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http://bugzilla.kernel.org/show_bug.cgi?id=5203 There is a small race during SMP shutdown between the processor issuing the shutdown and the other processors clearing themselves off the cpu_online_map as they do this without using the normal cpu offline synchronisation. To avoid this we should wait for all the other processors to clear their corresponding bits and then proceed. This way we can safely make the cpu_online test in smp_send_reschedule, it's safe during normal runtime as smp_send_reschedule is called with a lock held / preemption disabled. Signed-off-by: Zwane Mwaikambo <zwane@arm.linux.org.uk> arch/i386/kernel/smp.c | 12 +++++++++--- arch/x86_64/kernel/smp.c | 12 +++++++++++- 2 files changed, 20 insertions(+), 4 deletions(-) diff -r 2c0d5afbfb94 arch/i386/kernel/smp.c --- a/arch/i386/kernel/smp.c Fri Nov 25 17:42:19 2005 +++ b/arch/i386/kernel/smp.c Sun Nov 27 02:00:59 2005 @@ -164,7 +164,6 @@ unsigned long flags; local_irq_save(flags); - WARN_ON(mask & ~cpus_addr(cpu_online_map)[0]); /* * Wait for idle. */ @@ -476,8 +475,8 @@ */ void smp_send_reschedule(int cpu) { - WARN_ON(cpu_is_offline(cpu)); - send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR); + if (likely(cpu_online(cpu))) + send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR); } /* @@ -585,7 +584,14 @@ void smp_send_stop(void) { + cpumask_t mask; + + mask = cpumask_of_cpu(smp_processor_id()); smp_call_function(stop_this_cpu, NULL, 1, 0); + + /* Wait for other cpus to halt */ + while (!cpus_equal(mask, cpu_online_map)) + cpu_relax(); local_irq_disable(); disable_local_APIC(); diff -r 2c0d5afbfb94 arch/x86_64/kernel/smp.c --- a/arch/x86_64/kernel/smp.c Fri Nov 25 17:42:19 2005 +++ b/arch/x86_64/kernel/smp.c Sun Nov 27 02:00:59 2005 @@ -293,7 +293,8 @@ void smp_send_reschedule(int cpu) { - send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR); + if (likely(cpu_online(cpu))) + send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR); } /* @@ -470,6 +471,8 @@ void smp_send_stop(void) { int nolock = 0; + cpumask_t mask; + if (reboot_force) return; /* Don't deadlock on the call lock in panic */ @@ -477,7 +480,14 @@ /* ignore locking because we have paniced anyways */ nolock = 1; } + + mask = cpumask_of_cpu(smp_processor_id()); __smp_call_function(smp_really_stop_cpu, NULL, 0, 0); + + /* wait for the other cpus to halt */ + while (!cpus_equal(mask, cpu_online_map)) + cpu_relax(); + if (!nolock) spin_unlock(&call_lock); - 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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