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authorLinus Torvalds <torvalds@linux-foundation.org>2015-09-17 08:45:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-17 08:45:23 -0700
commit9786cff38a31c452e32fd2f9a479dd7d19d91712 (patch)
tree1197c2e7a4e8973d19919f54f342fba6067488e2
parent1b3dfde386b7c72b8f5430dc40eee538eb40c948 (diff)
parent1975dbc276c6ab62230cf4f9df5ddc9ff0e0e473 (diff)
downloadlinux-stericsson-9786cff38a31c452e32fd2f9a479dd7d19d91712.tar.gz
Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
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
-rw-r--r--Documentation/static-keys.txt4
-rw-r--r--arch/x86/include/asm/qspinlock.h19
-rw-r--r--include/asm-generic/qspinlock.h4
-rw-r--r--include/linux/jump_label.h10
-rw-r--r--kernel/locking/qspinlock.c2
5 files changed, 23 insertions, 16 deletions
diff --git a/Documentation/static-keys.txt b/Documentation/static-keys.txt
index f4cb0b2d5cd7..477927becacb 100644
--- 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 9d51fae1cba3..eaba08076030 100644
--- 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 83bfb87f5bf1..e2aadbc7151f 100644
--- 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 7f653e8f6690..f1094238ab2a 100644
--- 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 337c8818541d..87e9ce6a63c5 100644
--- 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;
/*