PM / reboot: Eliminate race between reboot and suspend

At present, "systemctl suspend" and "shutdown" can run in parrallel. A
system can suspend after devices_shutdown(), and resume. Then the shutdown
task goes on to power off. This causes many devices are not really shut
off. Hence replacing reboot_mutex with system_transition_mutex (renamed
from pm_mutex) to achieve the exclusion. The renaming of pm_mutex as
system_transition_mutex can be better to reflect the purpose of the mutex.

Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

6 files changed, 24 insertions, 21 deletions

diff --git a/kernel/freezer.c b/kernel/freezer.c
index 6f56a9e219fa..b162b74611e4 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -15,7 +15,9 @@
 atomic_t system_freezing_cnt = ATOMIC_INIT(0);
 EXPORT_SYMBOL(system_freezing_cnt);
 
-/* indicate whether PM freezing is in effect, protected by pm_mutex */
+/* indicate whether PM freezing is in effect, protected by
+ * system_transition_mutex
+ */
 bool pm_freezing;
 bool pm_nosig_freezing;
 
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 38f3f96b4b12..abef759de7c8 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -338,7 +338,7 @@ static int create_image(int platform_mode)
  * hibernation_snapshot - Quiesce devices and create a hibernation image.
  * @platform_mode: If set, use platform driver to prepare for the transition.
  *
- * This routine must be called with pm_mutex held.
+ * This routine must be called with system_transition_mutex held.
  */
 int hibernation_snapshot(int platform_mode)
 {
@@ -500,8 +500,9 @@ static int resume_target_kernel(bool platform_mode)
  * hibernation_restore - Quiesce devices and restore from a hibernation image.
  * @platform_mode: If set, use platform driver to prepare for the transition.
  *
- * This routine must be called with pm_mutex held.  If it is successful, control
- * reappears in the restored target kernel in hibernation_snapshot().
+ * This routine must be called with system_transition_mutex held.  If it is
+ * successful, control reappears in the restored target kernel in
+ * hibernation_snapshot().
  */
 int hibernation_restore(int platform_mode)
 {
@@ -806,13 +807,13 @@ static int software_resume(void)
 	 * name_to_dev_t() below takes a sysfs buffer mutex when sysfs
 	 * is configured into the kernel. Since the regular hibernate
 	 * trigger path is via sysfs which takes a buffer mutex before
-	 * calling hibernate functions (which take pm_mutex) this can
-	 * cause lockdep to complain about a possible ABBA deadlock
+	 * calling hibernate functions (which take system_transition_mutex)
+	 * this can cause lockdep to complain about a possible ABBA deadlock
 	 * which cannot happen since we're in the boot code here and
 	 * sysfs can't be invoked yet. Therefore, we use a subclass
 	 * here to avoid lockdep complaining.
 	 */
-	mutex_lock_nested(&pm_mutex, SINGLE_DEPTH_NESTING);
+	mutex_lock_nested(&system_transition_mutex, SINGLE_DEPTH_NESTING);
 
 	if (swsusp_resume_device)
 		goto Check_image;
@@ -900,7 +901,7 @@ static int software_resume(void)
 	atomic_inc(&snapshot_device_available);
 	/* For success case, the suspend path will release the lock */
  Unlock:
-	mutex_unlock(&pm_mutex);
+	mutex_unlock(&system_transition_mutex);
 	pm_pr_dbg("Hibernation image not present or could not be loaded.\n");
 	return error;
  Close_Finish:
diff --git a/kernel/power/main.c b/kernel/power/main.c
index d9706da10930..35b50823d83b 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -15,17 +15,16 @@
 #include <linux/workqueue.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
+#include <linux/suspend.h>
 
 #include "power.h"
 
-DEFINE_MUTEX(pm_mutex);
-
 #ifdef CONFIG_PM_SLEEP
 
 void lock_system_sleep(void)
 {
 	current->flags |= PF_FREEZER_SKIP;
-	mutex_lock(&pm_mutex);
+	mutex_lock(&system_transition_mutex);
 }
 EXPORT_SYMBOL_GPL(lock_system_sleep);
 
@@ -37,8 +36,9 @@ void unlock_system_sleep(void)
 	 *
 	 * Reason:
 	 * Fundamentally, we just don't need it, because freezing condition
-	 * doesn't come into effect until we release the pm_mutex lock,
-	 * since the freezer always works with pm_mutex held.
+	 * doesn't come into effect until we release the
+	 * system_transition_mutex lock, since the freezer always works with
+	 * system_transition_mutex held.
 	 *
 	 * More importantly, in the case of hibernation,
 	 * unlock_system_sleep() gets called in snapshot_read() and
@@ -47,7 +47,7 @@ void unlock_system_sleep(void)
 	 * enter the refrigerator, thus causing hibernation to lockup.
 	 */
 	current->flags &= ~PF_FREEZER_SKIP;
-	mutex_unlock(&pm_mutex);
+	mutex_unlock(&system_transition_mutex);
 }
 EXPORT_SYMBOL_GPL(unlock_system_sleep);
 
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 87331565e505..9e13afe65a14 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -556,7 +556,7 @@ static int enter_state(suspend_state_t state)
 	} else if (!valid_state(state)) {
 		return -EINVAL;
 	}
-	if (!mutex_trylock(&pm_mutex))
+	if (!mutex_trylock(&system_transition_mutex))
 		return -EBUSY;
 
 	if (state == PM_SUSPEND_TO_IDLE)
@@ -590,7 +590,7 @@ static int enter_state(suspend_state_t state)
 	pm_pr_dbg("Finishing wakeup.\n");
 	suspend_finish();
  Unlock:
-	mutex_unlock(&pm_mutex);
+	mutex_unlock(&system_transition_mutex);
 	return error;
 }
 
diff --git a/kernel/power/user.c b/kernel/power/user.c
index abd225550271..2d8b60a3c86b 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -216,7 +216,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
 
-	if (!mutex_trylock(&pm_mutex))
+	if (!mutex_trylock(&system_transition_mutex))
 		return -EBUSY;
 
 	lock_device_hotplug();
@@ -394,7 +394,7 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
 	}
 
 	unlock_device_hotplug();
-	mutex_unlock(&pm_mutex);
+	mutex_unlock(&system_transition_mutex);
 
 	return error;
 }
diff --git a/kernel/reboot.c b/kernel/reboot.c
index e4ced883d8de..8fb44dec9ad7 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -294,7 +294,7 @@ void kernel_power_off(void)
 }
 EXPORT_SYMBOL_GPL(kernel_power_off);
 
-static DEFINE_MUTEX(reboot_mutex);
+DEFINE_MUTEX(system_transition_mutex);
 
 /*
  * Reboot system call: for obvious reasons only root may call it,
@@ -338,7 +338,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
 		cmd = LINUX_REBOOT_CMD_HALT;
 
-	mutex_lock(&reboot_mutex);
+	mutex_lock(&system_transition_mutex);
 	switch (cmd) {
 	case LINUX_REBOOT_CMD_RESTART:
 		kernel_restart(NULL);
@@ -389,7 +389,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 		ret = -EINVAL;
 		break;
 	}
-	mutex_unlock(&reboot_mutex);
+	mutex_unlock(&system_transition_mutex);
 	return ret;
 }