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>
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@ -227,11 +227,20 @@ unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
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static bool i915_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
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{
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if (!mutex_trylock(&dev->struct_mutex))
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switch (mutex_trylock_recursive(&dev->struct_mutex)) {
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case MUTEX_TRYLOCK_FAILED:
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return false;
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*unlock = true;
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return true;
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case MUTEX_TRYLOCK_SUCCESS:
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*unlock = true;
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return true;
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case MUTEX_TRYLOCK_RECURSIVE:
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*unlock = false;
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return true;
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}
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BUG();
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}
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static unsigned long
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@ -20,13 +20,21 @@
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static bool msm_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
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{
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if (!mutex_trylock(&dev->struct_mutex))
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switch (mutex_trylock_recursive(&dev->struct_mutex)) {
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case MUTEX_TRYLOCK_FAILED:
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return false;
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*unlock = true;
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return true;
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}
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case MUTEX_TRYLOCK_SUCCESS:
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*unlock = true;
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return true;
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case MUTEX_TRYLOCK_RECURSIVE:
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*unlock = false;
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return true;
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}
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BUG();
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}
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static unsigned long
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msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
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@ -189,4 +189,35 @@ extern void mutex_unlock(struct mutex *lock);
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extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
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/*
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* These values are chosen such that FAIL and SUCCESS match the
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* values of the regular mutex_trylock().
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*/
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enum mutex_trylock_recursive_enum {
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MUTEX_TRYLOCK_FAILED = 0,
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MUTEX_TRYLOCK_SUCCESS = 1,
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MUTEX_TRYLOCK_RECURSIVE,
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};
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/**
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* mutex_trylock_recursive - trylock variant that allows recursive locking
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* @lock: mutex to be locked
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*
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* This function should not be used, _ever_. It is purely for hysterical GEM
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* raisins, and once those are gone this will be removed.
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*
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* Returns:
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* MUTEX_TRYLOCK_FAILED - trylock failed,
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* MUTEX_TRYLOCK_SUCCESS - lock acquired,
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* MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
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*/
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static inline __deprecated __must_check enum mutex_trylock_recursive_enum
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mutex_trylock_recursive(struct mutex *lock)
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{
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if (unlikely(__mutex_owner(lock) == current))
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return MUTEX_TRYLOCK_RECURSIVE;
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return mutex_trylock(lock);
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}
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#endif /* __LINUX_MUTEX_H */
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@ -6076,6 +6076,12 @@ sub process {
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}
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}
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# check for mutex_trylock_recursive usage
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if ($line =~ /mutex_trylock_recursive/) {
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ERROR("LOCKING",
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"recursive locking is bad, do not use this ever.\n" . $herecurr);
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}
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# check for lockdep_set_novalidate_class
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if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
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$line =~ /__lockdep_no_validate__\s*\)/ ) {
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