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Subject[19/20] dca: redesign locks to fix deadlocks
2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Maciej Sosnowski <maciej.sosnowski@intel.com>
commit eb4400e3a040b90a3ad805b01fcbc99a5f615c8f upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/dca/dca-core.c | 51 +++++++++++++++++++++++++++++++------------------
1 file changed, 33 insertions(+), 18 deletions(-)
--- 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 *
{
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
{
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_provid
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);



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