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Date: Thu, 10 Jul 2008 00:32:40 +0200 From: Dmitry Adamushko <dmitry.adamushko@...il.com> To: Ingo Molnar <mingo@...e.hu> Cc: miaox@...fujitsu.com, Lai Jiangshan <laijs@...fujitsu.com>, Ingo Molnar <mingo@...e.hu>, Heiko Carstens <heiko.carstens@...ibm.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Avi Kivity <avi@...ranet.com>, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [BUG] CFS vs cpu hotplug hm, while looking at this code again... Ingo, I think we may have a race between try_to_wake_up() and migrate_live_tasks() -> move_task_off_dead_cpu() when the later one may end up looping endlessly. Subject: sched: prevent a potentially endless loop in move_task_off_dead_cpu() Interrupts are enabled on other CPUs when migration_call(CPU_DEAD, ...) is called so we may get a race between try_to_wake_up() and migrate_live_tasks() -> move_task_off_dead_cpu(). The former one may push a task out of a dead CPU causing the later one to loop endlessly. Signed-off-by: Dmitry Adamushko <dmitry.adamushko@...il.com> --- diff --git a/kernel/sched.c b/kernel/sched.c index 94ead43..9397b87 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5621,8 +5621,10 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) double_rq_lock(rq_src, rq_dest); /* Already moved. */ - if (task_cpu(p) != src_cpu) + if (task_cpu(p) != src_cpu) { + ret = 1; goto out; + } /* Affinity changed (again). */ if (!cpu_isset(dest_cpu, p->cpus_allowed)) goto out; --- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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