work function has done > anything.
It is different. mod_delayed_work() *guarantees* that the target work item will become pending for execution at least after the specified time has passed. What you're suggesting removes any semantically consistent meaning of the API.
> So to reiterate, calling mod_delayed_work on something that is already > in the workqueue has two behaviors. One, the work is dispatched before > mod_delayed_work can remove it from the workqueue. Two, > mod_delayed_work removes it from the workqueue and sets the timer (or > not in the case of 0). The behavior of the proposed change should be > no different than the first behavior.
No, mod_delayed_work() does *one* thing - the work item is queued for the specified delay no matter the current state of the work item. It is *guaranteed* that the work item will go pending after the specified time. That is the sole meaning of the API.
> This should not introduce new behavior from the perspective of the > code using delayed_work. It is true that there is a larger window of > time between when you call mod_delayed_work and when an already queued > work item will run, but I don't believe that matters.
You're completely misunderstanding the API. Plesae re-read it and understand what it does first.
Thanks.
-- tejun
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