diff options
Diffstat (limited to 'arch/arm/include/asm/spinlock.h')
| -rw-r--r-- | arch/arm/include/asm/spinlock.h | 149 |
1 files changed, 72 insertions, 77 deletions
diff --git a/arch/arm/include/asm/spinlock.h b/arch/arm/include/asm/spinlock.h index b4ca707d0a6..ac4bfae2670 100644 --- a/arch/arm/include/asm/spinlock.h +++ b/arch/arm/include/asm/spinlock.h @@ -5,21 +5,13 @@ #error SMP not supported on pre-ARMv6 CPUs #endif -#include <asm/processor.h> +#include <linux/prefetch.h> /* * sev and wfe are ARMv6K extensions. Uniprocessor ARMv6 may not have the K * extensions, so when running on UP, we have to patch these instructions away. */ -#define ALT_SMP(smp, up) \ - "9998: " smp "\n" \ - " .pushsection \".alt.smp.init\", \"a\"\n" \ - " .long 9998b\n" \ - " " up "\n" \ - " .popsection\n" - #ifdef CONFIG_THUMB2_KERNEL -#define SEV ALT_SMP("sev.w", "nop.w") /* * For Thumb-2, special care is needed to ensure that the conditional WFE * instruction really does assemble to exactly 4 bytes (as required by @@ -31,31 +23,23 @@ * the assembler won't change IT instructions which are explicitly present * in the input. */ -#define WFE(cond) ALT_SMP( \ +#define WFE(cond) __ALT_SMP_ASM( \ "it " cond "\n\t" \ "wfe" cond ".n", \ \ "nop.w" \ ) #else -#define SEV ALT_SMP("sev", "nop") -#define WFE(cond) ALT_SMP("wfe" cond, "nop") +#define WFE(cond) __ALT_SMP_ASM("wfe" cond, "nop") #endif +#define SEV __ALT_SMP_ASM(WASM(sev), WASM(nop)) + static inline void dsb_sev(void) { -#if __LINUX_ARM_ARCH__ >= 7 - __asm__ __volatile__ ( - "dsb\n" - SEV - ); -#else - __asm__ __volatile__ ( - "mcr p15, 0, %0, c7, c10, 4\n" - SEV - : : "r" (0) - ); -#endif + + dsb(ishst); + __asm__(SEV); } /* @@ -77,6 +61,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) u32 newval; arch_spinlock_t lockval; + prefetchw(&lock->slock); __asm__ __volatile__( "1: ldrex %0, [%3]\n" " add %1, %0, %4\n" @@ -97,19 +82,23 @@ static inline void arch_spin_lock(arch_spinlock_t *lock) static inline int arch_spin_trylock(arch_spinlock_t *lock) { - unsigned long tmp; + unsigned long contended, res; u32 slock; - __asm__ __volatile__( -" ldrex %0, [%2]\n" -" subs %1, %0, %0, ror #16\n" -" addeq %0, %0, %3\n" -" strexeq %1, %0, [%2]" - : "=&r" (slock), "=&r" (tmp) - : "r" (&lock->slock), "I" (1 << TICKET_SHIFT) - : "cc"); - - if (tmp == 0) { + prefetchw(&lock->slock); + do { + __asm__ __volatile__( + " ldrex %0, [%3]\n" + " mov %2, #0\n" + " subs %1, %0, %0, ror #16\n" + " addeq %0, %0, %4\n" + " strexeq %2, %0, [%3]" + : "=&r" (slock), "=&r" (contended), "=&r" (res) + : "r" (&lock->slock), "I" (1 << TICKET_SHIFT) + : "cc"); + } while (res); + + if (!contended) { smp_mb(); return 1; } else { @@ -119,29 +108,19 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock) static inline void arch_spin_unlock(arch_spinlock_t *lock) { - unsigned long tmp; - u32 slock; - smp_mb(); - - __asm__ __volatile__( -" mov %1, #1\n" -"1: ldrex %0, [%2]\n" -" uadd16 %0, %0, %1\n" -" strex %1, %0, [%2]\n" -" teq %1, #0\n" -" bne 1b" - : "=&r" (slock), "=&r" (tmp) - : "r" (&lock->slock) - : "cc"); - + lock->tickets.owner++; dsb_sev(); } +static inline int arch_spin_value_unlocked(arch_spinlock_t lock) +{ + return lock.tickets.owner == lock.tickets.next; +} + static inline int arch_spin_is_locked(arch_spinlock_t *lock) { - struct __raw_tickets tickets = ACCESS_ONCE(lock->tickets); - return tickets.owner != tickets.next; + return !arch_spin_value_unlocked(ACCESS_ONCE(*lock)); } static inline int arch_spin_is_contended(arch_spinlock_t *lock) @@ -163,6 +142,7 @@ static inline void arch_write_lock(arch_rwlock_t *rw) { unsigned long tmp; + prefetchw(&rw->lock); __asm__ __volatile__( "1: ldrex %0, [%1]\n" " teq %0, #0\n" @@ -179,17 +159,21 @@ static inline void arch_write_lock(arch_rwlock_t *rw) static inline int arch_write_trylock(arch_rwlock_t *rw) { - unsigned long tmp; - - __asm__ __volatile__( -" ldrex %0, [%1]\n" -" teq %0, #0\n" -" strexeq %0, %2, [%1]" - : "=&r" (tmp) - : "r" (&rw->lock), "r" (0x80000000) - : "cc"); - - if (tmp == 0) { + unsigned long contended, res; + + prefetchw(&rw->lock); + do { + __asm__ __volatile__( + " ldrex %0, [%2]\n" + " mov %1, #0\n" + " teq %0, #0\n" + " strexeq %1, %3, [%2]" + : "=&r" (contended), "=&r" (res) + : "r" (&rw->lock), "r" (0x80000000) + : "cc"); + } while (res); + + if (!contended) { smp_mb(); return 1; } else { @@ -211,7 +195,7 @@ static inline void arch_write_unlock(arch_rwlock_t *rw) } /* write_can_lock - would write_trylock() succeed? */ -#define arch_write_can_lock(x) ((x)->lock == 0) +#define arch_write_can_lock(x) (ACCESS_ONCE((x)->lock) == 0) /* * Read locks are a bit more hairy: @@ -229,6 +213,7 @@ static inline void arch_read_lock(arch_rwlock_t *rw) { unsigned long tmp, tmp2; + prefetchw(&rw->lock); __asm__ __volatile__( "1: ldrex %0, [%2]\n" " adds %0, %0, #1\n" @@ -249,6 +234,7 @@ static inline void arch_read_unlock(arch_rwlock_t *rw) smp_mb(); + prefetchw(&rw->lock); __asm__ __volatile__( "1: ldrex %0, [%2]\n" " sub %0, %0, #1\n" @@ -265,22 +251,31 @@ static inline void arch_read_unlock(arch_rwlock_t *rw) static inline int arch_read_trylock(arch_rwlock_t *rw) { - unsigned long tmp, tmp2 = 1; - - __asm__ __volatile__( -" ldrex %0, [%2]\n" -" adds %0, %0, #1\n" -" strexpl %1, %0, [%2]\n" - : "=&r" (tmp), "+r" (tmp2) - : "r" (&rw->lock) - : "cc"); - - smp_mb(); - return tmp2 == 0; + unsigned long contended, res; + + prefetchw(&rw->lock); + do { + __asm__ __volatile__( + " ldrex %0, [%2]\n" + " mov %1, #0\n" + " adds %0, %0, #1\n" + " strexpl %1, %0, [%2]" + : "=&r" (contended), "=&r" (res) + : "r" (&rw->lock) + : "cc"); + } while (res); + + /* If the lock is negative, then it is already held for write. */ + if (contended < 0x80000000) { + smp_mb(); + return 1; + } else { + return 0; + } } /* read_can_lock - would read_trylock() succeed? */ -#define arch_read_can_lock(x) ((x)->lock < 0x80000000) +#define arch_read_can_lock(x) (ACCESS_ONCE((x)->lock) < 0x80000000) #define arch_read_lock_flags(lock, flags) arch_read_lock(lock) #define arch_write_lock_flags(lock, flags) arch_write_lock(lock) |