From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 5AAAE8D0039 for ; Mon, 28 Feb 2011 17:40:30 -0500 (EST) Date: Mon, 28 Feb 2011 16:41:24 -0600 From: Russ Meyerriecks Subject: [PATCH] mm/dmapool.c: Do not create/destroy sysfs file while holding pools_lock Message-ID: <20110228224124.GA31769@blackmagic.digium.internal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org Cc: sruffell@digium.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org From: Shaun Ruffell Eliminates a circular lock dependency reported by lockdep. When reading the "pools" file from a PCI device via sysfs, the s_active lock is acquired before the pools_lock. When unloading the driver and destroying the pool, pools_lock is acquired before the s_active lock. cat/12016 is trying to acquire lock: (pools_lock){+.+.+.}, at: [] show_pools+0x43/0x140 but task is already holding lock: (s_active#82){++++.+}, at: [] sysfs_read_file+0xab/0x160 which lock already depends on the new lock. Signed-off-by: Shaun Ruffell Signed-off-by: Russ Meyerriecks --- mm/dmapool.c | 34 ++++++++++++++++++++++++---------- 1 files changed, 24 insertions(+), 10 deletions(-) diff --git a/mm/dmapool.c b/mm/dmapool.c index 03bf3bb..d693872 100644 --- a/mm/dmapool.c +++ b/mm/dmapool.c @@ -174,21 +174,28 @@ struct dma_pool *dma_pool_create(const char *name, struct device *dev, init_waitqueue_head(&retval->waitq); if (dev) { - int ret; + int first_pool; mutex_lock(&pools_lock); if (list_empty(&dev->dma_pools)) - ret = device_create_file(dev, &dev_attr_pools); + first_pool = 1; else - ret = 0; + first_pool = 0; /* note: not currently insisting "name" be unique */ - if (!ret) - list_add(&retval->pools, &dev->dma_pools); - else { - kfree(retval); - retval = NULL; - } + list_add(&retval->pools, &dev->dma_pools); mutex_unlock(&pools_lock); + + if (first_pool) { + int ret; + ret = device_create_file(dev, &dev_attr_pools); + if (ret) { + mutex_lock(&pools_lock); + list_del(&retval->pools); + mutex_unlock(&pools_lock); + kfree(retval); + retval = NULL; + } + } } else INIT_LIST_HEAD(&retval->pools); @@ -263,12 +270,19 @@ static void pool_free_page(struct dma_pool *pool, struct dma_page *page) */ void dma_pool_destroy(struct dma_pool *pool) { + int last_pool; + 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); + last_pool = 1; + else + last_pool = 0; mutex_unlock(&pools_lock); + if (last_pool) + device_remove_file(pool->dev, &dev_attr_pools); + while (!list_empty(&pool->page_list)) { struct dma_page *page; page = list_entry(pool->page_list.next, -- 1.7.2.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org