From 759846482a16335fca1bb2d94d35c30a5decc448 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Thu, 23 May 2013 10:36:51 +1000 Subject: [PATCH] CPU hotplug: provide a generic helper to disable/enable CPU hotplug There are instances in the kernel where we would like to disable CPU hotplug (from sysfs) during some important operation. Today the freezer code depends on this and the code to do it was kinda tailor-made for that. Restructure the code and make it generic enough to be useful for other usecases too. Signed-off-by: Srivatsa S. Bhat Signed-off-by: Robin Holt Cc: H. Peter Anvin Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Russ Anderson Cc: Robin Holt Cc: Russell King Cc: Guan Xuetao Cc: Shawn Guo Cc: Signed-off-by: Andrew Morton --- include/linux/cpu.h | 14 ++++++++++++++ kernel/cpu.c | 27 +++++++++------------------ 2 files changed, 23 insertions(+), 18 deletions(-) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index c6f6e0839b61..73f02a3e6ab7 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -168,6 +168,20 @@ static inline void cpu_maps_update_done(void) } #endif /* CONFIG_SMP */ + +#ifdef CONFIG_PM_SLEEP_SMP +extern void cpu_hotplug_enable(void); +extern void cpu_hotplug_disable(void); +#else +static inline void cpu_hotplug_enable(void) +{ +} + +static inline void cpu_hotplug_disable(void) +{ +} +#endif + extern struct bus_type cpu_subsys; #ifdef CONFIG_HOTPLUG_CPU diff --git a/kernel/cpu.c b/kernel/cpu.c index b5e4ab2d427e..28769f5ca9a4 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -541,29 +541,20 @@ static int __init alloc_frozen_cpus(void) core_initcall(alloc_frozen_cpus); /* - * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU - * hotplug when tasks are about to be frozen. Also, don't allow the freezer - * to continue until any currently running CPU hotplug operation gets - * completed. - * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the - * 'cpu_add_remove_lock'. And this same lock is also taken by the regular - * CPU hotplug path and released only after it is complete. Thus, we - * (and hence the freezer) will block here until any currently running CPU - * hotplug operation gets completed. + * Wait for currently running CPU hotplug operations to complete (if any) and + * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects + * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the + * hotplug path before performing hotplug operations. So acquiring that lock + * guarantees mutual exclusion from any currently running hotplug operations. */ -void cpu_hotplug_disable_before_freeze(void) +void cpu_hotplug_disable(void) { cpu_maps_update_begin(); cpu_hotplug_disabled = 1; cpu_maps_update_done(); } - -/* - * When tasks have been thawed, re-enable regular CPU hotplug (which had been - * disabled while beginning to freeze tasks). - */ -void cpu_hotplug_enable_after_thaw(void) +void cpu_hotplug_enable(void) { cpu_maps_update_begin(); cpu_hotplug_disabled = 0; @@ -589,12 +580,12 @@ cpu_hotplug_pm_callback(struct notifier_block *nb, case PM_SUSPEND_PREPARE: case PM_HIBERNATION_PREPARE: - cpu_hotplug_disable_before_freeze(); + cpu_hotplug_disable(); break; case PM_POST_SUSPEND: case PM_POST_HIBERNATION: - cpu_hotplug_enable_after_thaw(); + cpu_hotplug_enable(); break; default: -- 2.39.5