Messages in this thread | | | Date | Sun, 7 Jan 2007 20:18:26 +0300 | From | Oleg Nesterov <> | Subject | Re: [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update |
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On 01/07, Srivatsa Vaddagiri wrote: > > On Sun, Jan 07, 2007 at 05:22:46PM +0300, Oleg Nesterov wrote: > > On 01/07, Oleg Nesterov wrote: > > > > > > Thoughts? > > > > How about: > > > > CPU_DEAD does nothing. After __cpu_disable() cwq->thread runs on > > all CPUs and becomes idle when it flushes cwq->worklist: nobody > ^^^ > > all except dead cpus that is.
yes, of course.
> > > will add work_struct on that list. > > If CPU_DEAD does nothing, then the dead cpu's workqueue list may be > non-empty. How will it be flushed, given that no thread can run on the > dead cpu?
But cwq->thread is not bound to the dead CPU at this point, it was aleady migrated (like all other threads which had that CPU in ->cpus_allowed).
> Finally, I am concerned about the (un)friendliness of this programming > model, where programmers are restricted in not having a stable access to > cpu_online_map at all -and- also requiring them to code in non-obvious > terms. Granted that writing hotplug-safe code is non-trivial, but the > absence of "safe access to online_map" will make it more complicated.
I guess you misunderstood me, I meant CPU_DEAD does nothing only in workqueue.c:workqueue_cpu_callback().
Oleg.
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