From 90d45d17f3e68608ac7ba8fc3d7acce022a19c8e Mon Sep 17 00:00:00 2001 From: Ashok Raj Date: Tue, 8 Nov 2005 21:34:24 -0800 Subject: [PATCH] cpu hotplug: fix locking in cpufreq drivers When calling target drivers to set frequency, we take cpucontrol lock. When we modified the code to accomodate CPU hotplug, there was an attempt to take a double lock of cpucontrol leading to a deadlock. Since the current thread context is already holding the cpucontrol lock, we dont need to make another attempt to acquire it. Now we leave a trace in current->flags indicating current thread already is under cpucontrol lock held, so we dont attempt to do this another time. Thanks to Andrew Morton for the beating:-) From: Brice Goglin Build fix (akpm: this patch is still unpleasant. Ashok continues to look for a cleaner solution, doesn't he? ;)) Signed-off-by: Ashok Raj Signed-off-by: Brice Goglin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/cpu.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/cpu.h') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 1f7b2c097503..43c44530ef9d 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -42,6 +42,7 @@ struct notifier_block; /* Need to know about CPUs going up/down? */ extern int register_cpu_notifier(struct notifier_block *nb); extern void unregister_cpu_notifier(struct notifier_block *nb); +extern int current_in_cpu_hotplug(void); int cpu_up(unsigned int cpu); @@ -54,6 +55,10 @@ static inline int register_cpu_notifier(struct notifier_block *nb) static inline void unregister_cpu_notifier(struct notifier_block *nb) { } +static inline int current_in_cpu_hotplug(void) +{ + return 0; +} #endif /* CONFIG_SMP */ extern struct sysdev_class cpu_sysdev_class; -- cgit v1.2.1