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drm/ttm: Use mutex_trylock() to avoid deadlock inside shrinker functions. 

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-kernel@I-love.SAKURA.ne.jp>
Cc: stable <stable@kernel.org> [3.3+]
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Tetsuo Handa 2014-08-03 20:01:10 +09:00 committed by Dave Airlie
parent 46c2df68f0
commit 22e71691fd
1 changed files with 4 additions and 2 deletions
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6
drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
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@ -1014,7 +1014,8 @@ ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
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 shrinker *shrink, struct shrink_control *sc)
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);