gdb.threads/thread-execl, don't re-exec forever

I noticed on Cygwin, gdb.thread/thread-execl.exp would hang, (not that
surprising since we can't follow-exec on Cygwin).  Looking at the
process list running on the machine, we end up with a thread-execl.exe
process constantly respawning another process [1].

We see the same constant-reexec if we launch gdb.thread/thread-execl
manually on the shell:

 $ ./testsuite/outputs/gdb.threads/thread-execl/thread-execl
 # * doesn't exit, constantly re-execing *
 ^C

Prevent this leftover constantly-re-execing scenario by making the
testcase program only exec once.  We now get:

  $ ./testsuite/outputs/gdb.threads/thread-execl/thread-execl
  $   # exits immediately after one exec.

On Cygwin, the testcase now fails reasonably quickly, and doesn't
leave stale processes behind.

Still passes cleanly on x86-64 GNU/Linux.

[1] Cygwin's exec emulation spawns a new Windows process for the new
image.

Approved-By: Andrew Burgess <aburgess@redhat.com>
Change-Id: I0de1136cf2ef7e89465189bc43489a2139a80efb

diff --git a/gdb/testsuite/gdb.threads/thread-execl.c b/gdb/testsuite/gdb.threads/thread-execl.c
index 403aa3109ca168829414aec6aa1da06907eec83b..2d312d4ea9599f489737d6fac21e50e839933e41 100644 (file)
--- a/gdb/testsuite/gdb.threads/thread-execl.c
+++ b/gdb/testsuite/gdb.threads/thread-execl.c
@@ -25,8 +25,9 @@ static const char *image;
 void *
 thread_execler (void *arg)
 {
-  /* Exec ourselves again.  */
-  if (execl (image, image, NULL) == -1)
+  /* Exec ourselves again.  Pass an extra argument so that the
+     post-exec image knows to not re-exec yet again.  */
+  if (execl (image, image, "1", NULL) == -1)
     {
       perror ("execl");
       abort ();
@@ -40,6 +41,11 @@ main (int argc, char **argv)
 {
   pthread_t thread;
 
+  /* An extra argument means we're in the post-exec image, so we're
+     done.  Don't re-exec again.  */
+  if (argc > 1)
+    exit (0);
+
   image = argv[0];
 
   pthread_create (&thread, NULL, thread_execler, NULL);