#include "stdio_impl.h"
#include "pthread_impl.h"
-void __lockfile(FILE *f)
-{
- int spins=100000;
- int tid;
+#define MAYBE_WAITERS 0x40000000
- if (f->lock < 0) return;
- tid = __pthread_self()->tid;
- if (f->lock == tid) {
- while (f->lockcount == INT_MAX);
- f->lockcount++;
- return;
+int __lockfile(FILE *f)
+{
+ int owner = f->lock, tid = __pthread_self()->tid;
+ if ((owner & ~MAYBE_WAITERS) == tid)
+ return 0;
+ for (;;) {
+ owner = a_cas(&f->lock, 0, tid);
+ if (!owner) return 1;
+ if (a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner) break;
}
- while (a_cas(&f->lock, 0, tid))
- if (spins) spins--, a_spin();
- else syscall(SYS_sched_yield);
- f->lockcount = 1;
+ while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS)))
+ __futexwait(&f->lock, owner, 1);
+ return 1;
+}
+
+void __unlockfile(FILE *f)
+{
+ if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
+ __wake(&f->lock, 1, 1);
}