source: asp3_tinet_ecnl_arm/trunk/musl-1.1.18/src/stdio/__lockfile.c@ 352

#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);
}