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f10e2e5b4b
For performance reasons we are about to change ISYNC_ON_SMP to sometimes be lwsync. Now that the macro name doesn't make sense, change it and LWSYNC_ON_SMP to better explain what the barriers are doing. Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
135 lines
3.2 KiB
C
135 lines
3.2 KiB
C
/*
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* Optimised mutex implementation of include/asm-generic/mutex-dec.h algorithm
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*/
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#ifndef _ASM_POWERPC_MUTEX_H
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#define _ASM_POWERPC_MUTEX_H
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static inline int __mutex_cmpxchg_lock(atomic_t *v, int old, int new)
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{
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int t;
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__asm__ __volatile__ (
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"1: lwarx %0,0,%1 # mutex trylock\n\
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cmpw 0,%0,%2\n\
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bne- 2f\n"
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PPC405_ERR77(0,%1)
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" stwcx. %3,0,%1\n\
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bne- 1b"
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PPC_ACQUIRE_BARRIER
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"\n\
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2:"
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: "=&r" (t)
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: "r" (&v->counter), "r" (old), "r" (new)
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: "cc", "memory");
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return t;
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}
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static inline int __mutex_dec_return_lock(atomic_t *v)
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{
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int t;
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__asm__ __volatile__(
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"1: lwarx %0,0,%1 # mutex lock\n\
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addic %0,%0,-1\n"
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PPC405_ERR77(0,%1)
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" stwcx. %0,0,%1\n\
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bne- 1b"
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PPC_ACQUIRE_BARRIER
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: "=&r" (t)
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: "r" (&v->counter)
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: "cc", "memory");
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return t;
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}
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static inline int __mutex_inc_return_unlock(atomic_t *v)
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{
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int t;
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__asm__ __volatile__(
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PPC_RELEASE_BARRIER
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"1: lwarx %0,0,%1 # mutex unlock\n\
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addic %0,%0,1\n"
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PPC405_ERR77(0,%1)
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" stwcx. %0,0,%1 \n\
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bne- 1b"
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: "=&r" (t)
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: "r" (&v->counter)
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: "cc", "memory");
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return t;
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}
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/**
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* __mutex_fastpath_lock - try to take the lock by moving the count
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* from 1 to a 0 value
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* @count: pointer of type atomic_t
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* @fail_fn: function to call if the original value was not 1
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*
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* Change the count from 1 to a value lower than 1, and call <fail_fn> if
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* it wasn't 1 originally. This function MUST leave the value lower than
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* 1 even when the "1" assertion wasn't true.
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*/
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static inline void
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__mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *))
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{
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if (unlikely(__mutex_dec_return_lock(count) < 0))
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fail_fn(count);
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}
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/**
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* __mutex_fastpath_lock_retval - try to take the lock by moving the count
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* from 1 to a 0 value
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* @count: pointer of type atomic_t
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* @fail_fn: function to call if the original value was not 1
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*
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* Change the count from 1 to a value lower than 1, and call <fail_fn> if
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* it wasn't 1 originally. This function returns 0 if the fastpath succeeds,
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* or anything the slow path function returns.
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*/
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static inline int
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__mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *))
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{
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if (unlikely(__mutex_dec_return_lock(count) < 0))
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return fail_fn(count);
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return 0;
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}
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/**
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* __mutex_fastpath_unlock - try to promote the count from 0 to 1
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* @count: pointer of type atomic_t
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* @fail_fn: function to call if the original value was not 0
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*
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* Try to promote the count from 0 to 1. If it wasn't 0, call <fail_fn>.
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* In the failure case, this function is allowed to either set the value to
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* 1, or to set it to a value lower than 1.
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*/
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static inline void
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__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
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{
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if (unlikely(__mutex_inc_return_unlock(count) <= 0))
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fail_fn(count);
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}
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#define __mutex_slowpath_needs_to_unlock() 1
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/**
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* __mutex_fastpath_trylock - try to acquire the mutex, without waiting
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*
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* @count: pointer of type atomic_t
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* @fail_fn: fallback function
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*
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* Change the count from 1 to 0, and return 1 (success), or if the count
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* was not 1, then return 0 (failure).
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*/
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static inline int
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__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
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{
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if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
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return 1;
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return 0;
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}
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#endif
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