1#include "stdio_impl.h"
2#include "pthread_impl.h"
3
4int __lockfile(FILE *f)
5{
6	int owner, tid = __pthread_self()->tid;
7	if (f->lock == tid)
8		return 0;
9	while ((owner = a_cas(&f->lock, 0, tid)))
10		__wait(&f->lock, &f->waiters, owner, 1);
11	return 1;
12}
13
14void __unlockfile(FILE *f)
15{
16	a_store(&f->lock, 0);
17
18	/* The following read is technically invalid under situations
19	 * of self-synchronized destruction. Another thread may have
20	 * called fclose as soon as the above store has completed.
21	 * Nonetheless, since FILE objects always live in memory
22	 * obtained by malloc from the heap, it's safe to assume
23	 * the dereferences below will not fault. In the worst case,
24	 * a spurious syscall will be made. If the implementation of
25	 * malloc changes, this assumption needs revisiting. */
26
27	if (f->waiters) __wake(&f->lock, 1, 1);
28}
29