Commit-ID: 0f5225b024d4bffd682aab008c35862e8fdc1865
Gitweb: http://git.kernel.org/tip/0f5225b024d4bffd682aab008c35862e8fdc1865
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 7 Oct 2016 17:43:51 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 15 Nov 2016 14:19:55 +0100
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@xxxxxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Ding Tianhong <dingtianhong@xxxxxxxxxx>
Cc: Imre Deak <imre.deak@xxxxxxxxx>
Cc: Jason Low <jason.low2@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Terry Rudd <terry.rudd@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
Cc: Will Deacon <Will.Deacon@xxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_shrinker.c | 15 ++++++++++++---
drivers/gpu/drm/msm/msm_gem_shrinker.c | 16 ++++++++++++----
include/linux/mutex.h | 31 +++++++++++++++++++++++++++++++
scripts/checkpatch.pl | 6 ++++++
4 files changed, 61 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index e9bd2a8..c450076 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -227,11 +227,20 @@ unsigned long i915_gem_shrink_all(struct drm_i915_private *dev_priv)
static bool i915_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
{
- if (!mutex_trylock(&dev->struct_mutex))
+ switch (mutex_trylock_recursive(&dev->struct_mutex)) {
+ case MUTEX_TRYLOCK_FAILED:
return false;
- *unlock = true;
- return true;
+ case MUTEX_TRYLOCK_SUCCESS:
+ *unlock = true;
+ return true;
+
+ case MUTEX_TRYLOCK_RECURSIVE:
+ *unlock = false;
+ return true;
+ }
+
+ BUG();
}
static unsigned long
diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
index 6d2e885..b77bca7 100644
--- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
+++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
@@ -20,13 +20,21 @@
static bool msm_gem_shrinker_lock(struct drm_device *dev, bool *unlock)
{
- if (!mutex_trylock(&dev->struct_mutex))
+ switch (mutex_trylock_recursive(&dev->struct_mutex)) {
+ case MUTEX_TRYLOCK_FAILED:
return false;
- *unlock = true;
- return true;
-}
+ case MUTEX_TRYLOCK_SUCCESS:
+ *unlock = true;
+ return true;
+
+ case MUTEX_TRYLOCK_RECURSIVE:
+ *unlock = false;
+ return true;
+ }
+ BUG();
+}
static unsigned long
msm_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 4d3bcca..6a902f0 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 */
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index a8368d1..23f462f6 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6076,6 +6076,12 @@ sub process {
}
}
+# check for mutex_trylock_recursive usage
+ if ($line =~ /mutex_trylock_recursive/) {
+ ERROR("LOCKING",
+ "recursive locking is bad, do not use this ever.\n" . $herecurr);
+ }
+
# check for lockdep_set_novalidate_class
if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
$line =~ /__lockdep_no_validate__\s*\)/ ) {
--
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