diff options
| -rw-r--r-- | include/asm-generic/qrwlock.h | 23 | ||||
| -rw-r--r-- | include/asm-generic/qrwlock_types.h | 8 | ||||
| -rw-r--r-- | kernel/locking/qrwlock.c | 20 |
3 files changed, 14 insertions, 37 deletions
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h index c716b02e8fd7..0f7062bd55e5 100644 --- a/include/asm-generic/qrwlock.h +++ b/include/asm-generic/qrwlock.h @@ -26,24 +26,11 @@ /* * Writer states & reader shift and bias. - * - * | +0 | +1 | +2 | +3 | - * ----+----+----+----+----+ - * LE | 78 | 56 | 34 | 12 | 0x12345678 - * ----+----+----+----+----+ - * | wr | rd | - * +----+----+----+----+ - * - * ----+----+----+----+----+ - * BE | 12 | 34 | 56 | 78 | 0x12345678 - * ----+----+----+----+----+ - * | rd | wr | - * +----+----+----+----+ */ -#define _QW_WAITING 1 /* A writer is waiting */ -#define _QW_LOCKED 0xff /* A writer holds the lock */ -#define _QW_WMASK 0xff /* Writer mask */ -#define _QR_SHIFT 8 /* Reader count shift */ +#define _QW_WAITING 0x100 /* A writer is waiting */ +#define _QW_LOCKED 0x0ff /* A writer holds the lock */ +#define _QW_WMASK 0x1ff /* Writer mask */ +#define _QR_SHIFT 9 /* Reader count shift */ #define _QR_BIAS (1U << _QR_SHIFT) /* @@ -134,7 +121,7 @@ static inline void queued_read_unlock(struct qrwlock *lock) */ static inline void queued_write_unlock(struct qrwlock *lock) { - smp_store_release(&lock->wmode, 0); + smp_store_release(&lock->wlocked, 0); } /* diff --git a/include/asm-generic/qrwlock_types.h b/include/asm-generic/qrwlock_types.h index 507f2dc51bba..8af752acbdc0 100644 --- a/include/asm-generic/qrwlock_types.h +++ b/include/asm-generic/qrwlock_types.h @@ -13,11 +13,11 @@ typedef struct qrwlock { atomic_t cnts; struct { #ifdef __LITTLE_ENDIAN - u8 wmode; /* Writer mode */ - u8 rcnts[3]; /* Reader counts */ + u8 wlocked; /* Locked for write? */ + u8 __lstate[3]; #else - u8 rcnts[3]; /* Reader counts */ - u8 wmode; /* Writer mode */ + u8 __lstate[3]; + u8 wlocked; /* Locked for write? */ #endif }; }; diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c index 5825e0fc1a8e..c7471c3fb798 100644 --- a/kernel/locking/qrwlock.c +++ b/kernel/locking/qrwlock.c @@ -39,8 +39,7 @@ void queued_read_lock_slowpath(struct qrwlock *lock) * so spin with ACQUIRE semantics until the lock is available * without waiting in the queue. */ - atomic_cond_read_acquire(&lock->cnts, (VAL & _QW_WMASK) - != _QW_LOCKED); + atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED)); return; } atomic_sub(_QR_BIAS, &lock->cnts); @@ -56,7 +55,7 @@ void queued_read_lock_slowpath(struct qrwlock *lock) * that accesses can't leak upwards out of our subsequent critical * section in the case that the lock is currently held for write. */ - atomic_cond_read_acquire(&lock->cnts, (VAL & _QW_WMASK) != _QW_LOCKED); + atomic_cond_read_acquire(&lock->cnts, !(VAL & _QW_LOCKED)); /* * Signal the next one in queue to become queue head @@ -79,19 +78,10 @@ void queued_write_lock_slowpath(struct qrwlock *lock) (atomic_cmpxchg_acquire(&lock->cnts, 0, _QW_LOCKED) == 0)) goto unlock; - /* - * Set the waiting flag to notify readers that a writer is pending, - * or wait for a previous writer to go away. - */ - for (;;) { - if (!READ_ONCE(lock->wmode) && - (cmpxchg_relaxed(&lock->wmode, 0, _QW_WAITING) == 0)) - break; - - cpu_relax(); - } + /* Set the waiting flag to notify readers that a writer is pending */ + atomic_add(_QW_WAITING, &lock->cnts); - /* When no more readers, set the locked flag */ + /* When no more readers or writers, set the locked flag */ do { atomic_cond_read_acquire(&lock->cnts, VAL == _QW_WAITING); } while (atomic_cmpxchg_relaxed(&lock->cnts, _QW_WAITING, |