Re: [PATCH] fix-flush_workqueue-vs-cpu_dead-race-update

[Srivatsa Vaddagiri <vatsa@in.ibm.com>]

On Sat, Jan 06, 2007 at 07:30:35PM +0300, Oleg Nesterov wrote:
> Stupid me. Thanks.
> 
> I'll try to do something else tomorrow. Do you see a simple soulution?

Sigh ..I dont see a simple solution, unless we have something like
lock_cpu_hotplug() ..

Andrew,
	This workqueue problem has exposed a classic example of how 
tough/miserable it can be to write hotplug safe code w/o something like
lock_cpu_hotplug() ..Are you still inclined towards banning it? :)

FYI, the lock_cpu_hotplug() rewrite proposed by Gautham at
http://lkml.org/lkml/2006/10/26/65 may still need refinement to avoid
all the kind of deadlocks we have unearthed with workqueue example. I
can review that design with Gautham if there is some interest to
revive lock_cpu_hotplug() ..

> The current usage of workqueue_mutex (I mean stable kernel) is broken
> and deadlockable. We really need to change it.

Yep ..

-- 
Regards,
vatsa
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