1 files changed, 22 insertions, 0 deletions
diff --git a/src/stdio/putc.h b/src/stdio/putc.h
new file mode 100644
index 00000000..2014c4ec
--- /dev/null
+++ b/src/stdio/putc.h
@@ -0,0 +1,22 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+#ifdef __GNUC__
+__attribute__((__noinline__))
+#endif
+static int locking_putc(int c, FILE *f)
+{
+	if (a_cas(&f->lock, 0, MAYBE_WAITERS-1)) __lockfile(f);
+	c = putc_unlocked(c, f);
+	if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
+		__wake(&f->lock, 1, 1);
+	return c;
+}
+
+static inline int do_putc(int c, FILE *f)
+{
+	int l = f->lock;
+	if (l < 0 || l && (l & ~MAYBE_WAITERS) == __pthread_self()->tid)
+		return putc_unlocked(c, f);
+	return locking_putc(c, f);
+}