PM: Add suspend and hibernate notifications for after freeze

Suspend and hibernate notifications are available specifically when
the sequence starts and finishes.  However there are no notifications
during the process when tasks have been frozen.

Introduce two new events `PM_SUSPEND_POST_FREEZE` and
`PM_HIBERNATE_POST_FREEZE` that drivers can subscribe to and take
different actions specifically knowing userspace is frozen.

Suggested-by: Alex Deucher <[email protected]>
Signed-off-by: Mario Limonciello <[email protected]>

Author: superm1

Documentation/driver-api/pm/notifiers.rst

@@ -32,6 +32,18 @@ will be called upon the following events by the PM core:
 	additional work is done between the notifiers and the invocation of PM
 	callbacks for the "freeze" transition.
 
+``PM_HIBERNATION_POST_FREEZE``
+	The system is going to hibernate and tasks have just been frozen.
+
+``PM_SUSPEND_PREPARE``
+	The system is going to suspend, tasks will be frozen immediately.  This
+	is different from ``PM_HIBERNATION_PREPARE`` above, because in this case
+	additional work is done between the notifiers and the invocation of PM
+	callbacks for the "freeze" transition.
+
+``PM_SUSPEND_POST_FREEZE``
+	The system is going to suspend and tasks have just been frozen.
+
 ``PM_POST_HIBERNATION``
 	The system memory state has been restored from a hibernation image or an
 	error occurred during hibernation.  Device restore callbacks have been
@@ -54,9 +66,10 @@ will be called upon the following events by the PM core:
 	resume callbacks have been executed and tasks have been thawed.
 
 It is generally assumed that whatever the notifiers do for
-``PM_HIBERNATION_PREPARE``, should be undone for ``PM_POST_HIBERNATION``.
-Analogously, operations carried out for ``PM_SUSPEND_PREPARE`` should be
-reversed for ``PM_POST_SUSPEND``.
+``PM_HIBERNATION_PREPARE`` and ``PM_HIBERNATION_POST_FREEZE``, should be undone
+for ``PM_POST_HIBERNATION``.
+Analogously, operations carried out for ``PM_SUSPEND_PREPARE`` and ``PM_SUSPEND_POST_FREEZE``
+should be reversed for ``PM_POST_SUSPEND``.
 
 Moreover, if one of the notifiers fails for the ``PM_HIBERNATION_PREPARE`` or
 ``PM_SUSPEND_PREPARE`` event, the notifiers that have already succeeded for that

include/linux/suspend.h

@@ -438,12 +438,14 @@ static inline int is_hibernate_resume_dev(dev_t dev) { return 0; }
 #endif
 
 /* Hibernation and suspend events */
-#define PM_HIBERNATION_PREPARE	0x0001 /* Going to hibernate */
-#define PM_POST_HIBERNATION	0x0002 /* Hibernation finished */
-#define PM_SUSPEND_PREPARE	0x0003 /* Going to suspend the system */
-#define PM_POST_SUSPEND		0x0004 /* Suspend finished */
-#define PM_RESTORE_PREPARE	0x0005 /* Going to restore a saved image */
-#define PM_POST_RESTORE		0x0006 /* Restore failed */
+#define PM_HIBERNATION_PREPARE		0x0001 /* Going to hibernate */
+#define PM_HIBERNATION_POST_FREEZE	0x0002 /* Prepared for hibernation and tasks have been frozen */
+#define PM_POST_HIBERNATION		0x0003 /* Hibernation finished */
+#define PM_SUSPEND_PREPARE		0x0004 /* Going to suspend the system */
+#define PM_SUSPEND_POST_FREEZE		0x0005 /* Prepared and tasks have been frozen */
+#define PM_POST_SUSPEND			0x0006 /* Suspend finished */
+#define PM_RESTORE_PREPARE		0x0007 /* Going to restore a saved image */
+#define PM_POST_RESTORE			0x0008 /* Restore failed */
 
 extern struct mutex system_transition_mutex;
 

kernel/power/hibernate.c

@@ -793,11 +793,15 @@ int hibernate(void)
 	if (error)
 		goto Exit;
 
+	error = pm_notifier_call_chain_robust(PM_HIBERNATION_POST_FREEZE, PM_POST_HIBERNATION);
+	if (error)
+		goto Thaw;
+
 	lock_device_hotplug();
 	/* Allocate memory management structures */
 	error = create_basic_memory_bitmaps();
 	if (error)
-		goto Thaw;
+		goto Unlock_hotplug;
 
 	error = hibernation_snapshot(hibernation_mode == HIBERNATION_PLATFORM);
 	if (error || freezer_test_done)
@@ -845,8 +849,9 @@ int hibernate(void)
 
  Free_bitmaps:
 	free_basic_memory_bitmaps();
- Thaw:
+ Unlock_hotplug:
 	unlock_device_hotplug();
+ Thaw:
 	if (snapshot_test) {
 		pm_pr_dbg("Checking hibernation image\n");
 		error = swsusp_check(false);

kernel/power/suspend.c

@@ -531,13 +531,18 @@ static int suspend_prepare(suspend_state_t state)
 	trace_suspend_resume(TPS("freeze_processes"), 0, true);
 	error = suspend_freeze_processes();
 	trace_suspend_resume(TPS("freeze_processes"), 0, false);
-	if (!error)
-		return 0;
+	if (error)
+		goto Restore;
+	error = pm_notifier_call_chain_robust(PM_SUSPEND_POST_FREEZE, PM_POST_SUSPEND);
+	if (error)
+		goto Thaw;
 
-	dpm_save_failed_step(SUSPEND_FREEZE);
-	pm_notifier_call_chain(PM_POST_SUSPEND);
+	return 0;
+ Thaw:
+	suspend_thaw_processes();
  Restore:
 	pm_restore_console();
+	dpm_save_failed_step(SUSPEND_FREEZE);
 	return error;
 }