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On Sun, 2003-03-09 at 19:03, Zwane Mwaikambo wrote: > > cpu = smp_processor_id(); > > /* do not want to preempt here, but we can! */ > > preempt_disable(); > > _raw_read_lock(&__brlock_array[cpu][idx]); > > How are we able to preempt there? Timer tick? Yep. Any interrupt, actually. Or the reschedule IPI on SMP systems. Kernel preemption off an interrupt is actually the most common (and the ideal) place to preempt since an interrupt is usually what wakes up a task off I/O and sets need_resched. So kernel preemption lets us reschedule the higher priority task the moment the interrupt wakes it up. Of course, if a lock is held, we have to wait till we drop it. Robert Love - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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