On Sun, Dec 10, 2006 at 09:26:16AM +0100, Ingo Molnar wrote:
> something like the pseudocode further below - when applied to a data
> structure it has semantics and scalability close to that of
> preempt_disable(), but it is still preemptible and the lock is specific.
Ingo,
The psuedo-code you have provided can still fail to avoid
the deadlock reported by Bjorn Helgaas earlier in this thread:
http://lkml.org/lkml/2006/12/6/352
Thread1->flush_workqueue->mutex_lock(cpu4's hotplug_lock)
Thread2(keventd)->run_workqueue->som_work_fn-> ..
flush_workqueue->mutex_lock(cpu4's hotplug_lock)
Both deadlock with each other.
All this mess could easily be avoided if we implement a reference-count
based cpu_hotplug_lock(), as suggested by Arjan and Linus before and
implemented by Gautham here:
http://lkml.org/lkml/2006/10/26/65
--
Regards,
vatsa
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