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