36180: avoid infinite job stop/continue loop on "wait PID" for a background job

2 files changed, 13 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index a13e05d08..2966957fb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-08-15  Barton E. Schaefer  <schaefer@zsh.org>
+
+	* 36180: Src/jobs.c: avoid infinite job stop/continue loop on
+	"wait PID" for a background job
+
 2015-08-15  Mikael Magnusson  <mikachu@gmail.com>
 
 	* Eric Cook: 36091: Completion/Unix/Command/_ncftp: search
diff --git a/Src/jobs.c b/Src/jobs.c
index ed647b87e..b47ba8c60 100644
--- a/Src/jobs.c
+++ b/Src/jobs.c
@@ -1384,10 +1384,17 @@ waitforpid(pid_t pid, int wait_cmd)
     dont_queue_signals();
     child_block();		/* unblocked in signal_suspend() */
     queue_traps(wait_cmd);
+
+    /* This function should never be called with a pid that is not a
+     * child of the current shell.  Consequently, if kill(0, pid)
+     * fails here with ESRCH, the child has already been reaped.  In
+     * the loop body, we expect this to happen in signal_suspend()
+     * via zhandler(), after which this test terminates the loop.
+     */
     while (!errflag && (kill(pid, 0) >= 0 || errno != ESRCH)) {
 	if (first)
 	    first = 0;
-	else
+	else if (!wait_cmd)
 	    kill(pid, SIGCONT);
 
 	last_signal = -1;