X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=mm%2Fdmapool.c;h=fd5fe4342e9320de634db2e92d9757dd1677f5be;hb=27a9716bc80448f7e98fb1fb316daba241a4c539;hp=ba8019b063e18ecb14da4cf3a64dfa671586f8e0;hpb=1e345ac6869cd2f2d5d4b780fc5d5332dd1e8905;p=firefly-linux-kernel-4.4.55.git

diff --git a/mm/dmapool.c b/mm/dmapool.c
index ba8019b063e1..fd5fe4342e93 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -62,6 +62,7 @@ struct dma_page {		/* cacheable header for 'allocation' bytes */
 };
 
 static DEFINE_MUTEX(pools_lock);
+static DEFINE_MUTEX(pools_reg_lock);
 
 static ssize_t
 show_pools(struct device *dev, struct device_attribute *attr, char *buf)
@@ -132,29 +133,27 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
 {
 	struct dma_pool *retval;
 	size_t allocation;
+	bool empty = false;
 
-	if (align == 0) {
+	if (align == 0)
 		align = 1;
-	} else if (align & (align - 1)) {
+	else if (align & (align - 1))
 		return NULL;
-	}
 
-	if (size == 0) {
+	if (size == 0)
 		return NULL;
-	} else if (size < 4) {
+	else if (size < 4)
 		size = 4;
-	}
 
 	if ((size % align) != 0)
 		size = ALIGN(size, align);
 
 	allocation = max_t(size_t, size, PAGE_SIZE);
 
-	if (!boundary) {
+	if (!boundary)
 		boundary = allocation;
-	} else if ((boundary < size) || (boundary & (boundary - 1))) {
+	else if ((boundary < size) || (boundary & (boundary - 1)))
 		return NULL;
-	}
 
 	retval = kmalloc_node(sizeof(*retval), GFP_KERNEL, dev_to_node(dev));
 	if (!retval)
@@ -172,15 +171,34 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev,
 
 	INIT_LIST_HEAD(&retval->pools);
 
+	/*
+	 * pools_lock ensures that the ->dma_pools list does not get corrupted.
+	 * pools_reg_lock ensures that there is not a race between
+	 * dma_pool_create() and dma_pool_destroy() or within dma_pool_create()
+	 * when the first invocation of dma_pool_create() failed on
+	 * device_create_file() and the second assumes that it has been done (I
+	 * know it is a short window).
+	 */
+	mutex_lock(&pools_reg_lock);
 	mutex_lock(&pools_lock);
-	if (list_empty(&dev->dma_pools) &&
-	    device_create_file(dev, &dev_attr_pools)) {
-		kfree(retval);
-		retval = NULL;
-	} else
-		list_add(&retval->pools, &dev->dma_pools);
+	if (list_empty(&dev->dma_pools))
+		empty = true;
+	list_add(&retval->pools, &dev->dma_pools);
 	mutex_unlock(&pools_lock);
-
+	if (empty) {
+		int err;
+
+		err = device_create_file(dev, &dev_attr_pools);
+		if (err) {
+			mutex_lock(&pools_lock);
+			list_del(&retval->pools);
+			mutex_unlock(&pools_lock);
+			mutex_unlock(&pools_reg_lock);
+			kfree(retval);
+			return NULL;
+		}
+	}
+	mutex_unlock(&pools_reg_lock);
 	return retval;
 }
 EXPORT_SYMBOL(dma_pool_create);
@@ -251,11 +269,17 @@ static void pool_free_page(struct dma_pool *pool, struct dma_page *page)
  */
 void dma_pool_destroy(struct dma_pool *pool)
 {
+	bool empty = false;
+
+	mutex_lock(&pools_reg_lock);
 	mutex_lock(&pools_lock);
 	list_del(&pool->pools);
 	if (pool->dev && list_empty(&pool->dev->dma_pools))
-		device_remove_file(pool->dev, &dev_attr_pools);
+		empty = true;
 	mutex_unlock(&pools_lock);
+	if (empty)
+		device_remove_file(pool->dev, &dev_attr_pools);
+	mutex_unlock(&pools_reg_lock);
 
 	while (!list_empty(&pool->page_list)) {
 		struct dma_page *page;