[4.1] c6efe04 Add error checking to confirm bug

[PÃ¥l Hermunn Johansen]

commit c6efe045ff12c1f192d15caf5683f65b0aca34e2
Author: Pål Hermunn Johansen <hermunn at varnish-software.com>
Date:   Wed Sep 28 14:54:29 2016 +0200

    Add error checking to confirm bug
    
    There seems to be an error in the varnish jail design, which makes the
    mgt process uable to kill the child process. To confirm this, add some
    error checking to the relevant code.
    
    Related to: #2010

diff --git a/bin/varnishd/mgt/mgt_child.c b/bin/varnishd/mgt/mgt_child.c
index 2fa0795..f89f6d4 100644
--- a/bin/varnishd/mgt/mgt_child.c
+++ b/bin/varnishd/mgt/mgt_child.c
@@ -34,6 +34,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
+#include <errno.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <signal.h>
@@ -587,17 +588,22 @@ mgt_reap_child(void)
 void
 MGT_Child_Cli_Fail(void)
 {
+	int i;
 
 	if (child_state != CH_RUNNING)
 		return;
 	if (child_pid < 0)
 		return;
-	MGT_complain(C_ERR, "Child (%jd) not responding to CLI, killing it.",
-	    (intmax_t)child_pid);
 	if (MGT_FEATURE(FEATURE_NO_COREDUMP))
-		(void)kill(child_pid, SIGKILL);
+		i = kill(child_pid, SIGKILL);
+	else
+		i = kill(child_pid, SIGQUIT);
+	if (i == 0)
+		MGT_complain(C_ERR, "Child (%jd) not responding to CLI,"
+		    " killing it.", (intmax_t)child_pid);
 	else
-		(void)kill(child_pid, SIGQUIT);
+		MGT_complain(C_ERR, "Failed to kill child with PID %jd: %s",
+		    (intmax_t)child_pid, strerror(errno));
 }
 
 /*=====================================================================