forked from luck/tmp_suning_uos_patched
8e34703b93
Matthew Wilcox pointed out that the generic implementation of this is unfit for use. Here's an ARM optimised version instead. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
222 lines
4.2 KiB
C
222 lines
4.2 KiB
C
#ifndef __ASM_SPINLOCK_H
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#define __ASM_SPINLOCK_H
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#if __LINUX_ARM_ARCH__ < 6
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#error SMP not supported on pre-ARMv6 CPUs
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#endif
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/*
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* ARMv6 Spin-locking.
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*
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* We exclusively read the old value. If it is zero, we may have
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* won the lock, so we try exclusively storing it. A memory barrier
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* is required after we get a lock, and before we release it, because
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* V6 CPUs are assumed to have weakly ordered memory.
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*
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* Unlocked value: 0
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* Locked value: 1
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*/
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#define __raw_spin_is_locked(x) ((x)->lock != 0)
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#define __raw_spin_unlock_wait(lock) \
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do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
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#define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
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static inline void __raw_spin_lock(raw_spinlock_t *lock)
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{
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unsigned long tmp;
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__asm__ __volatile__(
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"1: ldrex %0, [%1]\n"
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" teq %0, #0\n"
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#ifdef CONFIG_CPU_32v6K
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" wfene\n"
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#endif
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" strexeq %0, %2, [%1]\n"
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" teqeq %0, #0\n"
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" bne 1b"
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: "=&r" (tmp)
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: "r" (&lock->lock), "r" (1)
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: "cc");
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smp_mb();
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}
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static inline int __raw_spin_trylock(raw_spinlock_t *lock)
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{
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unsigned long tmp;
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__asm__ __volatile__(
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" ldrex %0, [%1]\n"
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" teq %0, #0\n"
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" strexeq %0, %2, [%1]"
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: "=&r" (tmp)
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: "r" (&lock->lock), "r" (1)
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: "cc");
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if (tmp == 0) {
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smp_mb();
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return 1;
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} else {
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return 0;
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}
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}
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static inline void __raw_spin_unlock(raw_spinlock_t *lock)
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{
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smp_mb();
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__asm__ __volatile__(
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" str %1, [%0]\n"
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#ifdef CONFIG_CPU_32v6K
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" mcr p15, 0, %1, c7, c10, 4\n" /* DSB */
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" sev"
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#endif
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:
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: "r" (&lock->lock), "r" (0)
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: "cc");
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}
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/*
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* RWLOCKS
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*
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*
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* Write locks are easy - we just set bit 31. When unlocking, we can
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* just write zero since the lock is exclusively held.
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*/
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#define rwlock_is_locked(x) (*((volatile unsigned int *)(x)) != 0)
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static inline void __raw_write_lock(raw_rwlock_t *rw)
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{
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unsigned long tmp;
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__asm__ __volatile__(
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"1: ldrex %0, [%1]\n"
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" teq %0, #0\n"
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#ifdef CONFIG_CPU_32v6K
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" wfene\n"
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#endif
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" strexeq %0, %2, [%1]\n"
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" teq %0, #0\n"
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" bne 1b"
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: "=&r" (tmp)
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: "r" (&rw->lock), "r" (0x80000000)
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: "cc");
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smp_mb();
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}
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static inline int __raw_write_trylock(raw_rwlock_t *rw)
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{
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unsigned long tmp;
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__asm__ __volatile__(
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"1: ldrex %0, [%1]\n"
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" teq %0, #0\n"
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" strexeq %0, %2, [%1]"
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: "=&r" (tmp)
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: "r" (&rw->lock), "r" (0x80000000)
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: "cc");
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if (tmp == 0) {
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smp_mb();
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return 1;
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} else {
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return 0;
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}
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}
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static inline void __raw_write_unlock(raw_rwlock_t *rw)
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{
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smp_mb();
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__asm__ __volatile__(
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"str %1, [%0]\n"
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#ifdef CONFIG_CPU_32v6K
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" mcr p15, 0, %1, c7, c10, 4\n" /* DSB */
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" sev\n"
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#endif
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:
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: "r" (&rw->lock), "r" (0)
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: "cc");
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}
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/* write_can_lock - would write_trylock() succeed? */
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#define __raw_write_can_lock(x) ((x)->lock == 0x80000000)
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/*
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* Read locks are a bit more hairy:
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* - Exclusively load the lock value.
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* - Increment it.
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* - Store new lock value if positive, and we still own this location.
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* If the value is negative, we've already failed.
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* - If we failed to store the value, we want a negative result.
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* - If we failed, try again.
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* Unlocking is similarly hairy. We may have multiple read locks
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* currently active. However, we know we won't have any write
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* locks.
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*/
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static inline void __raw_read_lock(raw_rwlock_t *rw)
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{
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unsigned long tmp, tmp2;
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__asm__ __volatile__(
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"1: ldrex %0, [%2]\n"
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" adds %0, %0, #1\n"
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" strexpl %1, %0, [%2]\n"
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#ifdef CONFIG_CPU_32v6K
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" wfemi\n"
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#endif
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" rsbpls %0, %1, #0\n"
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" bmi 1b"
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: "=&r" (tmp), "=&r" (tmp2)
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: "r" (&rw->lock)
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: "cc");
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smp_mb();
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}
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static inline void __raw_read_unlock(raw_rwlock_t *rw)
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{
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unsigned long tmp, tmp2;
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smp_mb();
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__asm__ __volatile__(
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"1: ldrex %0, [%2]\n"
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" sub %0, %0, #1\n"
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" strex %1, %0, [%2]\n"
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" teq %1, #0\n"
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" bne 1b"
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#ifdef CONFIG_CPU_32v6K
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"\n cmp %0, #0\n"
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" mcreq p15, 0, %0, c7, c10, 4\n"
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" seveq"
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#endif
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: "=&r" (tmp), "=&r" (tmp2)
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: "r" (&rw->lock)
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: "cc");
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}
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static inline int __raw_read_trylock(raw_rwlock_t *rw)
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{
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unsigned long tmp tmp2 = 1;
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__asm__ __volatile__(
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"1: ldrex %0, [%2]\n"
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" adds %0, %0, #1\n"
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" strexpl %1, %0, [%2]\n"
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: "=&r" (tmp), "+r" (tmp2)
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: "r" (&rw->lock)
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: "cc");
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smp_mb();
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return tmp2 == 0;
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}
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/* read_can_lock - would read_trylock() succeed? */
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#define __raw_read_can_lock(x) ((x)->lock < 0x80000000)
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#endif /* __ASM_SPINLOCK_H */
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