Messages in this thread | | | Date | Wed, 9 Sep 2009 15:46:38 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/1] sched: fix cpu_down deadlock |
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On 09/09, Jiri Slaby wrote: > > On 09/09/2009 01:53 PM, Peter Zijlstra wrote: > > On Wed, 2009-09-09 at 13:41 +0200, Jiri Slaby wrote: > >> Jiri Slaby wrote: > >>> Thanks, in the end I found it manually. Goddammit! It's an -mm thing: > >>> cpu_hotplug-dont-affect-current-tasks-affinity.patch > > > > Is there a git tree with -mm in some place? I can't seem to find that > > patch in my inbox. > > > > All I can find is some comments from Oleg that the patch looks funny. > > Yes, here: > git://git.zen-sources.org/zen/mmotm.git > > Actually I found Oleg came up with better solution to add > move_task_off_dead_cpu to take_cpu_down. > > A discussion regarding this is at: > http://lkml.indiana.edu/hypermail/linux/kernel/0907.3/02278.html > > So what's the status of the patches, please?
This patch depends on another one, please see
"[PATCH] cpusets: rework guarantee_online_cpus() to fix deadlock with cpu_down()" http://marc.info/?t=124910242400002
(as the changelog says, the patch is not complete: we need ->cpumask_lock every time we update cs->allowed, but this should be trivial)
In short: cpuset_lock() is buggy. But more importantly it is afaics unneeded, and imho should die. I seem to answer all Lai's questions, but the patch was ignored by maintainers.
I noticed another race in update_cpumask() which I was going to fix, but since maintainers ignore me I lost the motivtion ;) Besides, currently I dont have the time anyway.
So I think the original patch which creates the kthread is the best option.
Oleg.
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