Messages in this thread | | | Date | Wed, 21 Feb 2007 20:07:51 +0530 | From | Gautham R Shenoy <> | Subject | Re: [RFC PATCH(Experimental) 2/4] Revert changes to workqueue.c |
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On Wed, Feb 21, 2007 at 05:30:10PM +0300, Oleg Nesterov wrote: > On 02/21, Srivatsa Vaddagiri wrote: > > > > On Tue, Feb 20, 2007 at 11:09:36PM +0300, Oleg Nesterov wrote: > > > > Which caller are you referring to here? Maybe we can decide on the > > > > option after we see the users of flush_workqueue() in DOWN_PREPARE. > > > > > > mm/slab.c:cpuup_callback() > > > > The cancel_rearming_delayed_work, if used as it is in cpuup_callback, > > will require that we send DOWN_PREPARE before freeze_processes(). > > > > But ..I am wondering if we can avoid doing cancel_rearming_delayed_work > > (and thus flush_workqueue) in CPU_DOWN_PREPARE of slab.c. Basically, > > > > mm/slab.c: > > > > CPU_DOWN_PREPARE: /* All processes frozen now */ > > cancel_delayed_work(&per_cpu(reap_work, cpu).timer); > > del_work(&per_cpu(reap_work, cpu).work); > > break; > > > > > > At the point of CPU_DOWN_PREPARE, keventd should be frozen and hence > > del_work() is a matter of just deleting the work from cwq->worklist. > > Agreed. Note that we don't need the new "del_work". It is always safe to > use cancel_work_sync() if we know that the workqueue is frozen, it won't > block. We can also do > > if (!cancel_delayed_work()) > cancel_work_sync(); > > but it is ok to do cancel_work_sync() unconditionally.
True. But this might be a one off solution for slab. However, if someone in the future might require to do a flush_workqueue from CPU_DOWN_PREPARE context, we would need to find a new workaround.
So, I'll try running CPU_DOWN_PREPARE and CPU_UP_PREPARE from a non frozen context to check if there are any potential problems. Hopfully there shouldn't be (m)any! > > Oleg. > thanks and regards gautham.
-- Gautham R Shenoy Linux Technology Center IBM India. "Freedom comes with a price tag of responsibility, which is still a bargain, because Freedom is priceless!" - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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