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Subject[PATCH 4/8] PM: Do not acquire device semaphores upfront during suspend
Date
From: Rafael J. Wysocki <rjw@sisk.pl>

Remove the code that acquires all device semaphores from the suspend
code path as it causes multiple problems to appear (most notably,
http://bugzilla.kernel.org/show_bug.cgi?id=10030) and revert the
change introduced by commit 4145ed6dc597a9bea5f6ae8c574653b2de10620f
depending on the code being removed.

Remove pm_sleep_lock()/pm_sleep_unlock() from device_add() to avoid
the issue reported at http://bugzilla.kernel.org/show_bug.cgi?id=9874.

It should fix the regreesions reported at:
http://bugzilla.kernel.org/show_bug.cgi?id=9874
http://bugzilla.kernel.org/show_bug.cgi?id=10030

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/base/core.c | 8 ---
drivers/base/power/main.c | 106 +++++++--------------------------------------
drivers/usb/core/usb.c | 2 +-
3 files changed, 17 insertions(+), 99 deletions(-)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 9c0070b..1e2e0fa 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -770,13 +770,6 @@ int device_add(struct device *dev)
struct class_interface *class_intf;
int error;

- error = pm_sleep_lock();
- if (error) {
- dev_warn(dev, "Suspicious %s during suspend\n", __FUNCTION__);
- dump_stack();
- return error;
- }
-
dev = get_device(dev);
if (!dev || !strlen(dev->bus_id)) {
error = -EINVAL;
@@ -843,7 +836,6 @@ int device_add(struct device *dev)
}
Done:
put_device(dev);
- pm_sleep_unlock();
return error;
BusError:
device_pm_remove(dev);
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index ee9d1c8..b0c16f6 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -48,7 +48,6 @@
*/

LIST_HEAD(dpm_active);
-static LIST_HEAD(dpm_locked);
static LIST_HEAD(dpm_off);
static LIST_HEAD(dpm_off_irq);
static LIST_HEAD(dpm_destroy);
@@ -81,28 +80,6 @@ void device_pm_add(struct device *dev)
*/
void device_pm_remove(struct device *dev)
{
- /*
- * If this function is called during a suspend, it will be blocked,
- * because we're holding the device's semaphore at that time, which may
- * lead to a deadlock. In that case we want to print a warning.
- * However, it may also be called by unregister_dropped_devices() with
- * the device's semaphore released, in which case the warning should
- * not be printed.
- */
- if (down_trylock(&dev->sem)) {
- if (down_read_trylock(&pm_sleep_rwsem)) {
- /* No suspend in progress, wait on dev->sem */
- down(&dev->sem);
- up_read(&pm_sleep_rwsem);
- } else {
- /* Suspend in progress, we may deadlock */
- dev_warn(dev, "Suspicious %s during suspend\n",
- __FUNCTION__);
- dump_stack();
- /* The user has been warned ... */
- down(&dev->sem);
- }
- }
pr_debug("PM: Removing info for %s:%s\n",
dev->bus ? dev->bus->name : "No Bus",
kobject_name(&dev->kobj));
@@ -110,7 +87,6 @@ void device_pm_remove(struct device *dev)
dpm_sysfs_remove(dev);
list_del_init(&dev->power.entry);
mutex_unlock(&dpm_list_mtx);
- up(&dev->sem);
}

/**
@@ -230,6 +206,8 @@ static int resume_device(struct device *dev)
TRACE_DEVICE(dev);
TRACE_RESUME(0);

+ down(&dev->sem);
+
if (dev->bus && dev->bus->resume) {
dev_dbg(dev,"resuming\n");
error = dev->bus->resume(dev);
@@ -245,6 +223,8 @@ static int resume_device(struct device *dev)
error = dev->class->resume(dev);
}

+ up(&dev->sem);
+
TRACE_RESUME(error);
return error;
}
@@ -266,7 +246,7 @@ static void dpm_resume(void)
struct list_head *entry = dpm_off.next;
struct device *dev = to_device(entry);

- list_move_tail(entry, &dpm_locked);
+ list_move_tail(entry, &dpm_active);
mutex_unlock(&dpm_list_mtx);
resume_device(dev);
mutex_lock(&dpm_list_mtx);
@@ -275,25 +255,6 @@ static void dpm_resume(void)
}

/**
- * unlock_all_devices - Release each device's semaphore
- *
- * Go through the dpm_off list. Put each device on the dpm_active
- * list and unlock it.
- */
-static void unlock_all_devices(void)
-{
- mutex_lock(&dpm_list_mtx);
- while (!list_empty(&dpm_locked)) {
- struct list_head *entry = dpm_locked.prev;
- struct device *dev = to_device(entry);
-
- list_move(entry, &dpm_active);
- up(&dev->sem);
- }
- mutex_unlock(&dpm_list_mtx);
-}
-
-/**
* unregister_dropped_devices - Unregister devices scheduled for removal
*
* Unregister all devices on the dpm_destroy list.
@@ -305,7 +266,6 @@ static void unregister_dropped_devices(void)
struct list_head *entry = dpm_destroy.next;
struct device *dev = to_device(entry);

- up(&dev->sem);
mutex_unlock(&dpm_list_mtx);
/* This also removes the device from the list */
device_unregister(dev);
@@ -324,7 +284,6 @@ void device_resume(void)
{
might_sleep();
dpm_resume();
- unlock_all_devices();
unregister_dropped_devices();
up_write(&pm_sleep_rwsem);
}
@@ -388,18 +347,15 @@ int device_power_down(pm_message_t state)
struct list_head *entry = dpm_off.prev;
struct device *dev = to_device(entry);

- list_del_init(&dev->power.entry);
error = suspend_device_late(dev, state);
if (error) {
printk(KERN_ERR "Could not power down device %s: "
"error %d\n",
kobject_name(&dev->kobj), error);
- if (list_empty(&dev->power.entry))
- list_add(&dev->power.entry, &dpm_off);
break;
}
- if (list_empty(&dev->power.entry))
- list_add(&dev->power.entry, &dpm_off_irq);
+ if (!list_empty(&dev->power.entry))
+ list_move(&dev->power.entry, &dpm_off_irq);
}

if (!error)
@@ -419,6 +375,8 @@ static int suspend_device(struct device *dev, pm_message_t state)
{
int error = 0;

+ down(&dev->sem);
+
if (dev->power.power_state.event) {
dev_dbg(dev, "PM: suspend %d-->%d\n",
dev->power.power_state.event, state.event);
@@ -441,6 +399,9 @@ static int suspend_device(struct device *dev, pm_message_t state)
error = dev->bus->suspend(dev, state);
suspend_report_result(dev->bus->suspend, error);
}
+
+ up(&dev->sem);
+
return error;
}

@@ -461,11 +422,10 @@ static int dpm_suspend(pm_message_t state)
int error = 0;

mutex_lock(&dpm_list_mtx);
- while (!list_empty(&dpm_locked)) {
- struct list_head *entry = dpm_locked.prev;
+ while (!list_empty(&dpm_active)) {
+ struct list_head *entry = dpm_active.prev;
struct device *dev = to_device(entry);

- list_del_init(&dev->power.entry);
mutex_unlock(&dpm_list_mtx);
error = suspend_device(dev, state);
if (error) {
@@ -476,14 +436,11 @@ static int dpm_suspend(pm_message_t state)
(error == -EAGAIN ?
" (please convert to suspend_late)" :
""));
- mutex_lock(&dpm_list_mtx);
- if (list_empty(&dev->power.entry))
- list_add(&dev->power.entry, &dpm_locked);
break;
}
mutex_lock(&dpm_list_mtx);
- if (list_empty(&dev->power.entry))
- list_add(&dev->power.entry, &dpm_off);
+ if (!list_empty(&dev->power.entry))
+ list_move(&dev->power.entry, &dpm_off);
}
mutex_unlock(&dpm_list_mtx);

@@ -491,36 +448,6 @@ static int dpm_suspend(pm_message_t state)
}

/**
- * lock_all_devices - Acquire every device's semaphore
- *
- * Go through the dpm_active list. Carefully lock each device's
- * semaphore and put it in on the dpm_locked list.
- */
-static void lock_all_devices(void)
-{
- mutex_lock(&dpm_list_mtx);
- while (!list_empty(&dpm_active)) {
- struct list_head *entry = dpm_active.next;
- struct device *dev = to_device(entry);
-
- /* Required locking order is dev->sem first,
- * then dpm_list_mutex. Hence this awkward code.
- */
- get_device(dev);
- mutex_unlock(&dpm_list_mtx);
- down(&dev->sem);
- mutex_lock(&dpm_list_mtx);
-
- if (list_empty(entry))
- up(&dev->sem); /* Device was removed */
- else
- list_move_tail(entry, &dpm_locked);
- put_device(dev);
- }
- mutex_unlock(&dpm_list_mtx);
-}
-
-/**
* device_suspend - Save state and stop all devices in system.
* @state: new power management state
*
@@ -533,7 +460,6 @@ int device_suspend(pm_message_t state)

might_sleep();
down_write(&pm_sleep_rwsem);
- lock_all_devices();
error = dpm_suspend(state);
if (error)
device_resume();
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index f6f1990..1f0db51 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -233,7 +233,7 @@ static int ksuspend_usb_init(void)
* singlethreaded. Its job doesn't justify running on more
* than one CPU.
*/
- ksuspend_usb_wq = create_singlethread_workqueue("ksuspend_usbd");
+ ksuspend_usb_wq = create_freezeable_workqueue("ksuspend_usbd");
if (!ksuspend_usb_wq)
return -ENOMEM;
return 0;
--
1.5.4.3


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