PM: Do not hold dpm_list_mtx while disabling/enabling nonboot CPUs

We shouldn't hold dpm_list_mtx while executing
[disable|enable]_nonboot_cpus(), because theoretically this may lead
to a deadlock as shown by the following example (provided by Johannes
Berg):

CPU 3       CPU 2                     CPU 1
                                      suspend/hibernate
            something:
            rtnl_lock()               device_pm_lock()
                                       -> mutex_lock(&dpm_list_mtx)

            mutex_lock(&dpm_list_mtx)

linkwatch_work
 -> rtnl_lock()
                                      disable_nonboot_cpus()
                                       -> flush CPU 3 workqueue

Fortunately, device drivers are supposed to stop any activities that
might lead to the registration of new device objects way before
disable_nonboot_cpus() is called, so it shouldn't be necessary to
hold dpm_list_mtx over the entire late part of device suspend and
early part of device resume.

Thus, during the late suspend and the early resume of devices acquire
dpm_list_mtx only when dpm_list is going to be traversed and release
it right after that.

This patch is reported to fix the regressions tracked as
http://bugzilla.kernel.org/show_bug.cgi?id=13245.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Miles Lane <miles.lane@gmail.com>
Tested-by: Ming Lei <tom.leiming@gmail.com>

2 files changed, 4 insertions, 24 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index b0dc9e7a0d17..5cb080e7eebd 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -215,8 +215,6 @@ static int create_image(int platform_mode)
         if (error)
                 return error;
 
-        device_pm_lock();
-
         /* At this point, device_suspend() has been called, but *not*
          * device_power_down(). We *must* call device_power_down() now.
          * Otherwise, drivers for some devices (e.g. interrupt controllers)
@@ -227,7 +225,7 @@ static int create_image(int platform_mode)
         if (error) {
                 printk(KERN_ERR "PM: Some devices failed to power down, "
                         "aborting hibernation\n");
-                goto Unlock;
+                return error;
         }
 
         error = platform_pre_snapshot(platform_mode);
@@ -280,9 +278,6 @@ static int create_image(int platform_mode)
         device_power_up(in_suspend ?
                 (error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
 
- Unlock:
-        device_pm_unlock();
-
         return error;
 }
 
@@ -344,13 +339,11 @@ static int resume_target_kernel(bool platform_mode)
 {
         int error;
 
-        device_pm_lock();
-
         error = device_power_down(PMSG_QUIESCE);
         if (error) {
                 printk(KERN_ERR "PM: Some devices failed to power down, "
                         "aborting resume\n");
-                goto Unlock;
+                return error;
         }
 
         error = platform_pre_restore(platform_mode);
@@ -403,9 +396,6 @@ static int resume_target_kernel(bool platform_mode)
 
         device_power_up(PMSG_RECOVER);
 
- Unlock:
-        device_pm_unlock();
-
         return error;
 }
 
@@ -464,11 +454,9 @@ int hibernation_platform_enter(void)
                 goto Resume_devices;
         }
 
-        device_pm_lock();
-
         error = device_power_down(PMSG_HIBERNATE);
         if (error)
-                goto Unlock;
+                goto Resume_devices;
 
         error = hibernation_ops->prepare();
         if (error)
@@ -493,9 +481,6 @@ int hibernation_platform_enter(void)
 
         device_power_up(PMSG_RESTORE);
 
- Unlock:
-        device_pm_unlock();
-
  Resume_devices:
         entering_platform_hibernation = false;
         device_resume(PMSG_RESTORE);
diff --git a/kernel/power/main.c b/kernel/power/main.c
index f99ed6a75eac..868028280d13 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -289,12 +289,10 @@ static int suspend_enter(suspend_state_t state)
 {
         int error;
 
-        device_pm_lock();
-
         if (suspend_ops->prepare) {
                 error = suspend_ops->prepare();
                 if (error)
-                        goto Done;
+                        return error;
         }
 
         error = device_power_down(PMSG_SUSPEND);
@@ -343,9 +341,6 @@ static int suspend_enter(suspend_state_t state)
         if (suspend_ops->finish)
                 suspend_ops->finish();
 
- Done:
-        device_pm_unlock();
-
         return error;
 }