net: select with deadlines (#14369)

Author: emily33901

vlib/net/common.v

@@ -65,56 +65,51 @@ fn @select(handle int, test Select, timeout time.Duration) ?bool {
 	return C.FD_ISSET(handle, &set)
 }
 
-// select_with_retry will retry the select if select is failing
-// due to interrupted system call. This can happen on signals
-// for example the GC Boehm uses signals internally on garbage
-// collection
 [inline]
-fn select_with_retry(handle int, test Select, timeout time.Duration) ?bool {
-	mut retries := 10
-	for retries > 0 {
+fn select_deadline(handle int, test Select, deadline time.Time) ?bool {
+	// if we have a 0 deadline here then the timeout that was passed was infinite...
+	infinite := deadline.unix_time() == 0
+	for infinite || time.now() <= deadline {
+		timeout := if infinite { net.infinite_timeout } else { deadline - time.now() }
 		ready := @select(handle, test, timeout) or {
 			if err.code() == 4 {
-				// signal! lets retry max 10 times
-				// suspend thread with sleep to let the gc get
-				// cycles in the case the Bohem gc is interupting
-				time.sleep(1 * time.millisecond)
-				retries -= 1
+				// Spurious wakeup from signal, keep waiting
 				continue
 			}
-			// we got other error
+
+			// NOT a spurious wakeup
 			return err
 		}
+
 		return ready
 	}
-	return error('failed to @select more that three times due to interrupted system call')
+
+	// Deadline elapsed
+	return false
 }
 
 // wait_for_common wraps the common wait code
 fn wait_for_common(handle int, deadline time.Time, timeout time.Duration, test Select) ? {
-	if deadline.unix == 0 {
-		// do not accept negative timeout
-		if timeout < 0 {
-			return err_timed_out
-		}
-		ready := select_with_retry(handle, test, timeout) ?
-		if ready {
-			return
-		}
-		return err_timed_out
+	// Convert timeouts to deadlines
+	real_deadline := if timeout == net.infinite_timeout {
+		time.unix(0)
+	} else if timeout == 0 {
+		// No timeout set, so assume deadline
+		deadline
+	} else if timeout < 0 {
+		// TODO(emily): Do something nicer here :)
+		panic('invalid negative timeout')
+	} else {
+		// timeout
+		time.now().add(timeout)
 	}
-	// Convert the deadline into a timeout
-	// and use that
-	d_timeout := deadline.unix - time.now().unix
-	if d_timeout < 0 {
-		// deadline is in the past so this has already
-		// timed out
-		return err_timed_out
-	}
-	ready := select_with_retry(handle, test, timeout) ?
+
+	ready := select_deadline(handle, test, real_deadline) ?
+
 	if ready {
 		return
 	}
+
 	return err_timed_out
 }