locking/rwsem: Convert sem->count to 'atomic_long_t'
authorJason Low <jason.low2@hpe.com>
Sat, 4 Jun 2016 05:26:02 +0000 (22:26 -0700)
committerIngo Molnar <mingo@kernel.org>
Wed, 8 Jun 2016 13:16:42 +0000 (15:16 +0200)
Convert the rwsem count variable to an atomic_long_t since we use it
as an atomic variable. This also allows us to remove the
rwsem_atomic_{add,update}() "abstraction" which would now be an unnecesary
level of indirection. In follow up patches, we also remove the
rwsem_atomic_{add,update}() definitions across the various architectures.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jason Low <jason.low2@hpe.com>
[ Build warning fixes on various architectures. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Terry Rudd <terry.rudd@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Waiman Long <Waiman.Long@hpe.com>
Link: http://lkml.kernel.org/r/1465017963-4839-2-git-send-email-jason.low2@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
arch/alpha/include/asm/rwsem.h
arch/ia64/include/asm/rwsem.h
include/asm-generic/rwsem.h
include/linux/rwsem.h
kernel/locking/rwsem-xadd.c

index 0131a70..b40021a 100644 (file)
@@ -25,8 +25,8 @@ static inline void __down_read(struct rw_semaphore *sem)
 {
        long oldcount;
 #ifndef        CONFIG_SMP
-       oldcount = sem->count;
-       sem->count += RWSEM_ACTIVE_READ_BIAS;
+       oldcount = sem->count.counter;
+       sem->count.counter += RWSEM_ACTIVE_READ_BIAS;
 #else
        long temp;
        __asm__ __volatile__(
@@ -52,13 +52,13 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
 {
        long old, new, res;
 
-       res = sem->count;
+       res = atomic_long_read(&sem->count);
        do {
                new = res + RWSEM_ACTIVE_READ_BIAS;
                if (new <= 0)
                        break;
                old = res;
-               res = cmpxchg(&sem->count, old, new);
+               res = atomic_long_cmpxchg(&sem->count, old, new);
        } while (res != old);
        return res >= 0 ? 1 : 0;
 }
@@ -67,8 +67,8 @@ static inline long ___down_write(struct rw_semaphore *sem)
 {
        long oldcount;
 #ifndef        CONFIG_SMP
-       oldcount = sem->count;
-       sem->count += RWSEM_ACTIVE_WRITE_BIAS;
+       oldcount = sem->count.counter;
+       sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
 #else
        long temp;
        __asm__ __volatile__(
@@ -106,7 +106,7 @@ static inline int __down_write_killable(struct rw_semaphore *sem)
  */
 static inline int __down_write_trylock(struct rw_semaphore *sem)
 {
-       long ret = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
+       long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
                           RWSEM_ACTIVE_WRITE_BIAS);
        if (ret == RWSEM_UNLOCKED_VALUE)
                return 1;
@@ -117,8 +117,8 @@ static inline void __up_read(struct rw_semaphore *sem)
 {
        long oldcount;
 #ifndef        CONFIG_SMP
-       oldcount = sem->count;
-       sem->count -= RWSEM_ACTIVE_READ_BIAS;
+       oldcount = sem->count.counter;
+       sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
 #else
        long temp;
        __asm__ __volatile__(
@@ -142,8 +142,8 @@ static inline void __up_write(struct rw_semaphore *sem)
 {
        long count;
 #ifndef        CONFIG_SMP
-       sem->count -= RWSEM_ACTIVE_WRITE_BIAS;
-       count = sem->count;
+       sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
+       count = sem->count.counter;
 #else
        long temp;
        __asm__ __volatile__(
@@ -171,8 +171,8 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
 {
        long oldcount;
 #ifndef        CONFIG_SMP
-       oldcount = sem->count;
-       sem->count -= RWSEM_WAITING_BIAS;
+       oldcount = sem->count.counter;
+       sem->count.counter -= RWSEM_WAITING_BIAS;
 #else
        long temp;
        __asm__ __volatile__(
index 8b23e07..c5d544f 100644 (file)
@@ -40,7 +40,7 @@
 static inline void
 __down_read (struct rw_semaphore *sem)
 {
-       long result = ia64_fetchadd8_acq((unsigned long *)&sem->count, 1);
+       long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1);
 
        if (result < 0)
                rwsem_down_read_failed(sem);
@@ -55,9 +55,9 @@ ___down_write (struct rw_semaphore *sem)
        long old, new;
 
        do {
-               old = sem->count;
+               old = atomic_long_read(&sem->count);
                new = old + RWSEM_ACTIVE_WRITE_BIAS;
-       } while (cmpxchg_acq(&sem->count, old, new) != old);
+       } while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old);
 
        return old;
 }
@@ -85,7 +85,7 @@ __down_write_killable (struct rw_semaphore *sem)
 static inline void
 __up_read (struct rw_semaphore *sem)
 {
-       long result = ia64_fetchadd8_rel((unsigned long *)&sem->count, -1);
+       long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1);
 
        if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
                rwsem_wake(sem);
@@ -100,9 +100,9 @@ __up_write (struct rw_semaphore *sem)
        long old, new;
 
        do {
-               old = sem->count;
+               old = atomic_long_read(&sem->count);
                new = old - RWSEM_ACTIVE_WRITE_BIAS;
-       } while (cmpxchg_rel(&sem->count, old, new) != old);
+       } while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
 
        if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
                rwsem_wake(sem);
@@ -115,8 +115,8 @@ static inline int
 __down_read_trylock (struct rw_semaphore *sem)
 {
        long tmp;
-       while ((tmp = sem->count) >= 0) {
-               if (tmp == cmpxchg_acq(&sem->count, tmp, tmp+1)) {
+       while ((tmp = atomic_long_read(&sem->count)) >= 0) {
+               if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) {
                        return 1;
                }
        }
@@ -129,8 +129,8 @@ __down_read_trylock (struct rw_semaphore *sem)
 static inline int
 __down_write_trylock (struct rw_semaphore *sem)
 {
-       long tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE,
-                             RWSEM_ACTIVE_WRITE_BIAS);
+       long tmp = atomic_long_cmpxchg_acquire(&sem->count,
+                       RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS);
        return tmp == RWSEM_UNLOCKED_VALUE;
 }
 
@@ -143,9 +143,9 @@ __downgrade_write (struct rw_semaphore *sem)
        long old, new;
 
        do {
-               old = sem->count;
+               old = atomic_long_read(&sem->count);
                new = old - RWSEM_WAITING_BIAS;
-       } while (cmpxchg_rel(&sem->count, old, new) != old);
+       } while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
 
        if (old < 0)
                rwsem_downgrade_wake(sem);
index 3fc94a0..a3a93ec 100644 (file)
@@ -41,8 +41,8 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
 {
        long tmp;
 
-       while ((tmp = sem->count) >= 0) {
-               if (tmp == cmpxchg_acquire(&sem->count, tmp,
+       while ((tmp = atomic_long_read(&sem->count)) >= 0) {
+               if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
                                   tmp + RWSEM_ACTIVE_READ_BIAS)) {
                        return 1;
                }
@@ -79,7 +79,7 @@ static inline int __down_write_trylock(struct rw_semaphore *sem)
 {
        long tmp;
 
-       tmp = cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
+       tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
                      RWSEM_ACTIVE_WRITE_BIAS);
        return tmp == RWSEM_UNLOCKED_VALUE;
 }
index d37fbb3..dd1d142 100644 (file)
@@ -23,10 +23,11 @@ struct rw_semaphore;
 
 #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
 #include <linux/rwsem-spinlock.h> /* use a generic implementation */
+#define __RWSEM_INIT_COUNT(name)       .count = RWSEM_UNLOCKED_VALUE
 #else
 /* All arch specific implementations share the same struct */
 struct rw_semaphore {
-       long count;
+       atomic_long_t count;
        struct list_head wait_list;
        raw_spinlock_t wait_lock;
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
@@ -54,9 +55,10 @@ extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
 /* In all implementations count != 0 means locked */
 static inline int rwsem_is_locked(struct rw_semaphore *sem)
 {
-       return sem->count != 0;
+       return atomic_long_read(&sem->count) != 0;
 }
 
+#define __RWSEM_INIT_COUNT(name)       .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
 #endif
 
 /* Common initializer macros and functions */
@@ -74,7 +76,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
 #endif
 
 #define __RWSEM_INITIALIZER(name)                              \
-       { .count = RWSEM_UNLOCKED_VALUE,                        \
+       { __RWSEM_INIT_COUNT(name),                             \
          .wait_list = LIST_HEAD_INIT((name).wait_list),        \
          .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
          __RWSEM_OPT_INIT(name)                                \
index b957da7..63b40a5 100644 (file)
@@ -80,7 +80,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
        debug_check_no_locks_freed((void *)sem, sizeof(*sem));
        lockdep_init_map(&sem->dep_map, name, key, 0);
 #endif
-       sem->count = RWSEM_UNLOCKED_VALUE;
+       atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE);
        raw_spin_lock_init(&sem->wait_lock);
        INIT_LIST_HEAD(&sem->wait_list);
 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
@@ -153,10 +153,11 @@ __rwsem_mark_wake(struct rw_semaphore *sem,
        if (wake_type != RWSEM_WAKE_READ_OWNED) {
                adjustment = RWSEM_ACTIVE_READ_BIAS;
  try_reader_grant:
-               oldcount = rwsem_atomic_update(adjustment, sem) - adjustment;
+               oldcount = atomic_long_add_return(adjustment, &sem->count) - adjustment;
+
                if (unlikely(oldcount < RWSEM_WAITING_BIAS)) {
                        /* A writer stole the lock. Undo our reader grant. */
-                       if (rwsem_atomic_update(-adjustment, sem) &
+                       if (atomic_long_sub_return(adjustment, &sem->count) &
                                                RWSEM_ACTIVE_MASK)
                                goto out;
                        /* Last active locker left. Retry waking readers. */
@@ -186,7 +187,7 @@ __rwsem_mark_wake(struct rw_semaphore *sem,
                adjustment -= RWSEM_WAITING_BIAS;
 
        if (adjustment)
-               rwsem_atomic_add(adjustment, sem);
+               atomic_long_add(adjustment, &sem->count);
 
        next = sem->wait_list.next;
        loop = woken;
@@ -233,7 +234,7 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
        list_add_tail(&waiter.list, &sem->wait_list);
 
        /* we're now waiting on the lock, but no longer actively locking */
-       count = rwsem_atomic_update(adjustment, sem);
+       count = atomic_long_add_return(adjustment, &sem->count);
 
        /* If there are no active locks, wake the front queued process(es).
         *
@@ -282,7 +283,8 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
                        RWSEM_ACTIVE_WRITE_BIAS :
                        RWSEM_ACTIVE_WRITE_BIAS + RWSEM_WAITING_BIAS;
 
-       if (cmpxchg_acquire(&sem->count, RWSEM_WAITING_BIAS, count) == RWSEM_WAITING_BIAS) {
+       if (atomic_long_cmpxchg_acquire(&sem->count, RWSEM_WAITING_BIAS, count)
+                                                       == RWSEM_WAITING_BIAS) {
                rwsem_set_owner(sem);
                return true;
        }
@@ -296,13 +298,13 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
  */
 static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
 {
-       long old, count = READ_ONCE(sem->count);
+       long old, count = atomic_long_read(&sem->count);
 
        while (true) {
                if (!(count == 0 || count == RWSEM_WAITING_BIAS))
                        return false;
 
-               old = cmpxchg_acquire(&sem->count, count,
+               old = atomic_long_cmpxchg_acquire(&sem->count, count,
                                      count + RWSEM_ACTIVE_WRITE_BIAS);
                if (old == count) {
                        rwsem_set_owner(sem);
@@ -324,7 +326,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
        rcu_read_lock();
        owner = READ_ONCE(sem->owner);
        if (!owner) {
-               long count = READ_ONCE(sem->count);
+               long count = atomic_long_read(&sem->count);
                /*
                 * If sem->owner is not set, yet we have just recently entered the
                 * slowpath with the lock being active, then there is a possibility
@@ -375,7 +377,7 @@ bool rwsem_spin_on_owner(struct rw_semaphore *sem, struct task_struct *owner)
         * held by readers. Check the counter to verify the
         * state.
         */
-       count = READ_ONCE(sem->count);
+       count = atomic_long_read(&sem->count);
        return (count == 0 || count == RWSEM_WAITING_BIAS);
 }
 
@@ -460,7 +462,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
        WAKE_Q(wake_q);
 
        /* undo write bias from down_write operation, stop active locking */
-       count = rwsem_atomic_update(-RWSEM_ACTIVE_WRITE_BIAS, sem);
+       count = atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS, &sem->count);
 
        /* do optimistic spinning and steal lock if possible */
        if (rwsem_optimistic_spin(sem))
@@ -483,7 +485,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
 
        /* we're now waiting on the lock, but no longer actively locking */
        if (waiting) {
-               count = READ_ONCE(sem->count);
+               count = atomic_long_read(&sem->count);
 
                /*
                 * If there were already threads queued before us and there are
@@ -505,7 +507,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
                }
 
        } else
-               count = rwsem_atomic_update(RWSEM_WAITING_BIAS, sem);
+               count = atomic_long_add_return(RWSEM_WAITING_BIAS, &sem->count);
 
        /* wait until we successfully acquire the lock */
        set_current_state(state);
@@ -521,7 +523,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
 
                        schedule();
                        set_current_state(state);
-               } while ((count = sem->count) & RWSEM_ACTIVE_MASK);
+               } while ((count = atomic_long_read(&sem->count)) & RWSEM_ACTIVE_MASK);
 
                raw_spin_lock_irq(&sem->wait_lock);
        }
@@ -536,7 +538,7 @@ out_nolock:
        raw_spin_lock_irq(&sem->wait_lock);
        list_del(&waiter.list);
        if (list_empty(&sem->wait_list))
-               rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem);
+               atomic_long_add(-RWSEM_WAITING_BIAS, &sem->count);
        else
                __rwsem_mark_wake(sem, RWSEM_WAKE_ANY, &wake_q);
        raw_spin_unlock_irq(&sem->wait_lock);