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optimize contended normal mutex case; add int compare-and-swap atomic

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This commit is contained in:
Rich Felker 2011-03-17 12:14:40 -04:00
parent 1d59f1eddb
commit e914f8b7ec
3 changed files with 15 additions and 1 deletions
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7
arch/i386/atomic.h
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@ -49,6 +49,13 @@ static inline long a_cas_l(volatile void *p, long t, long s)
return t;
}
static inline int a_cas(volatile int *p, int t, int s)
{
__asm__( "lock ; cmpxchg %3, %1"
: "=a"(t), "=m"(*p) : "a"(t), "r"(s) : "memory" );
return t;
}
static inline void *a_swap_p(void *volatile *x, void *v)
{
__asm__( "xchg %0, %1" : "=r"(v), "=m"(*(void **)x) : "0"(v) : "memory" );

7
arch/x86_64/atomic.h
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@ -48,6 +48,13 @@ static inline long a_cas_l(volatile void *p, long t, long s)
return t;
}
static inline int a_cas(volatile int *p, int t, int s)
{
__asm__( "lock ; cmpxchgl %3, %1"
: "=a"(t), "=m"(*p) : "a"(t), "r"(s) : "memory" );
return t;
}
static inline void *a_swap_p(void *volatile *x, void *v)
{
__asm__( "xchg %0, %1" : "=r"(v), "=m"(*(void **)x) : "0"(v) : "memory" );

2
src/thread/pthread_mutex_trylock.c
View File

@ -5,7 +5,7 @@ int pthread_mutex_trylock(pthread_mutex_t *m)
int tid;
if (m->_m_type == PTHREAD_MUTEX_NORMAL)
return -a_xchg(&m->_m_lock, 1) & EBUSY;
return (m->_m_lock || a_swap(&m->_m_lock, 1)) ? EBUSY : 0;
tid = pthread_self()->tid;