Messages in this thread | | | Date | Tue, 9 Jan 2007 18:07:55 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH] flush_cpu_workqueue: don't flush an empty ->worklist |
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On 01/08, Andrew Morton wrote: > > That's not correct. freeze_processes() will freeze *all* processes. All > of them are forced to enter refrigerator(). With the mysterious exception > of some I/O-related kernel threads, which might need some thought.
Yes, and we can remove a dead CPU safely, this part is ok.
> > and > > http://marc.theaimsgroup.com/?l=linux-kernel&m=116817460726058. > > Am not sure how that's related.
but at some point we should thaw processes, including cwq->thread which should die. So we are doing things like take_over_work() and this is the source of races, because the dead CPU is not on cpu_online_map.
flush_workqueue() doesn't use any locks now. If we use freezer to implement cpu-hotplug nothing will change, we still have races.
It looks so obvious to me, so I'm starting to suspect I missed something very simple :(
Oleg.
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