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Subject[PATCH 042/115] gpu: ion: Refactor locking
Date
From: Rebecca Schultz Zavin <rebecca@android.com>

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>
---
drivers/staging/android/ion/ion.c | 45 ++++++++++++++++++++++-----------------
1 file changed, 25 insertions(+), 20 deletions(-)

diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index 0070c9b..ef8f132 100644
--- 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;
--
1.8.3.2


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