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| | #include "stdio_impl.h"
#include "pthread_impl.h"
#define MAYBE_WAITERS 0x40000000
int __lockfile(FILE *f)
{
int owner = f->lock, tid = __pthread_self()->tid;
if ((owner & ~MAYBE_WAITERS) == tid)
return 0;
owner = a_cas(&f->lock, 0, tid);
if (!owner) return 1;
while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) {
if ((owner & MAYBE_WAITERS) ||
a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner)
__futexwait(&f->lock, owner|MAYBE_WAITERS, 1);
}
return 1;
}
void __unlockfile(FILE *f)
{
if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
__wake(&f->lock, 1, 1);
}
|