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>

2 files changed, 6 insertions, 0 deletions

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index d4e54053d009..0b78f72ad39d 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -652,6 +652,7 @@ int hibernate(void)
         if (error)
                 goto Exit;
 
+        lock_device_hotplug();
         /* Allocate memory management structures */
         error = create_basic_memory_bitmaps();
         if (error)
@@ -685,6 +686,7 @@ int hibernate(void)
  Free_bitmaps:
         free_basic_memory_bitmaps();
  Thaw:
+        unlock_device_hotplug();
         thaw_processes();
 
         /* Don't bother checking whether freezer_test_done is true */
@@ -814,6 +816,7 @@ static int software_resume(void)
 
         pr_debug("PM: Loading hibernation image.\n");
 
+        lock_device_hotplug();
         error = create_basic_memory_bitmaps();
         if (error)
                 goto Thaw;
@@ -827,6 +830,7 @@ static int software_resume(void)
         swsusp_free();
         free_basic_memory_bitmaps();
  Thaw:
+        unlock_device_hotplug();
         thaw_processes();
  Finish:
         pm_notifier_call_chain(PM_POST_RESTORE);
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 63368163e98d..72e8f4fd616d 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;