a

libc/time.c

@@ -0,0 +1,51 @@
+#include <u.h>
+#include <libc.h>
+
+
+/*
+ *  After a fork with fd's copied, both fd's are pointing to
+ *  the same Chan structure.  Since the offset is kept in the Chan
+ *  structure, the seek's and read's in the two processes can
+ *  compete at moving the offset around.  Hence the unusual loop
+ *  in the middle of this routine.
+ */
+static long
+oldtime(long *tp)
+{
+	char b[20];
+	static int f = -1;
+	int i, retries;
+	long t;
+
+	memset(b, 0, sizeof(b));
+	for(retries = 0; retries < 100; retries++){
+		if(f < 0)
+			f = open("/dev/time", OREAD|OCEXEC);
+		if(f < 0)
+			break;
+		if(seek(f, 0, 0) < 0 || (i = read(f, b, sizeof(b))) < 0){
+			close(f);
+			f = -1;
+		} else {
+			if(i != 0)
+				break;
+		}
+	}
+	t = atol(b);
+	if(tp)
+		*tp = t;
+	return t;
+}
+
+long
+time(long *tp)
+{
+	vlong t;
+
+	t = nsec()/((vlong)1000000000);
+	if(t == 0)
+		t = oldtime(0);
+	if(tp != nil)
+		*tp = t;
+	return t;
+}