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>

diff --git a/drivers/dca/dca-core.c b/drivers/dca/dca-core.c
index 55433849bfa67a30a1cbddd5724f076057f476a4..33bd7534751820841d19732a5d5e79b4dea9adbf 100644 (file)
--- 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);