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locking/mutex, drm: Introduce mutex_trylock_recursive()

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By popular DRM demand, introduce mutex_trylock_recursive() to fix up the
two GEM users.

Without this it is very easy for these drivers to get stuck in
low-memory situations and trigger OOM. Work is in progress to remove the
need for this in at least i915.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ding Tianhong <dingtianhong@huawei.com>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jason Low <jason.low2@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Terry Rudd <terry.rudd@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <Will.Deacon@arm.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra
2016-10-07 17:43:51 +02:00
committed by Ingo Molnar
parent 83f06168ef
commit 0f5225b024
4 changed files with 61 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
include/linux/mutex.h
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@@ -189,4 +189,35 @@ extern void mutex_unlock(struct mutex *lock);
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
/*
* These values are chosen such that FAIL and SUCCESS match the
* values of the regular mutex_trylock().
*/
enum mutex_trylock_recursive_enum {
MUTEX_TRYLOCK_FAILED = 0,
MUTEX_TRYLOCK_SUCCESS = 1,
MUTEX_TRYLOCK_RECURSIVE,
};
/**
* mutex_trylock_recursive - trylock variant that allows recursive locking
* @lock: mutex to be locked
*
* This function should not be used, _ever_. It is purely for hysterical GEM
* raisins, and once those are gone this will be removed.
*
* Returns:
* MUTEX_TRYLOCK_FAILED - trylock failed,
* MUTEX_TRYLOCK_SUCCESS - lock acquired,
* MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
*/
static inline __deprecated __must_check enum mutex_trylock_recursive_enum
mutex_trylock_recursive(struct mutex *lock)
{
if (unlikely(__mutex_owner(lock) == current))
return MUTEX_TRYLOCK_RECURSIVE;
return mutex_trylock(lock);
}
#endif /* __LINUX_MUTEX_H */