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 <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>
This commit is contained in:
Jason Low
Ingo Molnar
Родитель
055ce0fd1b
Коммит
8ee62b1870
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@ -25,8 +25,8 @@ static inline void __down_read(struct rw_semaphore *sem)
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{
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long oldcount;
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#ifndef CONFIG_SMP
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oldcount = sem->count;
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sem->count += RWSEM_ACTIVE_READ_BIAS;
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oldcount = sem->count.counter;
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sem->count.counter += RWSEM_ACTIVE_READ_BIAS;
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#else
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long temp;
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__asm__ __volatile__(
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@ -52,13 +52,13 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
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{
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long old, new, res;
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res = sem->count;
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res = atomic_long_read(&sem->count);
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do {
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new = res + RWSEM_ACTIVE_READ_BIAS;
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if (new <= 0)
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break;
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old = res;
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res = cmpxchg(&sem->count, old, new);
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res = atomic_long_cmpxchg(&sem->count, old, new);
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} while (res != old);
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return res >= 0 ? 1 : 0;
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}
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@ -67,8 +67,8 @@ static inline long ___down_write(struct rw_semaphore *sem)
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{
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long oldcount;
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#ifndef CONFIG_SMP
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oldcount = sem->count;
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sem->count += RWSEM_ACTIVE_WRITE_BIAS;
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oldcount = sem->count.counter;
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sem->count.counter += RWSEM_ACTIVE_WRITE_BIAS;
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#else
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long temp;
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__asm__ __volatile__(
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@ -106,7 +106,7 @@ static inline int __down_write_killable(struct rw_semaphore *sem)
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*/
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static inline int __down_write_trylock(struct rw_semaphore *sem)
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{
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long ret = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
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long ret = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
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RWSEM_ACTIVE_WRITE_BIAS);
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if (ret == RWSEM_UNLOCKED_VALUE)
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return 1;
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@ -117,8 +117,8 @@ static inline void __up_read(struct rw_semaphore *sem)
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{
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long oldcount;
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#ifndef CONFIG_SMP
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oldcount = sem->count;
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sem->count -= RWSEM_ACTIVE_READ_BIAS;
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oldcount = sem->count.counter;
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sem->count.counter -= RWSEM_ACTIVE_READ_BIAS;
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#else
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long temp;
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__asm__ __volatile__(
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@ -142,8 +142,8 @@ static inline void __up_write(struct rw_semaphore *sem)
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{
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long count;
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#ifndef CONFIG_SMP
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sem->count -= RWSEM_ACTIVE_WRITE_BIAS;
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count = sem->count;
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sem->count.counter -= RWSEM_ACTIVE_WRITE_BIAS;
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count = sem->count.counter;
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#else
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long temp;
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__asm__ __volatile__(
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@ -171,8 +171,8 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
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{
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long oldcount;
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#ifndef CONFIG_SMP
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oldcount = sem->count;
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sem->count -= RWSEM_WAITING_BIAS;
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oldcount = sem->count.counter;
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sem->count.counter -= RWSEM_WAITING_BIAS;
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#else
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long temp;
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__asm__ __volatile__(
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@ -40,7 +40,7 @@
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static inline void
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__down_read (struct rw_semaphore *sem)
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{
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long result = ia64_fetchadd8_acq((unsigned long *)&sem->count, 1);
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long result = ia64_fetchadd8_acq((unsigned long *)&sem->count.counter, 1);
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if (result < 0)
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rwsem_down_read_failed(sem);
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@ -55,9 +55,9 @@ ___down_write (struct rw_semaphore *sem)
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long old, new;
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do {
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old = sem->count;
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old = atomic_long_read(&sem->count);
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new = old + RWSEM_ACTIVE_WRITE_BIAS;
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} while (cmpxchg_acq(&sem->count, old, new) != old);
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} while (atomic_long_cmpxchg_acquire(&sem->count, old, new) != old);
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return old;
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}
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@ -85,7 +85,7 @@ __down_write_killable (struct rw_semaphore *sem)
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static inline void
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__up_read (struct rw_semaphore *sem)
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{
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long result = ia64_fetchadd8_rel((unsigned long *)&sem->count, -1);
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long result = ia64_fetchadd8_rel((unsigned long *)&sem->count.counter, -1);
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if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
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rwsem_wake(sem);
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@ -100,9 +100,9 @@ __up_write (struct rw_semaphore *sem)
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long old, new;
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do {
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old = sem->count;
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old = atomic_long_read(&sem->count);
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new = old - RWSEM_ACTIVE_WRITE_BIAS;
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} while (cmpxchg_rel(&sem->count, old, new) != old);
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} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
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if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
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rwsem_wake(sem);
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@ -115,8 +115,8 @@ static inline int
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__down_read_trylock (struct rw_semaphore *sem)
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{
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long tmp;
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while ((tmp = sem->count) >= 0) {
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if (tmp == cmpxchg_acq(&sem->count, tmp, tmp+1)) {
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while ((tmp = atomic_long_read(&sem->count)) >= 0) {
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if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp, tmp+1)) {
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return 1;
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}
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}
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@ -129,8 +129,8 @@ __down_read_trylock (struct rw_semaphore *sem)
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static inline int
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__down_write_trylock (struct rw_semaphore *sem)
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{
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long tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE,
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RWSEM_ACTIVE_WRITE_BIAS);
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long tmp = atomic_long_cmpxchg_acquire(&sem->count,
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RWSEM_UNLOCKED_VALUE, RWSEM_ACTIVE_WRITE_BIAS);
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return tmp == RWSEM_UNLOCKED_VALUE;
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}
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@ -143,9 +143,9 @@ __downgrade_write (struct rw_semaphore *sem)
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long old, new;
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do {
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old = sem->count;
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old = atomic_long_read(&sem->count);
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new = old - RWSEM_WAITING_BIAS;
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} while (cmpxchg_rel(&sem->count, old, new) != old);
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} while (atomic_long_cmpxchg_release(&sem->count, old, new) != old);
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if (old < 0)
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rwsem_downgrade_wake(sem);
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@ -41,8 +41,8 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
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{
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long tmp;
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while ((tmp = sem->count) >= 0) {
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if (tmp == cmpxchg_acquire(&sem->count, tmp,
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while ((tmp = atomic_long_read(&sem->count)) >= 0) {
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if (tmp == atomic_long_cmpxchg_acquire(&sem->count, tmp,
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tmp + RWSEM_ACTIVE_READ_BIAS)) {
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return 1;
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}
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@ -79,7 +79,7 @@ static inline int __down_write_trylock(struct rw_semaphore *sem)
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{
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long tmp;
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tmp = cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
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tmp = atomic_long_cmpxchg_acquire(&sem->count, RWSEM_UNLOCKED_VALUE,
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RWSEM_ACTIVE_WRITE_BIAS);
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return tmp == RWSEM_UNLOCKED_VALUE;
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}
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@ -23,10 +23,11 @@ struct rw_semaphore;
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#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
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#include <linux/rwsem-spinlock.h> /* use a generic implementation */
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#define __RWSEM_INIT_COUNT(name) .count = RWSEM_UNLOCKED_VALUE
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#else
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/* All arch specific implementations share the same struct */
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struct rw_semaphore {
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long count;
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atomic_long_t count;
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struct list_head wait_list;
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raw_spinlock_t wait_lock;
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#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
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@ -54,9 +55,10 @@ extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
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/* In all implementations count != 0 means locked */
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static inline int rwsem_is_locked(struct rw_semaphore *sem)
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{
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return sem->count != 0;
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return atomic_long_read(&sem->count) != 0;
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}
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#define __RWSEM_INIT_COUNT(name) .count = ATOMIC_LONG_INIT(RWSEM_UNLOCKED_VALUE)
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#endif
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/* Common initializer macros and functions */
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@ -74,7 +76,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
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#endif
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#define __RWSEM_INITIALIZER(name) \
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{ .count = RWSEM_UNLOCKED_VALUE, \
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{ __RWSEM_INIT_COUNT(name), \
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.wait_list = LIST_HEAD_INIT((name).wait_list), \
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.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
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__RWSEM_OPT_INIT(name) \
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@ -80,7 +80,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
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debug_check_no_locks_freed((void *)sem, sizeof(*sem));
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lockdep_init_map(&sem->dep_map, name, key, 0);
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#endif
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sem->count = RWSEM_UNLOCKED_VALUE;
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atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE);
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raw_spin_lock_init(&sem->wait_lock);
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INIT_LIST_HEAD(&sem->wait_list);
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#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
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@ -153,10 +153,11 @@ __rwsem_mark_wake(struct rw_semaphore *sem,
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if (wake_type != RWSEM_WAKE_READ_OWNED) {
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adjustment = RWSEM_ACTIVE_READ_BIAS;
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try_reader_grant:
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oldcount = rwsem_atomic_update(adjustment, sem) - adjustment;
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oldcount = atomic_long_add_return(adjustment, &sem->count) - adjustment;
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if (unlikely(oldcount < RWSEM_WAITING_BIAS)) {
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/* A writer stole the lock. Undo our reader grant. */
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if (rwsem_atomic_update(-adjustment, sem) &
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if (atomic_long_sub_return(adjustment, &sem->count) &
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RWSEM_ACTIVE_MASK)
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goto out;
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/* Last active locker left. Retry waking readers. */
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@ -186,7 +187,7 @@ __rwsem_mark_wake(struct rw_semaphore *sem,
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adjustment -= RWSEM_WAITING_BIAS;
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if (adjustment)
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rwsem_atomic_add(adjustment, sem);
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atomic_long_add(adjustment, &sem->count);
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next = sem->wait_list.next;
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loop = woken;
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@ -233,7 +234,7 @@ struct rw_semaphore __sched *rwsem_down_read_failed(struct rw_semaphore *sem)
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list_add_tail(&waiter.list, &sem->wait_list);
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/* we're now waiting on the lock, but no longer actively locking */
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count = rwsem_atomic_update(adjustment, sem);
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count = atomic_long_add_return(adjustment, &sem->count);
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/* If there are no active locks, wake the front queued process(es).
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*
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@ -282,7 +283,8 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
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RWSEM_ACTIVE_WRITE_BIAS :
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RWSEM_ACTIVE_WRITE_BIAS + RWSEM_WAITING_BIAS;
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if (cmpxchg_acquire(&sem->count, RWSEM_WAITING_BIAS, count) == RWSEM_WAITING_BIAS) {
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if (atomic_long_cmpxchg_acquire(&sem->count, RWSEM_WAITING_BIAS, count)
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== RWSEM_WAITING_BIAS) {
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rwsem_set_owner(sem);
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return true;
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}
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@ -296,13 +298,13 @@ static inline bool rwsem_try_write_lock(long count, struct rw_semaphore *sem)
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*/
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static inline bool rwsem_try_write_lock_unqueued(struct rw_semaphore *sem)
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{
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long old, count = READ_ONCE(sem->count);
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long old, count = atomic_long_read(&sem->count);
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while (true) {
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if (!(count == 0 || count == RWSEM_WAITING_BIAS))
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return false;
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old = cmpxchg_acquire(&sem->count, count,
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old = atomic_long_cmpxchg_acquire(&sem->count, count,
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count + RWSEM_ACTIVE_WRITE_BIAS);
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if (old == count) {
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rwsem_set_owner(sem);
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@ -324,7 +326,7 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem)
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rcu_read_lock();
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owner = READ_ONCE(sem->owner);
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if (!owner) {
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long count = READ_ONCE(sem->count);
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long count = atomic_long_read(&sem->count);
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/*
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* If sem->owner is not set, yet we have just recently entered the
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* slowpath with the lock being active, then there is a possibility
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@ -375,7 +377,7 @@ bool rwsem_spin_on_owner(struct rw_semaphore *sem, struct task_struct *owner)
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* held by readers. Check the counter to verify the
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* state.
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*/
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count = READ_ONCE(sem->count);
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count = atomic_long_read(&sem->count);
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return (count == 0 || count == RWSEM_WAITING_BIAS);
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}
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@ -460,7 +462,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
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WAKE_Q(wake_q);
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/* undo write bias from down_write operation, stop active locking */
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count = rwsem_atomic_update(-RWSEM_ACTIVE_WRITE_BIAS, sem);
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count = atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS, &sem->count);
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/* do optimistic spinning and steal lock if possible */
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if (rwsem_optimistic_spin(sem))
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@ -483,7 +485,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
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/* we're now waiting on the lock, but no longer actively locking */
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if (waiting) {
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count = READ_ONCE(sem->count);
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count = atomic_long_read(&sem->count);
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/*
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* If there were already threads queued before us and there are
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@ -505,7 +507,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
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}
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} else
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count = rwsem_atomic_update(RWSEM_WAITING_BIAS, sem);
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count = atomic_long_add_return(RWSEM_WAITING_BIAS, &sem->count);
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/* wait until we successfully acquire the lock */
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set_current_state(state);
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@ -521,7 +523,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state)
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schedule();
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set_current_state(state);
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} while ((count = sem->count) & RWSEM_ACTIVE_MASK);
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} while ((count = atomic_long_read(&sem->count)) & RWSEM_ACTIVE_MASK);
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raw_spin_lock_irq(&sem->wait_lock);
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}
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@ -536,7 +538,7 @@ out_nolock:
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raw_spin_lock_irq(&sem->wait_lock);
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list_del(&waiter.list);
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if (list_empty(&sem->wait_list))
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rwsem_atomic_update(-RWSEM_WAITING_BIAS, sem);
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atomic_long_add(-RWSEM_WAITING_BIAS, &sem->count);
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else
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__rwsem_mark_wake(sem, RWSEM_WAKE_ANY, &wake_q);
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raw_spin_unlock_irq(&sem->wait_lock);
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