On Tue, May 08, 2007 at 04:02:21PM +0400, Oleg Nesterov wrote: > On 05/08, Jarek Poplawski wrote: > > > > On Mon, May 07, 2007 at 02:34:20PM +0400, Oleg Nesterov wrote: > > > On 05/07, Jarek Poplawski wrote: ... > I am strongly against adding many different variants of cancel_xxx(). > With this patch the API is simple > > - cancel_delayed_work() stops the timer > > - cancel_rearming_delayed_work() stops the timer and work, > doesn't need cancel_work_sync/flush_workqueue
But most often there is a simple rearming (but not neccessarily always) work for which the first is not enough and the second an overkill (especially with system/workqueues loaded). > When work->func() re-arms itself, both queue_work() and queue_delayed_work() > may change CPU if CPU_DOWN_xxx happens. Note that this is possible > even if we use freezer for cpu-hotplug, because the timer migrates to > another CPU anyway. Thanks for explanation - I try to think about this. > > I'm not sure what exactly place > > did you mean - if spinlocking in wait_on_work - maybe it's > > a sign this place isn't optimal too: it seems to me, this all > > inserting/waiting for completion could be done under existing > > locks e.g. in run_workqueue (maybe with some flag?). > > Sorry, can't understand this. Inserting uses existing lock, namely > cwq->lock. I meant held locks - maybe e.g. after seeing some flag set (or some other global/per_cpu/atomic/whatever variable) in a processed work insert_wq_barrier could be done in already locked place. Or maybe the whole idea of these completions should be rethinked, for something lighter (i.e. lockless)? > > Just in case, I think wait_on_cpu_work() can check ->current_work without > cwq->lock, but I am not sure yet. We can remove unneeded "new |= " from > set_wq_data(), we can do a couple of other optimizations. However, there > are already _a lot_ of workqueue changes in -mm tree. We can do this later. > Right now my only concern is correctness. I agree 100% - it's -mm, the old way is working, so why hurry? Jarek P. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
