From cdfb2881023413742e545893e1b84ba96135d8b8 Mon Sep 17 00:00:00 2001 From: Matt Evans Date: Mon, 7 Mar 2011 17:26:04 +0530 Subject: [PATCH] powerpc/kexec: Fix orphaned offline CPUs across kexec Commit: e8e5c2155b0035b6e04f29be67f6444bc914005b upstream When CPU hotplug is used, some CPUs may be offline at the time a kexec is performed. The subsequent kernel may expect these CPUs to be already running, and will declare them stuck. On pseries, there's also a soft-offline (cede) state that CPUs may be in; this can also cause problems as the kexeced kernel may ask RTAS if they're online -- and RTAS would say they are. The CPU will either appear stuck, or will cause a crash as we replace its cede loop beneath it. This patch kicks each present offline CPU awake before the kexec, so that none are forever lost to these assumptions in the subsequent kernel. Now, the behaviour is that all available CPUs that were offlined are now online & usable after the kexec. This mimics the behaviour of a full reboot (on which all CPUs will be restarted). Signed-off-by: Matt Evans Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Kamalesh babulal cc: Anton Blanchard Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/machine_kexec_64.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c index 040bd1de8d9..1a8de63489a 100644 --- a/arch/powerpc/kernel/machine_kexec_64.c +++ b/arch/powerpc/kernel/machine_kexec_64.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include @@ -169,10 +170,34 @@ static void kexec_smp_down(void *arg) /* NOTREACHED */ } +/* + * We need to make sure each present CPU is online. The next kernel will scan + * the device tree and assume primary threads are online and query secondary + * threads via RTAS to online them if required. If we don't online primary + * threads, they will be stuck. However, we also online secondary threads as we + * may be using 'cede offline'. In this case RTAS doesn't see the secondary + * threads as offline -- and again, these CPUs will be stuck. + * + * So, we online all CPUs that should be running, including secondary threads. + */ +static void wake_offline_cpus(void) +{ + int cpu = 0; + + for_each_present_cpu(cpu) { + if (!cpu_online(cpu)) { + printk(KERN_INFO "kexec: Waking offline cpu %d.\n", + cpu); + cpu_up(cpu); + } + } +} + static void kexec_prepare_cpus(void) { int my_cpu, i, notified=-1; + wake_offline_cpus(); smp_call_function(kexec_smp_down, NULL, /* wait */0); my_cpu = get_cpu(); -- 2.11.4.GIT