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SubjectRe: [PATCH] workqueue: Document exceptions to work item non-reentrancy guarantee
On Mon, Feb 17, 2014 at 09:29:34PM -0500, Peter Hurley wrote:
> >It never would have occurred to me that you could safely change the
> >function for a work item that is already scheduled or running.
> >Especially given that PREPARE_WORK() is just a simple assignment (i.e.
> >no serialisation).
>
> process_one_work() has an established order that safely allows for
> resetting the work function and scheduling the work, and further
> guaranteeing that the new work function will run.
>
> Further, existing memory barriers ensure that
> 1. The new work function is visible on all cpus before testing if
> the work is already pending.
> 2. The new work function is stored as the worker's current function
> before the work is marked as not pending.
>
> If this wasn't possible, then single-threaded workqueues could
> not be used for multiple functions without flushing work.
>
> I wonder if the floppy driver is broken too.

Ugh... I'd just rather remove PREPARE_WORK altogether. It's a pretty
dumb thing to do anyway. I'll look into it.

Thanks.

--
tejun


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