implement flockfile api, rework stdio locking

src/stdio/__lockfile.c

@@ -0,0 +1,19 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void __lockfile(FILE *f)
+{
+	int spins;
+	if (f->owner < 0) return;
+	if (f->owner && f->owner == __pthread_self()->tid) {
+		while (f->lockcount == INT_MAX);
+		f->lockcount++;
+		return;
+	}
+	spins = 100000;
+	while (a_swap(&f->lock, 1))
+		if (spins) spins--, a_spin();
+		else syscall0(__NR_sched_yield);
+	f->owner = __pthread_self()->tid;
+	f->lockcount = 1;
+}

src/stdio/__ofl.c

@@ -1,3 +0,0 @@
-#include "stdio_impl.h"
-
-struct ofl __ofl;

src/stdio/flockfile.c

@@ -0,0 +1,9 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void flockfile(FILE *f)
+{
+	pthread_self();
+	libc.lockfile = __lockfile;
+	__lockfile(f);
+}

src/stdio/ftrylockfile.c

@@ -0,0 +1,18 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+int ftrylockfile(FILE *f)
+{
+	libc.lockfile = __lockfile;
+	if (f->owner && f->owner == pthread_self()->tid) {
+		if (f->lockcount == INT_MAX)
+			return -1;
+		f->lockcount++;
+		return 0;
+	}
+	if (a_swap(&f->lock, 1))
+		return -1;
+	f->owner = pthread_self()->tid;
+	f->lockcount = 1;
+	return 0;
+}

src/stdio/funlockfile.c

@@ -0,0 +1,7 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+void funlockfile(FILE *f)
+{
+	FUNLOCK(f);
+}

src/stdio/vsnprintf.c

@@ -17,6 +17,7 @@ int vsnprintf(char *s, size_t n, const char *fmt, va_list ap)
 	f.write = sn_write;
 	f.buf_size = 1;
 	f.buf = buf;
+	f.owner = -1;
 	if (n > INT_MAX) {
 		errno = EOVERFLOW;
 		return -1;