Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

Pull locking fixes from Ingo Molnar:
 "Spinlock performance regression fix, plus documentation fixes"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/static_keys: Fix up the static keys documentation
  locking/qspinlock/x86: Only emit the test-and-set fallback when building guest support
  locking/qspinlock/x86: Fix performance regression under unaccelerated VMs
  locking/static_keys: Fix a silly typo

diff --git a/Documentation/static-keys.txt b/Documentation/static-keys.txt
index f4cb0b2d5cd79048c51cf7b89f803561c2070e28..477927becacba69ee4bdea2203dd796979d14449 100644 (file)
--- a/Documentation/static-keys.txt
+++ b/Documentation/static-keys.txt
@@ -15,8 +15,8 @@ The updated API replacements are:
 
 DEFINE_STATIC_KEY_TRUE(key);
 DEFINE_STATIC_KEY_FALSE(key);
-static_key_likely()
-statick_key_unlikely()
+static_branch_likely()
+static_branch_unlikely()
 
 0) Abstract
 

diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index 9d51fae1cba345e5cf01387a6c16207a6b5be872..eaba0807603009e6ed1612a7049bb35bafeaf31e 100644 (file)
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -39,18 +39,27 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
 }
 #endif
 
-#define virt_queued_spin_lock virt_queued_spin_lock
-
-static inline bool virt_queued_spin_lock(struct qspinlock *lock)
+#ifdef CONFIG_PARAVIRT
+#define virt_spin_lock virt_spin_lock
+static inline bool virt_spin_lock(struct qspinlock *lock)
 {
        if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
                return false;
 
-       while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0)
-               cpu_relax();
+       /*
+        * On hypervisors without PARAVIRT_SPINLOCKS support we fall
+        * back to a Test-and-Set spinlock, because fair locks have
+        * horrible lock 'holder' preemption issues.
+        */
+
+       do {
+               while (atomic_read(&lock->val) != 0)
+                       cpu_relax();
+       } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
 
        return true;
 }
+#endif /* CONFIG_PARAVIRT */
 
 #include <asm-generic/qspinlock.h>
 

diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h
index 83bfb87f5bf18e92ea794dd3ca3afec1b1ba6f11..e2aadbc7151f4cd69b8745e80a0af403257f1678 100644 (file)
--- a/include/asm-generic/qspinlock.h
+++ b/include/asm-generic/qspinlock.h
@@ -111,8 +111,8 @@ static inline void queued_spin_unlock_wait(struct qspinlock *lock)
                cpu_relax();
 }
 
-#ifndef virt_queued_spin_lock
-static __always_inline bool virt_queued_spin_lock(struct qspinlock *lock)
+#ifndef virt_spin_lock
+static __always_inline bool virt_spin_lock(struct qspinlock *lock)
 {
        return false;
 }

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 7f653e8f66900049c358ed4907fab8121047dd91..f1094238ab2a0f0fddeb40e3c7aadde7c2a89015 100644 (file)
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -21,8 +21,8 @@
  *
  * DEFINE_STATIC_KEY_TRUE(key);
  * DEFINE_STATIC_KEY_FALSE(key);
- * static_key_likely()
- * statick_key_unlikely()
+ * static_branch_likely()
+ * static_branch_unlikely()
  *
  * Jump labels provide an interface to generate dynamic branches using
  * self-modifying code. Assuming toolchain and architecture support, if we
@@ -45,12 +45,10 @@
  * statement, setting the key to true requires us to patch in a jump
  * to the out-of-line of true branch.
  *
- * In addtion to static_branch_{enable,disable}, we can also reference count
+ * In addition to static_branch_{enable,disable}, we can also reference count
  * the key or branch direction via static_branch_{inc,dec}. Thus,
  * static_branch_inc() can be thought of as a 'make more true' and
- * static_branch_dec() as a 'make more false'. The inc()/dec()
- * interface is meant to be used exclusively from the inc()/dec() for a given
- * key.
+ * static_branch_dec() as a 'make more false'.
  *
  * Since this relies on modifying code, the branch modifying functions
  * must be considered absolute slow paths (machine wide synchronization etc.).

diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 337c8818541d339aac3fd1e3e6af32dac6dff4c9..87e9ce6a63c5d0e78a17977e2e9271ffaf0bb946 100644 (file)
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -289,7 +289,7 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
        if (pv_enabled())
                goto queue;
 
-       if (virt_queued_spin_lock(lock))
+       if (virt_spin_lock(lock))
                return;
 
        /*