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authorPeter Zijlstra <peterz@infradead.org>2016-10-07 18:43:51 +0300
committerIngo Molnar <mingo@kernel.org>2016-11-15 16:19:55 +0300
commit0f5225b024d4bffd682aab008c35862e8fdc1865 (patch)
treea5202d5cdb071b3060975c4bd4c1c3f56c792edc /include/linux/mutex.h
parent83f06168ef15da5dc735c7ea14fae67609ed9538 (diff)
downloadlinux-0f5225b024d4bffd682aab008c35862e8fdc1865.tar.xz
locking/mutex, drm: Introduce mutex_trylock_recursive()
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>
Diffstat (limited to 'include/linux/mutex.h')
-rw-r--r--include/linux/mutex.h31
1 files changed, 31 insertions, 0 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 4d3bccabbea5..6a902f0a2148 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -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 */