Messages in this thread | | | Date | Mon, 26 Jan 2009 23:31:45 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 2/3] work_on_cpu: Use our own workqueue. |
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On 01/26, Andrew Morton wrote: > > On Mon, 26 Jan 2009 23:05:37 +0100 > Ingo Molnar <mingo@elte.hu> wrote: > > > > > * Andrew Morton <akpm@linux-foundation.org> wrote: > > > > > Well it turns out that I was having a less-than-usually-senile moment: > > > > > > : implement flush_work() > > > > > Why isn't that working in this case?? > > > > how would that work in this case? We defer processing into the workqueue > > exactly because we want its per-CPU properties. > > It detaches the work item, moves it to head-of-queue, reinserts it then > waits on it. I think.
No, no helper works this way.
The reinsert doesn't make sense for cancel_work.
As for flush_work(), I think it is possible to do, but can't help to avoid the deadlocks. Because we still have to wait for ->current_work.
> This might have a race+hole. If a currently-running "unrelated" > work item tries to take the lock which the flush_work() caller is holding > then there's no way in which keventd will come back to execute > the work item which we just put on the head of queue.
Yes.
> > We want work_on_cpu() to > > be done in the workqueue context on the CPUs that were specified, not in > > the local CPU context. > > flush_work() is supposed to work in the way which you describe.
Yes,
> But Oleg's "we may be running on a different CPU" comment has me all > confused.
I meant, that
> the caller of flush_work() can detach the work item > and run it directly.
this is not possible in work_on_cpu() case, we can't run it directly, we want it to run on the target CPU.
Oleg.
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