From 9ea09af3bd3090e8349ca2899ca2011bd94cda85 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 22 Dec 2008 12:36:30 +0100 Subject: stop_machine: introduce stop_machine_create/destroy. Introduce stop_machine_create/destroy. With this interface subsystems that need a non-failing stop_machine environment can create the stop_machine machine threads before actually calling stop_machine. When the threads aren't needed anymore they can be killed with stop_machine_destroy again. When stop_machine gets called and the threads aren't present they will be created and destroyed automatically. This restores the old behaviour of stop_machine. This patch also converts cpu hotplug to the new interface since it is special: cpu_down calls __stop_machine instead of stop_machine. However the kstop threads will only be created when stop_machine gets called. Changing the code so that the threads would be created automatically on __stop_machine is currently not possible: when __stop_machine gets called we hold cpu_add_remove_lock, which is the same lock that create_rt_workqueue would take. So the workqueue needs to be created before the cpu hotplug code locks cpu_add_remove_lock. Signed-off-by: Heiko Carstens Signed-off-by: Rusty Russell --- include/linux/stop_machine.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'include/linux/stop_machine.h') diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h index 74d59a641362..baba3a23a814 100644 --- a/include/linux/stop_machine.h +++ b/include/linux/stop_machine.h @@ -35,6 +35,24 @@ int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus); * won't come or go while it's being called. Used by hotplug cpu. */ int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus); + +/** + * stop_machine_create: create all stop_machine threads + * + * Description: This causes all stop_machine threads to be created before + * stop_machine actually gets called. This can be used by subsystems that + * need a non failing stop_machine infrastructure. + */ +int stop_machine_create(void); + +/** + * stop_machine_destroy: destroy all stop_machine threads + * + * Description: This causes all stop_machine threads which were created with + * stop_machine_create to be destroyed again. + */ +void stop_machine_destroy(void); + #else static inline int stop_machine(int (*fn)(void *), void *data, @@ -46,5 +64,9 @@ static inline int stop_machine(int (*fn)(void *), void *data, local_irq_enable(); return ret; } + +static inline int stop_machine_create(void) { return 0; } +static inline void stop_machine_destroy(void) { } + #endif /* CONFIG_SMP */ #endif /* _LINUX_STOP_MACHINE */ -- cgit