Re: [Experimental CPU Hotplug PATCH] - Move migrate_all_tasks to CPU_DEAD handling

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

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