On 8/29/2012 4:53 PM, Russell King - ARM Linux wrote: > On Tue, Aug 21, 2012 at 09:03:49PM -0700, Stephen Boyd wrote: >> Nothing stops a process from hotplugging in a CPU concurrently >> with a sys_reboot() call. In such a situation we could have >> ipi_cpu_stop() mark a cpu as 'offline' and _cpu_up() ignore the >> fact that the CPU is not really offline and call the >> CPU_UP_PREPARE notifier. When this happens stop_machine code will >> complain that the cpu thread already exists and BUG_ON(). > This puts us at odds with x86, which is a bad thing without first > investigating whether a generic solution which fixes all arches would > be more appropriate.
I went this way because it seems that we stop CPUs in architecture specific code instead of doing it generically (although we have smp_send_stop()?). It would be nice if we could generalize the cpu stopping code so that reboot at the architectual level doesn't have to do this. > > A better solution may be to mark those CPUs as being not-present, > which will prevent them being hot-plugged back. That sounds fine to me. I can s/active/present/ for v2 if we can get some kind of consensus. I was also thinking we could stop using these functions entirely and have some private stopped CPUs map that we check instead. -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- 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/
