PM / Clocks: Do not acquire a mutex under a spinlock
Commit b7ab83e (PM: Use spinlock instead of mutex in clock
management functions) introduced a regression causing clocks_mutex
to be acquired under a spinlock. This happens because
pm_clk_suspend() and pm_clk_resume() call pm_clk_acquire() under
pcd->lock, but pm_clk_acquire() executes clk_get() which causes
clocks_mutex to be acquired. Similarly, __pm_clk_remove(),
executed under pcd->lock, calls clk_put(), which also causes
clocks_mutex to be acquired.
To fix those problems make pm_clk_add() call pm_clk_acquire(), so
that pm_clk_suspend() and pm_clk_resume() don't have to do that.
Change pm_clk_remove() and pm_clk_destroy() to separate
modifications of the pcd->clock_list list from the actual removal of
PM clock entry objects done by __pm_clk_remove().
Reported-and-tested-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index 2c18d58..b97294e 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -42,6 +42,22 @@
}
/**
+ * pm_clk_acquire - Acquire a device clock.
+ * @dev: Device whose clock is to be acquired.
+ * @ce: PM clock entry corresponding to the clock.
+ */
+static void pm_clk_acquire(struct device *dev, struct pm_clock_entry *ce)
+{
+ ce->clk = clk_get(dev, ce->con_id);
+ if (IS_ERR(ce->clk)) {
+ ce->status = PCE_STATUS_ERROR;
+ } else {
+ ce->status = PCE_STATUS_ACQUIRED;
+ dev_dbg(dev, "Clock %s managed by runtime PM.\n", ce->con_id);
+ }
+}
+
+/**
* pm_clk_add - Start using a device clock for power management.
* @dev: Device whose clock is going to be used for power management.
* @con_id: Connection ID of the clock.
@@ -73,6 +89,8 @@
}
}
+ pm_clk_acquire(dev, ce);
+
spin_lock_irq(&pcd->lock);
list_add_tail(&ce->node, &pcd->clock_list);
spin_unlock_irq(&pcd->lock);
@@ -82,17 +100,12 @@
/**
* __pm_clk_remove - Destroy PM clock entry.
* @ce: PM clock entry to destroy.
- *
- * This routine must be called under the spinlock protecting the PM list of
- * clocks corresponding the the @ce's device.
*/
static void __pm_clk_remove(struct pm_clock_entry *ce)
{
if (!ce)
return;
- list_del(&ce->node);
-
if (ce->status < PCE_STATUS_ERROR) {
if (ce->status == PCE_STATUS_ENABLED)
clk_disable(ce->clk);
@@ -126,18 +139,22 @@
spin_lock_irq(&pcd->lock);
list_for_each_entry(ce, &pcd->clock_list, node) {
- if (!con_id && !ce->con_id) {
- __pm_clk_remove(ce);
- break;
- } else if (!con_id || !ce->con_id) {
+ if (!con_id && !ce->con_id)
+ goto remove;
+ else if (!con_id || !ce->con_id)
continue;
- } else if (!strcmp(con_id, ce->con_id)) {
- __pm_clk_remove(ce);
- break;
- }
+ else if (!strcmp(con_id, ce->con_id))
+ goto remove;
}
spin_unlock_irq(&pcd->lock);
+ return;
+
+ remove:
+ list_del(&ce->node);
+ spin_unlock_irq(&pcd->lock);
+
+ __pm_clk_remove(ce);
}
/**
@@ -175,20 +192,27 @@
{
struct pm_clk_data *pcd = __to_pcd(dev);
struct pm_clock_entry *ce, *c;
+ struct list_head list;
if (!pcd)
return;
dev->power.subsys_data = NULL;
+ INIT_LIST_HEAD(&list);
spin_lock_irq(&pcd->lock);
list_for_each_entry_safe_reverse(ce, c, &pcd->clock_list, node)
- __pm_clk_remove(ce);
+ list_move(&ce->node, &list);
spin_unlock_irq(&pcd->lock);
kfree(pcd);
+
+ list_for_each_entry_safe_reverse(ce, c, &list, node) {
+ list_del(&ce->node);
+ __pm_clk_remove(ce);
+ }
}
#endif /* CONFIG_PM */
@@ -196,23 +220,6 @@
#ifdef CONFIG_PM_RUNTIME
/**
- * pm_clk_acquire - Acquire a device clock.
- * @dev: Device whose clock is to be acquired.
- * @con_id: Connection ID of the clock.
- */
-static void pm_clk_acquire(struct device *dev,
- struct pm_clock_entry *ce)
-{
- ce->clk = clk_get(dev, ce->con_id);
- if (IS_ERR(ce->clk)) {
- ce->status = PCE_STATUS_ERROR;
- } else {
- ce->status = PCE_STATUS_ACQUIRED;
- dev_dbg(dev, "Clock %s managed by runtime PM.\n", ce->con_id);
- }
-}
-
-/**
* pm_clk_suspend - Disable clocks in a device's PM clock list.
* @dev: Device to disable the clocks for.
*/
@@ -230,9 +237,6 @@
spin_lock_irqsave(&pcd->lock, flags);
list_for_each_entry_reverse(ce, &pcd->clock_list, node) {
- if (ce->status == PCE_STATUS_NONE)
- pm_clk_acquire(dev, ce);
-
if (ce->status < PCE_STATUS_ERROR) {
clk_disable(ce->clk);
ce->status = PCE_STATUS_ACQUIRED;
@@ -262,9 +266,6 @@
spin_lock_irqsave(&pcd->lock, flags);
list_for_each_entry(ce, &pcd->clock_list, node) {
- if (ce->status == PCE_STATUS_NONE)
- pm_clk_acquire(dev, ce);
-
if (ce->status < PCE_STATUS_ERROR) {
clk_enable(ce->clk);
ce->status = PCE_STATUS_ENABLED;