PM / hibernate / memory hotplug: Rework mutual exclusion

Since all of the memory hotplug operations have to be carried out
under device_hotplug_lock, they won't need to acquire pm_mutex if
device_hotplug_lock is held around hibernation.

For this reason, make the hibernation code acquire
device_hotplug_lock after freezing user space processes and
release it before thawing them.  At the same tim drop the
lock_system_sleep() and unlock_system_sleep() calls from
lock_memory_hotplug() and unlock_memory_hotplug(), respectively.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Toshi Kani <toshi.kani@hp.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/power/user.c b/kernel/power/user.c
index 6336816..72e8f4f 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -201,6 +201,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 	if (!mutex_trylock(&pm_mutex))
 		return -EBUSY;
 
+	lock_device_hotplug();
 	data = filp->private_data;
 
 	switch (cmd) {
@@ -373,6 +374,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 
 	}
 
+	unlock_device_hotplug();
 	mutex_unlock(&pm_mutex);
 
 	return error;