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#include "stdio_impl.h"
#include "pthread_impl.h"
int __lockfile(FILE *f)
{
int owner, tid = __pthread_self()->tid;
if (f->lock == tid)
return 0;
while ((owner = a_cas(&f->lock, 0, tid)))
__wait(&f->lock, &f->waiters, owner, 1);
return 1;
}
void __unlockfile(FILE *f)
{
a_store(&f->lock, 0);
/* The following read is technically invalid under situations
* of self-synchronized destruction. Another thread may have
* called fclose as soon as the above store has completed.
* Nonetheless, since FILE objects always live in memory
* obtained by malloc from the heap, it's safe to assume
* the dereferences below will not fault. In the worst case,
* a spurious syscall will be made. If the implementation of
* malloc changes, this assumption needs revisiting. */
if (f->waiters) __wake(&f->lock, 1, 1);
}
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