Commit 8308756f authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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

Pull core locking updates from Ingo Molnar:
 "The main changes are:

   - mutex, completions and rtmutex micro-optimizations
   - lock debugging fix
   - various cleanups in the MCS and the futex code"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rtmutex: Optimize setting task running after being blocked
  locking/rwsem: Use task->state helpers
  sched/completion: Add lock-free checking of the blocking case
  sched/completion: Remove unnecessary ->wait.lock serialization when reading completion state
  locking/mutex: Explicitly mark task as running after wakeup
  futex: Fix argument handling in futex_lock_pi() calls
  doc: Fix misnamed FUTEX_CMP_REQUEUE_PI op constants
  locking/Documentation: Update code path
  softirq/preempt: Add missing current->preempt_disable_ip update
  locking/osq: No need for load/acquire when acquire-polling
  locking/mcs: Better differentiate between MCS variants
  locking/mutex: Introduce ww_mutex_set_context_slowpath()
  locking/mutex: Move MCS related comments to proper location
  locking/mutex: Checking the stamp is WW only
parents 23e8fe2e afffc6c1

Documentation/futex-requeue-pi.txt

+4 −4
Original line number Diff line number Diff line
@@ -98,7 +98,7 @@ rt_mutex_start_proxy_lock() and rt_mutex_finish_proxy_lock(), which 
allow the requeue code to acquire an uncontended rt_mutex on behalf

of the waiter and to enqueue the waiter on a contended rt_mutex.

Two new system calls provide the kernel<->user interface to

requeue_pi: FUTEX_WAIT_REQUEUE_PI and FUTEX_REQUEUE_CMP_PI.

requeue_pi: FUTEX_WAIT_REQUEUE_PI and FUTEX_CMP_REQUEUE_PI.



FUTEX_WAIT_REQUEUE_PI is called by the waiter (pthread_cond_wait()

and pthread_cond_timedwait()) to block on the initial futex and wait
@@ -107,7 +107,7 @@ result of a high-speed collision between futex_wait() and 
futex_lock_pi(), with some extra logic to check for the additional

wake-up scenarios.



FUTEX_REQUEUE_CMP_PI is called by the waker

FUTEX_CMP_REQUEUE_PI is called by the waker

(pthread_cond_broadcast() and pthread_cond_signal()) to requeue and

possibly wake the waiting tasks. Internally, this system call is

still handled by futex_requeue (by passing requeue_pi=1).  Before
@@ -120,12 +120,12 @@ task as a waiter on the underlying rt_mutex. It is possible that 
the lock can be acquired at this stage as well, if so, the next

waiter is woken to finish the acquisition of the lock.



FUTEX_REQUEUE_PI accepts nr_wake and nr_requeue as arguments, but

FUTEX_CMP_REQUEUE_PI accepts nr_wake and nr_requeue as arguments, but

their sum is all that really matters.  futex_requeue() will wake or

requeue up to nr_wake + nr_requeue tasks.  It will wake only as many

tasks as it can acquire the lock for, which in the majority of cases

should be 0 as good programming practice dictates that the caller of

either pthread_cond_broadcast() or pthread_cond_signal() acquire the

mutex prior to making the call. FUTEX_REQUEUE_PI requires that

mutex prior to making the call. FUTEX_CMP_REQUEUE_PI requires that

nr_wake=1.  nr_requeue should be INT_MAX for broadcast and 0 for

signal.

Documentation/locking/lockdep-design.txt

+1 −1
Original line number Diff line number Diff line
@@ -34,7 +34,7 @@ The validator tracks lock-class usage history into 4n + 1 separate state bits: 
- 'ever held with STATE enabled'

- 'ever held as readlock with STATE enabled'



Where STATE can be either one of (kernel/lockdep_states.h)

Where STATE can be either one of (kernel/locking/lockdep_states.h)

 - hardirq

 - softirq

 - reclaim_fs

include/linux/osq_lock.h

+10 −2
Original line number Diff line number Diff line
@@ -5,8 +5,11 @@ 
 * An MCS like lock especially tailored for optimistic spinning for sleeping

 * lock implementations (mutex, rwsem, etc).

 */



#define OSQ_UNLOCKED_VAL (0)

struct optimistic_spin_node {

	struct optimistic_spin_node *next, *prev;

	int locked; /* 1 if lock acquired */

	int cpu; /* encoded CPU # + 1 value */

};



struct optimistic_spin_queue {

	/*
@@ -16,6 +19,8 @@ struct optimistic_spin_queue { 
	atomic_t tail;

};



#define OSQ_UNLOCKED_VAL (0)



/* Init macro and function. */

#define OSQ_LOCK_UNLOCKED { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }
@@ -24,4 +29,7 @@ static inline void osq_lock_init(struct optimistic_spin_queue *lock) 
	atomic_set(&lock->tail, OSQ_UNLOCKED_VAL);

}



extern bool osq_lock(struct optimistic_spin_queue *lock);

extern void osq_unlock(struct optimistic_spin_queue *lock);



#endif

kernel/Kconfig.locks

+4 −0
Original line number Diff line number Diff line
@@ -231,6 +231,10 @@ config RWSEM_SPIN_ON_OWNER 
       def_bool y

       depends on SMP && RWSEM_XCHGADD_ALGORITHM && ARCH_SUPPORTS_ATOMIC_RMW



config LOCK_SPIN_ON_OWNER

       def_bool y

       depends on MUTEX_SPIN_ON_OWNER || RWSEM_SPIN_ON_OWNER



config ARCH_USE_QUEUE_RWLOCK

	bool

kernel/futex.c

+3 −3
Original line number Diff line number Diff line
@@ -2258,7 +2258,7 @@ static long futex_wait_restart(struct restart_block *restart) 
 * if there are waiters then it will block, it does PI, etc. (Due to

 * races the kernel might see a 0 value of the futex too.)

 */

static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, int detect,

static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,

			 ktime_t *time, int trylock)

{

	struct hrtimer_sleeper timeout, *to = NULL;
@@ -2953,11 +2953,11 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, 
	case FUTEX_WAKE_OP:

		return futex_wake_op(uaddr, flags, uaddr2, val, val2, val3);

	case FUTEX_LOCK_PI:

		return futex_lock_pi(uaddr, flags, val, timeout, 0);

		return futex_lock_pi(uaddr, flags, timeout, 0);

	case FUTEX_UNLOCK_PI:

		return futex_unlock_pi(uaddr, flags);

	case FUTEX_TRYLOCK_PI:

		return futex_lock_pi(uaddr, flags, 0, timeout, 1);

		return futex_lock_pi(uaddr, flags, NULL, 1);

	case FUTEX_WAIT_REQUEUE_PI:

		val3 = FUTEX_BITSET_MATCH_ANY;

		return futex_wait_requeue_pi(uaddr, flags, val, timeout, val3,

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