hush: rename last_waitpid_was_0 to we_have_children

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 19 insertions, 11 deletions

diff --git a/shell/hush.c b/shell/hush.c
index fd839d061..7360f0e4c 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -495,7 +495,7 @@ struct globals {
 #if ENABLE_HUSH_FAST
 	unsigned count_SIGCHLD;
 	unsigned handled_SIGCHLD;
-	smallint last_waitpid_was_0;
+	smallint we_have_children;
 #endif
 	/* which signals have non-DFL handler (even with no traps set)? */
 	unsigned non_DFL_mask;
@@ -3292,22 +3292,30 @@ static int checkjobs(struct pipe* fg_pipe)
 
 	debug_printf_jobs("checkjobs %p\n", fg_pipe);
 
+	attributes = WUNTRACED;
+	if (fg_pipe == NULL)
+		attributes |= WNOHANG;
+
 	errno = 0;
 #if ENABLE_HUSH_FAST
 	if (G.handled_SIGCHLD == G.count_SIGCHLD) {
-//bb_error_msg("[%d] checkjobs: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d was 0?:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD, G.last_waitpid_was_0);
-		/* avoid doing syscall, nothing there anyway */
-		if (G.last_waitpid_was_0)
+//bb_error_msg("[%d] checkjobs: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d children?:%d fg_pipe:%p",
+//getpid(), G.count_SIGCHLD, G.handled_SIGCHLD, G.we_have_children, fg_pipe);
+		/* There was heither fork nor SIGCHLD since last waitpid */
+		/* Avoid doing syscall, nothing there anyway */
+		if (!G.we_have_children) {
+			errno = ECHILD;
+			return -1;
+		}
+		if (fg_pipe == NULL) { /* is WNOHANG set? */
+			/* We have children, but they did not exit
+			 * or stop yet (we saw no SIGCHLD) */
 			return 0;
-		errno = ECHILD;
-		return -1;
+		}
+		/* else: !WNOHANG, waitpid will block, can't short-circuit */
 	}
 #endif
 
-	attributes = WUNTRACED;
-	if (fg_pipe == NULL)
-		attributes |= WNOHANG;
-
 /* Do we do this right?
  * bash-3.00# sleep 20 | false
  * <ctrl-Z pressed>
@@ -3330,7 +3338,7 @@ static int checkjobs(struct pipe* fg_pipe)
 				bb_perror_msg("waitpid");
 #if ENABLE_HUSH_FAST
 			else { /* Until next SIGCHLD, waitpid's are useless */
-				G.last_waitpid_was_0 = (childpid == 0);
+				G.we_have_children = (childpid == 0);
 				G.handled_SIGCHLD = i;
 //bb_error_msg("[%d] checkjobs: waitpid returned <= 0, G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
 			}