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SubjectRe: current linux-2.6.git: cpusets completely broken
2008/7/11 Vegard Nossum <vegard.nossum@gmail.com>:
> On Fri, Jul 11, 2008 at 9:36 PM, Paul Menage <menage@google.com> wrote:
>> On Fri, Jul 11, 2008 at 12:07 PM, Vegard Nossum <vegard.nossum@gmail.com> wrote:
>>>
>>> The result of having CPUSETS enabled as above is a 100% reproducible
>>> BUG on the very first cpu hot-unplug:
>>>
>>> ------------[ cut here ]------------
>>> kernel BUG at xxx/linux-2.6/kernel/sched.c:5859!
>>
>> That doesn't quite match up with any BUG in 2.6.26-rc9 - what tree is
>> this last crash based on?
>
> latest mainline. Commit e5a5816f7875207cb0a0a7032e39a4686c5e10a4.
>
> Is this one:
>
> /* called under rq->lock with disabled interrupts */
> static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
> {
> struct rq *rq = cpu_rq(dead_cpu);
>
> /* Must be exiting, otherwise would be on tasklist. */
> BUG_ON(!p->exit_state);
>
>>> Also, this is on the latest linux-2.6.git! Since we're so close to
>>> release, maybe cpusets should simply be marked BROKEN for now? (Unless
>>> we can fix it, of course. The alternative is to apply Miao Xie's
>>> workaround patch temporarily.)
>>
>> If we were going to mark anything as broken, wouldn't cpu-hotplug be
>> the more appropriate victim? I suspect that there are more systems
>> using cpusets in production environments than using cpu hotplug. But
>> as you say, fixing it sounds better.
>
> I'm sorry for the harsh characterization and suggestion; please accept
> my apology. It was purely a result of my excitement at having made
> some progress in this case.
>
> But I have more good news; reverting this:
>
> commit f18f982abf183e91f435990d337164c7a43d1e6d
> Author: Max Krasnyansky <maxk@qualcomm.com>
> Date: Thu May 29 11:17:01 2008 -0700
>
> sched: CPU hotplug events must not destroy scheduler domains created by the
> cpusets

Does the patch below help?

(non-white-space-damaged version is attached)

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 9fceb97..ae61dc9 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1912,11 +1912,21 @@ static void common_cpu_mem_hotplug_unplug(void)
static int cpuset_handle_cpuhp(struct notifier_block *unused_nb,
unsigned long phase, void *unused_cpu)
{
- if (phase == CPU_DYING || phase == CPU_DYING_FROZEN)
+ swicth (phase) {
+ case CPU_UP_CANCELED:
+ case CPU_UP_CANCELED_FROZEN:
+ case CPU_DOWN_FAILED:
+ case CPU_DOWN_FAILED_FROZEN:
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ common_cpu_mem_hotplug_unplug();
+ break;
+ default:
return NOTIFY_DONE;

- common_cpu_mem_hotplug_unplug();
- return 0;
+ return NOTIFY_OK;
}

#ifdef CONFIG_MEMORY_HOTPLU


--
Best regards,
Dmitry Adamushko
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 9fceb97..ae61dc9 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1912,11 +1912,21 @@ static void common_cpu_mem_hotplug_unplug(void)
static int cpuset_handle_cpuhp(struct notifier_block *unused_nb,
unsigned long phase, void *unused_cpu)
{
- if (phase == CPU_DYING || phase == CPU_DYING_FROZEN)
+ swicth (phase) {
+ case CPU_UP_CANCELED:
+ case CPU_UP_CANCELED_FROZEN:
+ case CPU_DOWN_FAILED:
+ case CPU_DOWN_FAILED_FROZEN:
+ case CPU_ONLINE:
+ case CPU_ONLINE_FROZEN:
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ common_cpu_mem_hotplug_unplug();
+ break;
+ default:
return NOTIFY_DONE;

- common_cpu_mem_hotplug_unplug();
- return 0;
+ return NOTIFY_OK;
}

#ifdef CONFIG_MEMORY_HOTPLUG
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