From: Nathan Lynch On some systems it can take a hotplugged cpu much longer to come up than it would at boot. If the cpu comes up after we've given up on it, it tends to die in its first attempt to kmem_cache_alloc (uninitialized percpu data, I imagine). In my experimentation I haven't seen a processor take more than one second to become available; the patch waits five seconds just to be safe. Signed-off-by: Nathan Lynch Signed-off-by: Andrew Morton --- 25-akpm/arch/ppc64/kernel/smp.c | 16 ++++++++++++++-- 1 files changed, 14 insertions(+), 2 deletions(-) diff -puN arch/ppc64/kernel/smp.c~ppc64-gives-up-too-quickly-on-hotplugged-cpu arch/ppc64/kernel/smp.c --- 25/arch/ppc64/kernel/smp.c~ppc64-gives-up-too-quickly-on-hotplugged-cpu Wed Jun 2 16:15:43 2004 +++ 25-akpm/arch/ppc64/kernel/smp.c Wed Jun 2 16:15:43 2004 @@ -912,8 +912,20 @@ int __devinit __cpu_up(unsigned int cpu) * use this value that I found through experimentation. * -- Cort */ - for (c = 5000; c && !cpu_callin_map[cpu]; c--) - udelay(100); + if (system_state == SYSTEM_BOOTING) + for (c = 5000; c && !cpu_callin_map[cpu]; c--) + udelay(100); +#ifdef CONFIG_HOTPLUG_CPU + else + /* + * CPUs can take much longer to come up in the + * hotplug case. Wait five seconds. + */ + for (c = 25; c && !cpu_callin_map[cpu]; c--) { + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_timeout(HZ/5); + } +#endif if (!cpu_callin_map[cpu]) { printk("Processor %u is stuck.\n", cpu); _