[PATCH 3/3] PM / hibernate / memory hotplug: Rework mutual exclusion

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

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@xxxxxxxxx>
---
 kernel/power/hibernate.c |    4 ++++
 kernel/power/user.c      |    2 ++
 mm/memory_hotplug.c      |    4 ----
 3 files changed, 6 insertions(+), 4 deletions(-)

Index: linux-pm/kernel/power/hibernate.c
===================================================================
--- linux-pm.orig/kernel/power/hibernate.c
+++ linux-pm/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);
Index: linux-pm/kernel/power/user.c
===================================================================
--- linux-pm.orig/kernel/power/user.c
+++ linux-pm/kernel/power/user.c
@@ -201,6 +201,7 @@ static long snapshot_ioctl(struct file *
 	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 *
 
 	}
 
+	unlock_device_hotplug();
 	mutex_unlock(&pm_mutex);
 
 	return error;
Index: linux-pm/mm/memory_hotplug.c
===================================================================
--- linux-pm.orig/mm/memory_hotplug.c
+++ linux-pm/mm/memory_hotplug.c
@@ -51,14 +51,10 @@ DEFINE_MUTEX(mem_hotplug_mutex);
 void lock_memory_hotplug(void)
 {
 	mutex_lock(&mem_hotplug_mutex);
-
-	/* for exclusive hibernation if CONFIG_HIBERNATION=y */
-	lock_system_sleep();
 }
 
 void unlock_memory_hotplug(void)
 {
-	unlock_system_sleep();
 	mutex_unlock(&mem_hotplug_mutex);
 }
 

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