diff options
Diffstat (limited to 'arch/tile')
-rw-r--r-- | arch/tile/include/asm/spinlock_32.h | 83 | ||||
-rw-r--r-- | arch/tile/lib/spinlock_32.c | 161 |
2 files changed, 103 insertions, 141 deletions
diff --git a/arch/tile/include/asm/spinlock_32.h b/arch/tile/include/asm/spinlock_32.h index 88efdde8dd2b..a8f2c6e31a87 100644 --- a/arch/tile/include/asm/spinlock_32.h +++ b/arch/tile/include/asm/spinlock_32.h @@ -78,13 +78,6 @@ void arch_spin_unlock_wait(arch_spinlock_t *lock); #define _RD_COUNT_SHIFT 24 #define _RD_COUNT_WIDTH 8 -/* Internal functions; do not use. */ -void arch_read_lock_slow(arch_rwlock_t *, u32); -int arch_read_trylock_slow(arch_rwlock_t *); -void arch_read_unlock_slow(arch_rwlock_t *); -void arch_write_lock_slow(arch_rwlock_t *, u32); -void arch_write_unlock_slow(arch_rwlock_t *, u32); - /** * arch_read_can_lock() - would read_trylock() succeed? */ @@ -104,94 +97,32 @@ static inline int arch_write_can_lock(arch_rwlock_t *rwlock) /** * arch_read_lock() - acquire a read lock. */ -static inline void arch_read_lock(arch_rwlock_t *rwlock) -{ - u32 val = __insn_tns((int *)&rwlock->lock); - if (unlikely(val << _RD_COUNT_WIDTH)) { - arch_read_lock_slow(rwlock, val); - return; - } - rwlock->lock = val + (1 << _RD_COUNT_SHIFT); -} +void arch_read_lock(arch_rwlock_t *rwlock); /** - * arch_read_lock() - acquire a write lock. + * arch_write_lock() - acquire a write lock. */ -static inline void arch_write_lock(arch_rwlock_t *rwlock) -{ - u32 val = __insn_tns((int *)&rwlock->lock); - if (unlikely(val != 0)) { - arch_write_lock_slow(rwlock, val); - return; - } - rwlock->lock = 1 << _WR_NEXT_SHIFT; -} +void arch_write_lock(arch_rwlock_t *rwlock); /** * arch_read_trylock() - try to acquire a read lock. */ -static inline int arch_read_trylock(arch_rwlock_t *rwlock) -{ - int locked; - u32 val = __insn_tns((int *)&rwlock->lock); - if (unlikely(val & 1)) - return arch_read_trylock_slow(rwlock); - locked = (val << _RD_COUNT_WIDTH) == 0; - rwlock->lock = val + (locked << _RD_COUNT_SHIFT); - return locked; -} +int arch_read_trylock(arch_rwlock_t *rwlock); /** * arch_write_trylock() - try to acquire a write lock. */ -static inline int arch_write_trylock(arch_rwlock_t *rwlock) -{ - u32 val = __insn_tns((int *)&rwlock->lock); - - /* - * If a tns is in progress, or there's a waiting or active locker, - * or active readers, we can't take the lock, so give up. - */ - if (unlikely(val != 0)) { - if (!(val & 1)) - rwlock->lock = val; - return 0; - } - - /* Set the "next" field to mark it locked. */ - rwlock->lock = 1 << _WR_NEXT_SHIFT; - return 1; -} +int arch_write_trylock(arch_rwlock_t *rwlock); /** * arch_read_unlock() - release a read lock. */ -static inline void arch_read_unlock(arch_rwlock_t *rwlock) -{ - u32 val; - mb(); /* guarantee anything modified under the lock is visible */ - val = __insn_tns((int *)&rwlock->lock); - if (unlikely(val & 1)) { - arch_read_unlock_slow(rwlock); - return; - } - rwlock->lock = val - (1 << _RD_COUNT_SHIFT); -} +void arch_read_unlock(arch_rwlock_t *rwlock); /** * arch_write_unlock() - release a write lock. */ -static inline void arch_write_unlock(arch_rwlock_t *rwlock) -{ - u32 val; - mb(); /* guarantee anything modified under the lock is visible */ - val = __insn_tns((int *)&rwlock->lock); - if (unlikely(val != (1 << _WR_NEXT_SHIFT))) { - arch_write_unlock_slow(rwlock, val); - return; - } - rwlock->lock = 0; -} +void arch_write_unlock(arch_rwlock_t *rwlock); #define arch_read_lock_flags(lock, flags) arch_read_lock(lock) #define arch_write_lock_flags(lock, flags) arch_write_lock(lock) diff --git a/arch/tile/lib/spinlock_32.c b/arch/tile/lib/spinlock_32.c index 5cd1c4004eca..cb0999fb64b4 100644 --- a/arch/tile/lib/spinlock_32.c +++ b/arch/tile/lib/spinlock_32.c @@ -15,6 +15,7 @@ #include <linux/spinlock.h> #include <linux/module.h> #include <asm/processor.h> +#include <arch/spr_def.h> #include "spinlock_common.h" @@ -91,75 +92,75 @@ EXPORT_SYMBOL(arch_spin_unlock_wait); #define RD_COUNT_MASK ((1 << RD_COUNT_WIDTH) - 1) -/* Lock the word, spinning until there are no tns-ers. */ -static inline u32 get_rwlock(arch_rwlock_t *rwlock) -{ - u32 iterations = 0; - for (;;) { - u32 val = __insn_tns((int *)&rwlock->lock); - if (unlikely(val & 1)) { - delay_backoff(iterations++); - continue; - } - return val; - } -} - -int arch_read_trylock_slow(arch_rwlock_t *rwlock) -{ - u32 val = get_rwlock(rwlock); - int locked = (val << RD_COUNT_WIDTH) == 0; - rwlock->lock = val + (locked << RD_COUNT_SHIFT); - return locked; -} -EXPORT_SYMBOL(arch_read_trylock_slow); - -void arch_read_unlock_slow(arch_rwlock_t *rwlock) -{ - u32 val = get_rwlock(rwlock); - rwlock->lock = val - (1 << RD_COUNT_SHIFT); -} -EXPORT_SYMBOL(arch_read_unlock_slow); - -void arch_write_unlock_slow(arch_rwlock_t *rwlock, u32 val) +/* + * We can get the read lock if everything but the reader bits (which + * are in the high part of the word) is zero, i.e. no active or + * waiting writers, no tns. + * + * We guard the tns/store-back with an interrupt critical section to + * preserve the semantic that the same read lock can be acquired in an + * interrupt context. + */ +inline int arch_read_trylock(arch_rwlock_t *rwlock) { - u32 eq, mask = 1 << WR_CURR_SHIFT; - while (unlikely(val & 1)) { - /* Limited backoff since we are the highest-priority task. */ - relax(4); - val = __insn_tns((int *)&rwlock->lock); + u32 val; + __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 1); + val = __insn_tns((int *)&rwlock->lock); + if (likely((val << _RD_COUNT_WIDTH) == 0)) { + val += 1 << RD_COUNT_SHIFT; + rwlock->lock = val; + __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 0); + BUG_ON(val == 0); /* we don't expect wraparound */ + return 1; } - val = __insn_addb(val, mask); - eq = __insn_seqb(val, val << (WR_CURR_SHIFT - WR_NEXT_SHIFT)); - val = __insn_mz(eq & mask, val); - rwlock->lock = val; + if ((val & 1) == 0) + rwlock->lock = val; + __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 0); + return 0; } -EXPORT_SYMBOL(arch_write_unlock_slow); +EXPORT_SYMBOL(arch_read_trylock); /* - * We spin until everything but the reader bits (which are in the high - * part of the word) are zero, i.e. no active or waiting writers, no tns. - * + * Spin doing arch_read_trylock() until we acquire the lock. * ISSUE: This approach can permanently starve readers. A reader who sees * a writer could instead take a ticket lock (just like a writer would), * and atomically enter read mode (with 1 reader) when it gets the ticket. - * This way both readers and writers will always make forward progress + * This way both readers and writers would always make forward progress * in a finite time. */ -void arch_read_lock_slow(arch_rwlock_t *rwlock, u32 val) +void arch_read_lock(arch_rwlock_t *rwlock) { u32 iterations = 0; - do { - if (!(val & 1)) - rwlock->lock = val; + while (unlikely(!arch_read_trylock(rwlock))) delay_backoff(iterations++); +} +EXPORT_SYMBOL(arch_read_lock); + +void arch_read_unlock(arch_rwlock_t *rwlock) +{ + u32 val, iterations = 0; + + mb(); /* guarantee anything modified under the lock is visible */ + for (;;) { + __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 1); val = __insn_tns((int *)&rwlock->lock); - } while ((val << RD_COUNT_WIDTH) != 0); - rwlock->lock = val + (1 << RD_COUNT_SHIFT); + if (likely(val & 1) == 0) { + rwlock->lock = val - (1 << _RD_COUNT_SHIFT); + __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 0); + break; + } + __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 0); + delay_backoff(iterations++); + } } -EXPORT_SYMBOL(arch_read_lock_slow); +EXPORT_SYMBOL(arch_read_unlock); -void arch_write_lock_slow(arch_rwlock_t *rwlock, u32 val) +/* + * We don't need an interrupt critical section here (unlike for + * arch_read_lock) since we should never use a bare write lock where + * it could be interrupted by code that could try to re-acquire it. + */ +void arch_write_lock(arch_rwlock_t *rwlock) { /* * The trailing underscore on this variable (and curr_ below) @@ -168,6 +169,12 @@ void arch_write_lock_slow(arch_rwlock_t *rwlock, u32 val) */ u32 my_ticket_; u32 iterations = 0; + u32 val = __insn_tns((int *)&rwlock->lock); + + if (likely(val == 0)) { + rwlock->lock = 1 << _WR_NEXT_SHIFT; + return; + } /* * Wait until there are no readers, then bump up the next @@ -206,23 +213,47 @@ void arch_write_lock_slow(arch_rwlock_t *rwlock, u32 val) relax(4); } } -EXPORT_SYMBOL(arch_write_lock_slow); +EXPORT_SYMBOL(arch_write_lock); -int __tns_atomic_acquire(atomic_t *lock) +int arch_write_trylock(arch_rwlock_t *rwlock) { - int ret; - u32 iterations = 0; + u32 val = __insn_tns((int *)&rwlock->lock); - BUG_ON(__insn_mfspr(SPR_INTERRUPT_CRITICAL_SECTION)); - __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 1); + /* + * If a tns is in progress, or there's a waiting or active locker, + * or active readers, we can't take the lock, so give up. + */ + if (unlikely(val != 0)) { + if (!(val & 1)) + rwlock->lock = val; + return 0; + } - while ((ret = __insn_tns((void *)&lock->counter)) == 1) - delay_backoff(iterations++); - return ret; + /* Set the "next" field to mark it locked. */ + rwlock->lock = 1 << _WR_NEXT_SHIFT; + return 1; } +EXPORT_SYMBOL(arch_write_trylock); -void __tns_atomic_release(atomic_t *p, int v) +void arch_write_unlock(arch_rwlock_t *rwlock) { - p->counter = v; - __insn_mtspr(SPR_INTERRUPT_CRITICAL_SECTION, 0); + u32 val, eq, mask; + + mb(); /* guarantee anything modified under the lock is visible */ + val = __insn_tns((int *)&rwlock->lock); + if (likely(val == (1 << _WR_NEXT_SHIFT))) { + rwlock->lock = 0; + return; + } + while (unlikely(val & 1)) { + /* Limited backoff since we are the highest-priority task. */ + relax(4); + val = __insn_tns((int *)&rwlock->lock); + } + mask = 1 << WR_CURR_SHIFT; + val = __insn_addb(val, mask); + eq = __insn_seqb(val, val << (WR_CURR_SHIFT - WR_NEXT_SHIFT)); + val = __insn_mz(eq & mask, val); + rwlock->lock = val; } +EXPORT_SYMBOL(arch_write_unlock); |