Messages in this thread Patch in this message | | | Date | Tue, 31 May 2005 01:00:31 -0700 | From | Ashok Raj <> | Subject | Re: [PATCH]CPU hotplug breaks wake_up_new_task |
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On Tue, May 31, 2005 at 12:35:09AM -0700, Shaohua Li wrote: > > Hi, > There is a race condition at wake_up_new_task at CPU hotplug case. > Say do_fork > copy_process (which sets new forked task's current cpu, > cpu_allowed) > <-------- the new forked task's current cpu is offline > wake_up_new_task > wake_up_new_task will put the forked task into a dead cpu. > > Thanks, > Shaohua > > Signed-off-by: Shaohua Li<shaohua.li@intel.com> > --- > > linux-2.6.11-rc5-mm1-root/kernel/sched.c | 25 .... Deleted.... > /* > * wake_up_new_task - wake up a newly created task for the first > time. > * > @@ -1426,9 +1430,20 @@ void fastcall wake_up_new_task(task_t * > runqueue_t *rq, *this_rq; > > rq = task_rq_lock(p, &flags); > - BUG_ON(p->state != TASK_RUNNING); > this_cpu = smp_processor_id(); > cpu = task_cpu(p); > +#ifdef CONFIG_HOTPLUG_CPU > + while (!cpu_online(cpu)) { > + cpu = task_select_online_cpu(cpu, p); > + set_task_cpu(p, cpu); > + task_rq_unlock(rq, &flags); > + /* CPU hotplug might occur here */ > + rq = task_rq_lock(p, &flags); > + this_cpu = smp_processor_id(); > + cpu = task_cpu(p); > + } > +#endif
The while() loop doesnt look pretty here.. could you try to disable preempt, and see the problem goes away? or use get_cpu()/put_cpu() combo when you get this_cpu?
Just wondering if the code would be a little more simpler in this case.
Nick should have something to say ...
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