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

Browse source 
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
This commit is contained in:
Linus Torvalds 2014-07-19 06:27:55 -10:00
commit d057190925
19 changed files with 154 additions and 86 deletions
Download patch file Download diff file Expand all files Collapse all files

4
include/linux/mutex.h
View file

@ -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;

27
include/linux/osq_lock.h Normal file
View file

@ -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

8
include/linux/rwsem-spinlock.h
View file

@ -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

34
include/linux/rwsem.h
View file

@ -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)