[PATCH] clean up lock_cpu_hotplug() in cpufreq
There are some callers in cpufreq hotplug notify path that the lowest
function calls lock_cpu_hotplug(). The lock is already held during
cpu_up() and cpu_down() calls when the notify calls are broadcast to
registered clients.
Ideally if possible, we could disable_preempt() at the highest caller and
make sure we dont sleep in the path down in cpufreq->driver_target() calls
but the calls are so intertwined and cumbersome to cleanup.
Hence we consistently use lock_cpu_hotplug() and unlock_cpu_hotplug() in
all places.
- Removed export of cpucontrol semaphore and made it static.
- removed explicit uses of up/down with lock_cpu_hotplug()
so we can keep track of the the callers in same thread context and
just keep refcounts without calling a down() that causes a deadlock.
- Removed current_in_hotplug() uses
- Removed PF_HOTPLUG_CPU in sched.h introduced for the current_in_hotplug()
temporary workaround.
Tested with insmod of cpufreq_stat.ko, and logical online/offline
to make sure we dont have any hang situations.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Cc: Zwane Mwaikambo <zwane@linuxpower.ca>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 43c4453..0ed1d48 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -65,10 +65,9 @@
#ifdef CONFIG_HOTPLUG_CPU
/* Stop CPUs going up and down. */
-extern struct semaphore cpucontrol;
-#define lock_cpu_hotplug() down(&cpucontrol)
-#define unlock_cpu_hotplug() up(&cpucontrol)
-#define lock_cpu_hotplug_interruptible() down_interruptible(&cpucontrol)
+extern void lock_cpu_hotplug(void);
+extern void unlock_cpu_hotplug(void);
+extern int lock_cpu_hotplug_interruptible(void);
#define hotcpu_notifier(fn, pri) { \
static struct notifier_block fn##_nb = \
{ .notifier_call = fn, .priority = pri }; \