From 8ee62b1870be8e630158701632a533d0378e15b8 Mon Sep 17 00:00:00 2001 From: Jason Low Date: Fri, 3 Jun 2016 22:26:02 -0700 Subject: [PATCH] locking/rwsem: Convert sem->count to 'atomic_long_t' 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 Signed-off-by: Jason Low [ Build warning fixes on various architectures. ] Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Davidlohr Bueso Cc: Fenghua Yu Cc: Heiko Carstens Cc: Jason Low Cc: Linus Torvalds Cc: Martin Schwidefsky Cc: Paul E. McKenney Cc: Peter Hurley Cc: Terry Rudd Cc: Thomas Gleixner Cc: Tim Chen Cc: Tony Luck Cc: Waiman Long Link: http://lkml.kernel.org/r/1465017963-4839-2-git-send-email-jason.low2@hpe.com Signed-off-by: Ingo Molnar --- arch/alpha/include/asm/rwsem.h | 26 +++++++++++++------------- arch/ia64/include/asm/rwsem.h | 24 ++++++++++++------------ include/asm-generic/rwsem.h | 6 +++--- include/linux/rwsem.h | 8 +++++--- kernel/locking/rwsem-xadd.c | 32 +++++++++++++++++--------------- 5 files changed, 50 insertions(+), 46 deletions(-) diff --git a/arch/alpha/include/asm/rwsem.h b/arch/alpha/include/asm/rwsem.h index 0131a7058778..b40021aabb9f 100644 --- a/arch/alpha/include/asm/rwsem.h +++ b/arch/alpha/include/asm/rwsem.h @@ -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__( diff --git a/arch/ia64/include/asm/rwsem.h b/arch/ia64/include/asm/rwsem.h index 8b23e070b844..c5d544f188ed 100644 --- a/arch/ia64/include/asm/rwsem.h +++ b/arch/ia64/include/asm/rwsem.h @@ -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); diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h index 3fc94a046bf5..a3a93eca766c 100644 --- a/include/asm-generic/rwsem.h +++ b/include/asm-generic/rwsem.h @@ -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; } diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index d37fbb34d06f..dd1d14250340 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -23,10 +23,11 @@ struct rw_semaphore; #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK #include /* 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) \ diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index b957da7fcb19..63b40a5c62ec 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -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); -- 2.39.5