If the smpboot_register_percpu_thread() is called after smpboot_create_threads() but before __cpu_up(), the smpboot thread of the online-ing CPU is not created, and it results a bug. So we use get_online_cpus() to prevent it.
smpboot_unregister_percpu_thread() travels all possible CPU, it doesn't need get_online_cpus() which is removed in the patch. CC: Thomas Gleixner <[email protected]> Cc: Rusty Russell <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Srivatsa S. Bhat <[email protected]> CC: [email protected] Signed-off-by: Lai Jiangshan <[email protected]> --- kernel/smpboot.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/smpboot.c b/kernel/smpboot.c index eb89e18..8adab87 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -279,6 +279,7 @@ int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread) unsigned int cpu; int ret = 0; + get_online_cpus(); mutex_lock(&smpboot_threads_lock); for_each_online_cpu(cpu) { ret = __smpboot_create_thread(plug_thread, cpu); @@ -291,6 +292,7 @@ int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread) list_add(&plug_thread->list, &hotplug_threads); out: mutex_unlock(&smpboot_threads_lock); + put_online_cpus(); return ret; } EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread); @@ -303,11 +305,9 @@ EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread); */ void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread) { - get_online_cpus(); mutex_lock(&smpboot_threads_lock); list_del(&plug_thread->list); smpboot_destroy_threads(plug_thread); mutex_unlock(&smpboot_threads_lock); - put_online_cpus(); } EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread); -- 1.7.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
