[PATCH 2/2] x86, cpu hotplug: Fix cpu bringup concurrency issue
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From: Borislav Petkov on 4 Aug 2010 12:50 From: Borislav Petkov <borislav.petkov(a)amd.com> When testing cpu hotplug code on 32-bit we kept hitting the "CPU%d: Stuck ??" message due to multiple cores concurrently accessing the cpu_callin_mask, among others. Since these codepaths are not protected from concurrent access due to the fact that there's no sane reason for making an already complex code unnecessarily more complex - we hit the issue only when insanely switching cores off- and online - serialize hotplugging cores on the sysfs level and be done with it. Cc: <stable(a)kernel.org> Signed-off-by: Borislav Petkov <borislav.petkov(a)amd.com> --- arch/x86/Kconfig | 6 ++++++ arch/x86/kernel/smpboot.c | 19 +++++++++++++++++++ 2 files changed, 25 insertions(+), 0 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index dcb0593..1598663 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -58,6 +58,7 @@ config X86 select ANON_INODES select HAVE_ARCH_KMEMCHECK select HAVE_USER_RETURN_NOTIFIER + select ARCH_CPU_PROBE_RELEASE config INSTRUCTION_DECODER def_bool (KPROBES || PERF_EVENTS) @@ -247,6 +248,11 @@ config ARCH_HWEIGHT_CFLAGS config KTIME_SCALAR def_bool X86_32 + +config ARCH_CPU_PROBE_RELEASE + def_bool y + depends on HOTPLUG_CPU + source "init/Kconfig" source "kernel/Kconfig.freezer" diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 6859a42..9e8e61b 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -90,6 +90,25 @@ DEFINE_PER_CPU(int, cpu_state) = { 0 }; static DEFINE_PER_CPU(struct task_struct *, idle_thread_array); #define get_idle_for_cpu(x) (per_cpu(idle_thread_array, x)) #define set_idle_for_cpu(x, p) (per_cpu(idle_thread_array, x) = (p)) + +/* + * We need this for trampoline_base protection from concurrent accesses when + * off- and onlining cores wildly. + */ +static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex); + +void cpu_hotplug_driver_lock() +{ + mutex_lock(&x86_cpu_hotplug_driver_mutex); +} + +void cpu_hotplug_driver_unlock() +{ + mutex_unlock(&x86_cpu_hotplug_driver_mutex); +} + +ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; } +ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; } #else static struct task_struct *idle_thread_array[NR_CPUS] __cpuinitdata ; #define get_idle_for_cpu(x) (idle_thread_array[(x)]) -- 1.6.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |