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SubjectRe: [Experimental CPU Hotplug PATCH] - Move migrate_all_tasks to CPU_DEAD handling
On Wed, Apr 07, 2004 at 01:54:34PM +1000, Rusty Russell wrote:
> No, it really is required.
>
> The stop_machine thread runs on the cpu, then kicks everyone else off,
> then does a complete() (in stop_machine.c:do_stop()). Without this
> check, the complete() drags the sleeping process (which called
> stop_machine) onto the dying CPU.

Precisely. That's why I ended up adding this in cpu_down!!


+ /* Ensure that we are not runnable on dying cpu */
+ old_allowed = current->cpus_allowed;
+ tmp = CPU_MASK_ALL;
+ cpu_clear(cpu, tmp);
+ set_cpus_allowed(current, tmp);
I restore the mask though (under covers of lock_cpu_hotplug) before
returning from cpu_down. Task should never see this violated affinity.

Rusty,
What do you think abt the whole patch? It has withstood
my stress-test harness :-)


--


Thanks and Regards,
Srivatsa Vaddagiri,
Linux Technology Center,
IBM Software Labs,
Bangalore, INDIA - 560017
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