gpu: ion: Refactor locking

Removes contention for lock between allocate and free by reducing
the length of time the lock is held for.  Split out a seperate
lock to protect the list of heaps and replace it with a rwsem since
the list will most likely only be updated during initialization.

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
[jstultz: modified patch to apply to staging directory]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 0070c9b..ef8f132 100644 (file)
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -38,15 +38,17 @@
 /**
  * struct ion_device - the metadata of the ion device node
  * @dev:               the actual misc device
- * @buffers:   an rb tree of all the existing buffers
- * @lock:              lock protecting the buffers & heaps trees
+ * @buffers:           an rb tree of all the existing buffers
+ * @buffer_lock:       lock protecting the tree of buffers
+ * @lock:              rwsem protecting the tree of heaps and clients
  * @heaps:             list of all the heaps in the system
  * @user_clients:      list of all the clients created from userspace
  */
 struct ion_device {
        struct miscdevice dev;
        struct rb_root buffers;
-       struct mutex lock;
+       struct mutex buffer_lock;
+       struct rw_semaphore lock;
        struct rb_root heaps;
        long (*custom_ioctl) (struct ion_client *client, unsigned int cmd,
                              unsigned long arg);
@@ -205,7 +207,9 @@ static struct ion_buffer *ion_buffer_create(struct ion_heap *heap,
           cached mapping that mapping has been invalidated */
        for_each_sg(buffer->sg_table->sgl, sg, buffer->sg_table->nents, i)
                sg_dma_address(sg) = sg_phys(sg);
+       mutex_lock(&dev->buffer_lock);
        ion_buffer_add(dev, buffer);
+       mutex_unlock(&dev->buffer_lock);
        return buffer;
 
 err:
@@ -224,9 +228,9 @@ static void ion_buffer_destroy(struct kref *kref)
                buffer->heap->ops->unmap_kernel(buffer->heap, buffer);
        buffer->heap->ops->unmap_dma(buffer->heap, buffer);
        buffer->heap->ops->free(buffer);
-       mutex_lock(&dev->lock);
+       mutex_lock(&dev->buffer_lock);
        rb_erase(&buffer->node, &dev->buffers);
-       mutex_unlock(&dev->lock);
+       mutex_unlock(&dev->buffer_lock);
        if (buffer->flags & ION_FLAG_CACHED)
                kfree(buffer->dirty);
        kfree(buffer);
@@ -244,9 +248,9 @@ static int ion_buffer_put(struct ion_buffer *buffer)
 
 static void ion_buffer_add_to_handle(struct ion_buffer *buffer)
 {
-       mutex_lock(&buffer->dev->lock);
+       mutex_lock(&buffer->lock);
        buffer->handle_count++;
-       mutex_unlock(&buffer->dev->lock);
+       mutex_unlock(&buffer->lock);
 }
 
 static void ion_buffer_remove_from_handle(struct ion_buffer *buffer)
@@ -260,7 +264,7 @@ static void ion_buffer_remove_from_handle(struct ion_buffer *buffer)
         * The taskcomm and pid can provide a debug hint as to where this fd
         * is in the system
         */
-       mutex_lock(&buffer->dev->lock);
+       mutex_lock(&buffer->lock);
        buffer->handle_count--;
        BUG_ON(buffer->handle_count < 0);
        if (!buffer->handle_count) {
@@ -270,7 +274,7 @@ static void ion_buffer_remove_from_handle(struct ion_buffer *buffer)
                get_task_comm(buffer->task_comm, task);
                buffer->pid = task_pid_nr(task);
        }
-       mutex_unlock(&buffer->dev->lock);
+       mutex_unlock(&buffer->lock);
 }
 
 static struct ion_handle *ion_handle_create(struct ion_client *client,
@@ -403,7 +407,7 @@ struct ion_handle *ion_alloc(struct ion_client *client, size_t len,
 
        len = PAGE_ALIGN(len);
 
-       mutex_lock(&dev->lock);
+       down_read(&dev->lock);
        for (n = rb_first(&dev->heaps); n != NULL; n = rb_next(n)) {
                struct ion_heap *heap = rb_entry(n, struct ion_heap, node);
                /* if the client doesn't support this heap type */
@@ -416,7 +420,7 @@ struct ion_handle *ion_alloc(struct ion_client *client, size_t len,
                if (!IS_ERR_OR_NULL(buffer))
                        break;
        }
-       mutex_unlock(&dev->lock);
+       up_read(&dev->lock);
 
        if (buffer == NULL)
                return ERR_PTR(-ENODEV);
@@ -662,7 +666,7 @@ struct ion_client *ion_client_create(struct ion_device *dev,
        client->task = task;
        client->pid = pid;
 
-       mutex_lock(&dev->lock);
+       down_write(&dev->lock);
        p = &dev->clients.rb_node;
        while (*p) {
                parent = *p;
@@ -680,7 +684,7 @@ struct ion_client *ion_client_create(struct ion_device *dev,
        client->debug_root = debugfs_create_file(debug_name, 0664,
                                                 dev->debug_root, client,
                                                 &debug_client_fops);
-       mutex_unlock(&dev->lock);
+       up_write(&dev->lock);
 
        return client;
 }
@@ -696,12 +700,12 @@ void ion_client_destroy(struct ion_client *client)
                                                     node);
                ion_handle_destroy(&handle->ref);
        }
-       mutex_lock(&dev->lock);
+       down_write(&dev->lock);
        if (client->task)
                put_task_struct(client->task);
        rb_erase(&client->node, &dev->clients);
        debugfs_remove_recursive(client->debug_root);
-       mutex_unlock(&dev->lock);
+       up_write(&dev->lock);
 
        kfree(client);
 }
@@ -1220,7 +1224,7 @@ static int ion_debug_heap_show(struct seq_file *s, void *unused)
        seq_printf(s, "----------------------------------------------------\n");
        seq_printf(s, "orphaned allocations (info is from last known client):"
                   "\n");
-       mutex_lock(&dev->lock);
+       mutex_lock(&dev->buffer_lock);
        for (n = rb_first(&dev->buffers); n; n = rb_next(n)) {
                struct ion_buffer *buffer = rb_entry(n, struct ion_buffer,
                                                     node);
@@ -1233,7 +1237,7 @@ static int ion_debug_heap_show(struct seq_file *s, void *unused)
                        total_orphaned_size += buffer->size;
                }
        }
-       mutex_unlock(&dev->lock);
+       mutex_unlock(&dev->buffer_lock);
        seq_printf(s, "----------------------------------------------------\n");
        seq_printf(s, "%16.s %16u\n", "total orphaned",
                   total_orphaned_size);
@@ -1270,7 +1274,7 @@ void ion_device_add_heap(struct ion_device *dev, struct ion_heap *heap)
                       __func__);
 
        heap->dev = dev;
-       mutex_lock(&dev->lock);
+       down_write(&dev->lock);
        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct ion_heap, node);
@@ -1291,7 +1295,7 @@ void ion_device_add_heap(struct ion_device *dev, struct ion_heap *heap)
        debugfs_create_file(heap->name, 0664, dev->debug_root, heap,
                            &debug_heap_fops);
 end:
-       mutex_unlock(&dev->lock);
+       up_write(&dev->lock);
 }
 
 struct ion_device *ion_device_create(long (*custom_ioctl)
@@ -1322,7 +1326,8 @@ struct ion_device *ion_device_create(long (*custom_ioctl)
 
        idev->custom_ioctl = custom_ioctl;
        idev->buffers = RB_ROOT;
-       mutex_init(&idev->lock);
+       mutex_init(&idev->buffer_lock);
+       init_rwsem(&idev->lock);
        idev->heaps = RB_ROOT;
        idev->clients = RB_ROOT;
        return idev;