Messages in this thread | | | Subject | Re: [PATCH 1/3] stop_machine: kill __stop_machine() | From | Suresh Siddha <> | Date | Thu, 16 Jun 2011 11:44:31 -0700 |
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On Thu, 2011-06-16 at 11:36 -0700, Peter Zijlstra wrote: > On Thu, 2011-06-16 at 20:28 +0200, Tejun Heo wrote: > > Peter, I don't think it's that simple. get_online_cpus() itself can't > > create circular dependency by itself. It allows recursing. The chain > > involves cpu_hotplug_begin() which returns with hotplug mutex held. > > > Right, its like: > > mutex_lock(&a); > get_online_cpus(); > > vs > > cpu_hotplug_begin() > mutex_lock(&a); > > > that will really deadlock
Its actually like:
get_online_cpus(); mutex_lock(&a); get_online_cpus(); <--- recursive get_online_cpus()
vs
cpu_hotplug_begin() mutex_lock(&a);
So it can't cause deadlock in practice.
thanks, suresh
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