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authorLinus Torvalds <torvalds@linux-foundation.org>2014-07-19 20:27:55 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-07-19 20:27:55 +0400
commitd057190925d994b808e1d07e6c76b90a32caac77 (patch)
tree1f2d104f879435881d77f0d8d1e48c3224264d53 /include
parentd1743b810d7a306d1dd837e086d18124bc38b575 (diff)
parent9de8033f1bbcce5ed23fe5da9ca1a5060207f7ed (diff)
downloadlinux-d057190925d994b808e1d07e6c76b90a32caac77.tar.xz
Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner: "The locking department delivers: - A rather large and intrusive bundle of fixes to address serious performance regressions introduced by the new rwsem / mcs technology. Simpler solutions have been discussed, but they would have been ugly bandaids with more risk than doing the right thing. - Make the rwsem spin on owner technology opt-in for architectures and enable it only on the known to work ones. - A few fixes to the lockdep userspace library" * 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER locking/mutex: Disable optimistic spinning on some architectures locking/rwsem: Reduce the size of struct rw_semaphore locking/rwsem: Rename 'activity' to 'count' locking/spinlocks/mcs: Micro-optimize osq_unlock() locking/spinlocks/mcs: Introduce and use init macro and function for osq locks locking/spinlocks/mcs: Convert osq lock to atomic_t to reduce overhead locking/spinlocks/mcs: Rename optimistic_spin_queue() to optimistic_spin_node() locking/rwsem: Allow conservative optimistic spinning when readers have lock tools/liblockdep: Account for bitfield changes in lockdeps lock_acquire tools/liblockdep: Remove debug print left over from development tools/liblockdep: Fix comparison of a boolean value with a value of 2
Diffstat (limited to 'include')
-rw-r--r--include/linux/mutex.h4
-rw-r--r--include/linux/osq_lock.h27
-rw-r--r--include/linux/rwsem-spinlock.h8
-rw-r--r--include/linux/rwsem.h34
4 files changed, 49 insertions, 24 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 11692dea18aa..42aa9b9ecd5f 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -17,6 +17,7 @@
#include <linux/lockdep.h>
#include <linux/atomic.h>
#include <asm/processor.h>
+#include <linux/osq_lock.h>
/*
* Simple, straightforward mutexes with strict semantics:
@@ -46,7 +47,6 @@
* - detects multi-task circular deadlocks and prints out all affected
* locks and tasks (and only those tasks)
*/
-struct optimistic_spin_queue;
struct mutex {
/* 1: unlocked, 0: locked, negative: locked, possible waiters */
atomic_t count;
@@ -56,7 +56,7 @@ struct mutex {
struct task_struct *owner;
#endif
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
- struct optimistic_spin_queue *osq; /* Spinner MCS lock */
+ struct optimistic_spin_queue osq; /* Spinner MCS lock */
#endif
#ifdef CONFIG_DEBUG_MUTEXES
const char *name;
diff --git a/include/linux/osq_lock.h b/include/linux/osq_lock.h
new file mode 100644
index 000000000000..90230d5811c5
--- /dev/null
+++ b/include/linux/osq_lock.h
@@ -0,0 +1,27 @@
+#ifndef __LINUX_OSQ_LOCK_H
+#define __LINUX_OSQ_LOCK_H
+
+/*
+ * An MCS like lock especially tailored for optimistic spinning for sleeping
+ * lock implementations (mutex, rwsem, etc).
+ */
+
+#define OSQ_UNLOCKED_VAL (0)
+
+struct optimistic_spin_queue {
+ /*
+ * Stores an encoded value of the CPU # of the tail node in the queue.
+ * If the queue is empty, then it's set to OSQ_UNLOCKED_VAL.
+ */
+ atomic_t tail;
+};
+
+/* Init macro and function. */
+#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
+
+static inline void osq_lock_init(struct optimistic_spin_queue *lock)
+{
+ atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);
+}
+
+#endif
diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
index d5b13bc07a0b..561e8615528d 100644
--- a/include/linux/rwsem-spinlock.h
+++ b/include/linux/rwsem-spinlock.h
@@ -15,13 +15,13 @@
#ifdef __KERNEL__
/*
* the rw-semaphore definition
- * - if activity is 0 then there are no active readers or writers
- * - if activity is +ve then that is the number of active readers
- * - if activity is -1 then there is one active writer
+ * - if count is 0 then there are no active readers or writers
+ * - if count is +ve then that is the number of active readers
+ * - if count is -1 then there is one active writer
* - if wait_list is not empty, then there are processes waiting for the semaphore
*/
struct rw_semaphore {
- __s32 activity;
+ __s32 count;
raw_spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 8d79708146aa..035d3c57fc8a 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -13,10 +13,11 @@
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/spinlock.h>
-
#include <linux/atomic.h>
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+#include <linux/osq_lock.h>
+#endif
-struct optimistic_spin_queue;
struct rw_semaphore;
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
@@ -25,15 +26,15 @@ struct rw_semaphore;
/* All arch specific implementations share the same struct */
struct rw_semaphore {
long count;
- raw_spinlock_t wait_lock;
struct list_head wait_list;
-#ifdef CONFIG_SMP
+ raw_spinlock_t wait_lock;
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+ struct optimistic_spin_queue osq; /* spinner MCS lock */
/*
* Write owner. Used as a speculative check to see
* if the owner is running on the cpu.
*/
struct task_struct *owner;
- struct optimistic_spin_queue *osq; /* spinner MCS lock */
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
@@ -64,22 +65,19 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif
-#if defined(CONFIG_SMP) && !defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
-#define __RWSEM_INITIALIZER(name) \
- { RWSEM_UNLOCKED_VALUE, \
- __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock), \
- LIST_HEAD_INIT((name).wait_list), \
- NULL, /* owner */ \
- NULL /* mcs lock */ \
- __RWSEM_DEP_MAP_INIT(name) }
+#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
+#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL
#else
-#define __RWSEM_INITIALIZER(name) \
- { RWSEM_UNLOCKED_VALUE, \
- __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock), \
- LIST_HEAD_INIT((name).wait_list) \
- __RWSEM_DEP_MAP_INIT(name) }
+#define __RWSEM_OPT_INIT(lockname)
#endif
+#define __RWSEM_INITIALIZER(name) \
+ { .count = RWSEM_UNLOCKED_VALUE, \
+ .wait_list = LIST_HEAD_INIT((name).wait_list), \
+ .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
+ __RWSEM_OPT_INIT(name) \
+ __RWSEM_DEP_MAP_INIT(name) }
+
#define DECLARE_RWSEM(name) \
struct rw_semaphore name = __RWSEM_INITIALIZER(name)