3.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
commit 22e71691fd54c637800d10816bbeba9cf132d218 upstream.
I can observe that RHEL7 environment stalls with 100% CPU usage when a
certain type of memory pressure is given. While the shrinker functions
are called by shrink_slab() before the OOM killer is triggered, the stall
lasts for many minutes.
One of reasons of this stall is that
ttm_dma_pool_shrink_count()/ttm_dma_pool_shrink_scan() are called and
are blocked at mutex_lock(&_manager->lock). GFP_KERNEL allocation with
_manager->lock held causes someone (including kswapd) to deadlock when
these functions are called due to memory pressure. This patch changes
"mutex_lock();" to "if (!mutex_trylock()) return ...;" in order to
avoid deadlock.
Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
Signed-off-by: Dave Airlie <airl...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -1014,7 +1014,8 @@ ttm_dma_pool_shrink_scan(struct shrinker
if (list_empty(&_manager->pools))
return SHRINK_STOP;
- mutex_lock(&_manager->lock);
+ if (!mutex_trylock(&_manager->lock))
+ return SHRINK_STOP;
if (!_manager->npools)
goto out;
pool_offset = ++start_pool % _manager->npools;
@@ -1047,7 +1048,8 @@ ttm_dma_pool_shrink_count(struct shrinke
struct device_pools *p;
unsigned long count = 0;
- mutex_lock(&_manager->lock);
+ if (!mutex_trylock(&_manager->lock))
+ return 0;
list_for_each_entry(p, &_manager->pools, pools)
count += p->pool->npages_free;
mutex_unlock(&_manager->lock);
--
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