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>

1 files changed, 38 insertions, 37 deletions

diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index 2c18d584066d..b97294e2d95b 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -42,6 +42,22 @@ static struct pm_clk_data *__to_pcd(struct device *dev)
 }
 
 /**
+ * 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 @@ int pm_clk_add(struct device *dev, const char *con_id)
                 }
         }
 
+        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 @@ int pm_clk_add(struct device *dev, const char *con_id)
 /**
  * __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 @@ void pm_clk_remove(struct device *dev, const char *con_id)
         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 @@ void pm_clk_destroy(struct device *dev)
 {
         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 @@ void pm_clk_destroy(struct device *dev)
 #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 @@ int pm_clk_suspend(struct device *dev)
         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 @@ int pm_clk_resume(struct device *dev)
         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;