On 12/10/2012 01:18 AM, Oleg Nesterov wrote: > On 12/07, Srivatsa S. Bhat wrote: >> >> Once stop_machine() is gone from the CPU offline path, we won't be able to >> depend on local_irq_save() to prevent CPUs from going offline from under us. > > OK, I guess we need to avoid resched_task()->smp_send_reschedule() > after __cpu_disable() and before migrate_tasks(). >
Yes. > But, whatever problem we have, > >> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline, >> while invoking from atomic context. > > it should be solved, so... > >> - if (preempt && rq != p_rq) >> + if (preempt && rq != p_rq && cpu_online(task_cpu(p))) > > Why do we need this change? > > Afaics, you could add BUG_ON(!cpu_online(...)) instead? > > I am just curious. > Oh, I think that's a remnant of v1 (which needed readers to use cpu_online_stable()). You're right, we don't need it. Or we could put a BUG_ON instead, like you suggested. Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
