From 6a72a700f44b2fa1b1d6f3529e5d492a4f71de49 Mon Sep 17 00:00:00 2001 From: John Stultz Date: Tue, 17 Dec 2013 17:04:29 -0800 Subject: [PATCH] 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: Colin Cross Cc: Android Kernel Team Reported-by: Jim Davis Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/ion/ion_heap.c | 28 ++++++++++++++++------------ drivers/staging/android/ion/ion_priv.h | 2 +- 2 files changed, 17 insertions(+), 13 deletions(-) diff --git a/drivers/staging/android/ion/ion_heap.c b/drivers/staging/android/ion/ion_heap.c index 9cf5622..296c74f 100644 --- a/drivers/staging/android/ion/ion_heap.c +++ b/drivers/staging/android/ion/ion_heap.c @@ -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); diff --git a/drivers/staging/android/ion/ion_priv.h b/drivers/staging/android/ion/ion_priv.h index fc8a4c3..d986739 100644 --- a/drivers/staging/android/ion/ion_priv.h +++ b/drivers/staging/android/ion/ion_priv.h @@ -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 *); -- 2.7.4