[PATCH] mm/dmapool.c: Do not create/destroy sysfs file while holding pools_lock
STALE5693d
From: Russ Meyerriecks <hidden>
Date: 2011-02-28 23:03:05
Also in:
lkml
Subsystem:
memory management, memory management - misc, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
From: Shaun Ruffell <redacted>
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: [<c04ef113>] show_pools+0x43/0x140
but task is already holding lock:
(s_active#82){++++.+}, at: [<c0554e1b>] sysfs_read_file+0xab/0x160
which lock already depends on the new lock.
Signed-off-by: Shaun Ruffell <redacted>
Signed-off-by: Russ Meyerriecks <redacted>
---
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
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