From 3da1c84c00c7e5fa8348336bd8c342f9128b0f14 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 25 Jul 2008 01:47:50 -0700 Subject: workqueues: make get_online_cpus() useable for work->func() workqueue_cpu_callback(CPU_DEAD) flushes cwq->thread under cpu_maps_update_begin(). This means that the multithreaded workqueues can't use get_online_cpus() due to the possible deadlock, very bad and very old problem. Introduce the new state, CPU_POST_DEAD, which is called after cpu_hotplug_done() but before cpu_maps_update_done(). Change workqueue_cpu_callback() to use CPU_POST_DEAD instead of CPU_DEAD. This means that create/destroy functions can't rely on get_online_cpus() any longer and should take cpu_add_remove_lock instead. [akpm@linux-foundation.org: fix CONFIG_SMP=n] Signed-off-by: Oleg Nesterov Acked-by: Gautham R Shenoy Cc: Heiko Carstens Cc: Max Krasnyansky Cc: Paul Jackson Cc: Paul Menage Cc: Peter Zijlstra Cc: Vegard Nossum Cc: Martin Schwidefsky Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpu.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'include/linux/cpu.h') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 7464ba3b4333..d7faf8808497 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -69,10 +69,11 @@ static inline void unregister_cpu_notifier(struct notifier_block *nb) #endif int cpu_up(unsigned int cpu); - extern void cpu_hotplug_init(void); +extern void cpu_maps_update_begin(void); +extern void cpu_maps_update_done(void); -#else +#else /* CONFIG_SMP */ static inline int register_cpu_notifier(struct notifier_block *nb) { @@ -87,10 +88,16 @@ static inline void cpu_hotplug_init(void) { } +static inline void cpu_maps_update_begin(void) +{ +} + +static inline void cpu_maps_update_done(void) +{ +} + #endif /* CONFIG_SMP */ extern struct sysdev_class cpu_sysdev_class; -extern void cpu_maps_update_begin(void); -extern void cpu_maps_update_done(void); #ifdef CONFIG_HOTPLUG_CPU /* Stop CPUs going up and down. */ -- cgit v1.2.3