dca: redesign locks to fix deadlocks

Change spin_locks to irqsave to prevent dead-locks.
Protect adding and deleting to/from dca_providers list.
Drop the lock during dca_sysfs_add_req() and dca_sysfs_remove_req() calls
as they might sleep (use GFP_KERNEL allocation).

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 33 insertions, 18 deletions

diff --git a/drivers/dca/dca-core.c b/drivers/dca/dca-core.c
index 55433849bfa6..33bd75347518 100644
--- a/drivers/dca/dca-core.c
+++ b/drivers/dca/dca-core.c
@@ -28,7 +28,7 @@
 #include <linux/device.h>
 #include <linux/dca.h>
 
-#define DCA_VERSION "1.4"
+#define DCA_VERSION "1.8"
 
 MODULE_VERSION(DCA_VERSION);
 MODULE_LICENSE("GPL");
@@ -60,16 +60,17 @@ int dca_add_requester(struct device *dev)
 {
         struct dca_provider *dca;
         int err, slot = -ENODEV;
+        unsigned long flags;
 
         if (!dev)
                 return -EFAULT;
 
-        spin_lock(&dca_lock);
+        spin_lock_irqsave(&dca_lock, flags);
 
         /* check if the requester has not been added already */
         dca = dca_find_provider_by_dev(dev);
         if (dca) {
-                spin_unlock(&dca_lock);
+                spin_unlock_irqrestore(&dca_lock, flags);
                 return -EEXIST;
         }
 
@@ -78,19 +79,21 @@ int dca_add_requester(struct device *dev)
                 if (slot >= 0)
                         break;
         }
-        if (slot < 0) {
-                spin_unlock(&dca_lock);
+
+        spin_unlock_irqrestore(&dca_lock, flags);
+
+        if (slot < 0)
                 return slot;
-        }
 
         err = dca_sysfs_add_req(dca, dev, slot);
         if (err) {
-                dca->ops->remove_requester(dca, dev);
-                spin_unlock(&dca_lock);
+                spin_lock_irqsave(&dca_lock, flags);
+                if (dca == dca_find_provider_by_dev(dev))
+                        dca->ops->remove_requester(dca, dev);
+                spin_unlock_irqrestore(&dca_lock, flags);
                 return err;
         }
 
-        spin_unlock(&dca_lock);
         return 0;
 }
 EXPORT_SYMBOL_GPL(dca_add_requester);
@@ -103,25 +106,25 @@ int dca_remove_requester(struct device *dev)
 {
         struct dca_provider *dca;
         int slot;
+        unsigned long flags;
 
         if (!dev)
                 return -EFAULT;
 
-        spin_lock(&dca_lock);
+        spin_lock_irqsave(&dca_lock, flags);
         dca = dca_find_provider_by_dev(dev);
         if (!dca) {
-                spin_unlock(&dca_lock);
+                spin_unlock_irqrestore(&dca_lock, flags);
                 return -ENODEV;
         }
         slot = dca->ops->remove_requester(dca, dev);
-        if (slot < 0) {
-                spin_unlock(&dca_lock);
+        spin_unlock_irqrestore(&dca_lock, flags);
+
+        if (slot < 0)
                 return slot;
-        }
 
         dca_sysfs_remove_req(dca, slot);
 
-        spin_unlock(&dca_lock);
         return 0;
 }
 EXPORT_SYMBOL_GPL(dca_remove_requester);
@@ -135,17 +138,18 @@ u8 dca_common_get_tag(struct device *dev, int cpu)
 {
         struct dca_provider *dca;
         u8 tag;
+        unsigned long flags;
 
-        spin_lock(&dca_lock);
+        spin_lock_irqsave(&dca_lock, flags);
 
         dca = dca_find_provider_by_dev(dev);
         if (!dca) {
-                spin_unlock(&dca_lock);
+                spin_unlock_irqrestore(&dca_lock, flags);
                 return -ENODEV;
         }
         tag = dca->ops->get_tag(dca, dev, cpu);
 
-        spin_unlock(&dca_lock);
+        spin_unlock_irqrestore(&dca_lock, flags);
         return tag;
 }
 
@@ -217,11 +221,16 @@ static BLOCKING_NOTIFIER_HEAD(dca_provider_chain);
 int register_dca_provider(struct dca_provider *dca, struct device *dev)
 {
         int err;
+        unsigned long flags;
 
         err = dca_sysfs_add_provider(dca, dev);
         if (err)
                 return err;
+
+        spin_lock_irqsave(&dca_lock, flags);
         list_add(&dca->node, &dca_providers);
+        spin_unlock_irqrestore(&dca_lock, flags);
+
         blocking_notifier_call_chain(&dca_provider_chain,
                                      DCA_PROVIDER_ADD, NULL);
         return 0;
@@ -234,9 +243,15 @@ EXPORT_SYMBOL_GPL(register_dca_provider);
  */
 void unregister_dca_provider(struct dca_provider *dca)
 {
+        unsigned long flags;
+
         blocking_notifier_call_chain(&dca_provider_chain,
                                      DCA_PROVIDER_REMOVE, NULL);
+
+        spin_lock_irqsave(&dca_lock, flags);
         list_del(&dca->node);
+        spin_unlock_irqrestore(&dca_lock, flags);
+
         dca_sysfs_remove_provider(dca);
 }
 EXPORT_SYMBOL_GPL(unregister_dca_provider);