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Commit 6a72a700 authored by John Stultz's avatar John Stultz Committed by Greg Kroah-Hartman
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staging: ion: Avoid using rt_mutexes directly 



RT_MUTEXES can be configured out of the kernel, causing compile
problems with ION.

To quote Colin:
"rt_mutexes were added with the deferred freeing feature.  Heaps need
to return zeroed memory to userspace, but zeroing the memory on every
allocation was causing performance issues.  We added a SCHED_IDLE
thread to zero memory in the background after freeing, but locking the
heap from the SCHED_IDLE thread might block a high priority allocation
thread for a long time.

The lock is only used to protect the heap's free_list and
free_list_size members, and is not held for any long or sleeping
operations.  Converting to a spinlock should prevent priority
inversion without using the rt_mutex.  I'd also rename it to free_lock
to so it doesn't get used as a general heap lock."

Thus this patch converts the rt_mutex usage to a spinlock and
renames the lock free_lock to be more clear as to its use.

I also had to change a bit of logic in ion_heap_freelist_drain()
to safely avoid list corruption.

Acked-by: default avatarColin Cross <ccross@android.com>
Cc: Android Kernel Team <kernel-team@android.com>
Reported-by: default avatarJim Davis <jim.epost@gmail.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7dcfee65

drivers/staging/android/ion/ion_heap.c

+16 −12
Original line number Diff line number Diff line
@@ -160,10 +160,10 @@ int ion_heap_pages_zero(struct page *page, size_t size, pgprot_t pgprot) 


void ion_heap_freelist_add(struct ion_heap *heap, struct ion_buffer *buffer)

{

	rt_mutex_lock(&heap->lock);

	spin_lock(&heap->free_lock);

	list_add(&buffer->list, &heap->free_list);

	heap->free_list_size += buffer->size;

	rt_mutex_unlock(&heap->lock);

	spin_unlock(&heap->free_lock);

	wake_up(&heap->waitqueue);

}
@@ -171,34 +171,38 @@ size_t ion_heap_freelist_size(struct ion_heap *heap) 
{

	size_t size;



	rt_mutex_lock(&heap->lock);

	spin_lock(&heap->free_lock);

	size = heap->free_list_size;

	rt_mutex_unlock(&heap->lock);

	spin_unlock(&heap->free_lock);



	return size;

}



size_t ion_heap_freelist_drain(struct ion_heap *heap, size_t size)

{

	struct ion_buffer *buffer, *tmp;

	struct ion_buffer *buffer;

	size_t total_drained = 0;



	if (ion_heap_freelist_size(heap) == 0)

		return 0;



	rt_mutex_lock(&heap->lock);

	spin_lock(&heap->free_lock);

	if (size == 0)

		size = heap->free_list_size;



	list_for_each_entry_safe(buffer, tmp, &heap->free_list, list) {

	while (!list_empty(&heap->free_list)) {

		if (total_drained >= size)

			break;

		buffer = list_first_entry(&heap->free_list, struct ion_buffer,

					  list);

		list_del(&buffer->list);

		heap->free_list_size -= buffer->size;

		total_drained += buffer->size;

		spin_unlock(&heap->free_lock);

		ion_buffer_destroy(buffer);

		spin_lock(&heap->free_lock);

	}

	rt_mutex_unlock(&heap->lock);

	spin_unlock(&heap->free_lock);



	return total_drained;

}
@@ -213,16 +217,16 @@ static int ion_heap_deferred_free(void *data) 
		wait_event_freezable(heap->waitqueue,

				     ion_heap_freelist_size(heap) > 0);



		rt_mutex_lock(&heap->lock);

		spin_lock(&heap->free_lock);

		if (list_empty(&heap->free_list)) {

			rt_mutex_unlock(&heap->lock);

			spin_unlock(&heap->free_lock);

			continue;

		}

		buffer = list_first_entry(&heap->free_list, struct ion_buffer,

					  list);

		list_del(&buffer->list);

		heap->free_list_size -= buffer->size;

		rt_mutex_unlock(&heap->lock);

		spin_unlock(&heap->free_lock);

		ion_buffer_destroy(buffer);

	}
@@ -235,7 +239,7 @@ int ion_heap_init_deferred_free(struct ion_heap *heap) 


	INIT_LIST_HEAD(&heap->free_list);

	heap->free_list_size = 0;

	rt_mutex_init(&heap->lock);

	spin_lock_init(&heap->free_lock);

	init_waitqueue_head(&heap->waitqueue);

	heap->task = kthread_run(ion_heap_deferred_free, heap,

				 "%s", heap->name);

drivers/staging/android/ion/ion_priv.h

+1 −1
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ struct ion_heap { 
	struct shrinker shrinker;

	struct list_head free_list;

	size_t free_list_size;

	struct rt_mutex lock;

	spinlock_t free_lock;

	wait_queue_head_t waitqueue;

	struct task_struct *task;

	int (*debug_show)(struct ion_heap *heap, struct seq_file *, void *);