Re: [patch] Fix for internal-error: linux_nat_post_attach_wait: Assertion `pid == new_pid && WIFSTOPPED (status)' failed.

[Paul Pluzhnikov <ppluzhnikov@google.com>]

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On Wed, Oct 14, 2009 at 12:07 PM, Pedro Alves <pedro@codesourcery.com> wrote:

> Ugh.  Happened much more often for me, like 1 in 5...

It's racy. I've seen different frequency of problems depending on
whether I run kernel 2.6.24 or 2.6.30.

> I don't think you needed the interface change.

Indeed.

> Back to the "simple" variant: The inferior just added is
> always inferior_ptid/current_inferior().  If you look
> at fork-child.c:startup_inferior, you'll see bits of
> code doing exactly what you'd need to do.  E.g.:
>
>            target_terminal_ours ();
>            target_mourn_inferior ();
>            if (WIFEXITED (status))
>              error (_("During startup program exited with code %d."),
>                     WIFEXITCODE (status));
>            else if (WIFSIGNALED (status))
>              error (_("During startup program exited with signal ..."),
>                     ...);

I don't see above code in fork-child.c (or anywhere else for that
matter). Are you looking at a local patch?

Anyway, here is try #3.

Thanks,
-- 
Paul Pluzhnikov

2009-10-14  Paul Pluzhnikov  <ppluzhnikov@google.com>

       * linux-nat.c (linux_nat_post_attach_wait): Adjust assert.
       (lin_lwp_attach_lwp, linux_nat_attach): Handle disappearing LWP.

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Index: linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/linux-nat.c,v
retrieving revision 1.151
diff -u -p -u -r1.151 linux-nat.c
--- linux-nat.c	9 Oct 2009 01:57:12 -0000	1.151
+++ linux-nat.c	14 Oct 2009 20:41:46 -0000
@@ -1338,7 +1338,16 @@ linux_nat_post_attach_wait (ptid_t ptid,
       *cloned = 1;
     }
 
-  gdb_assert (pid == new_pid && WIFSTOPPED (status));
+  gdb_assert (pid == new_pid);
+
+  if (!WIFSTOPPED (status))
+    {
+      /* The pid we tried to attach has apparently just exited.  */
+      if (debug_linux_nat)
+	fprintf_unfiltered (gdb_stdlog, "LNPAW: Failed to stop %d: %s",
+			    pid, status_to_str (status));
+      return status;
+    }
 
   if (WSTOPSIG (status) != SIGSTOP)
     {
@@ -1396,6 +1405,9 @@ lin_lwp_attach_lwp (ptid_t ptid)
 			    target_pid_to_str (ptid));
 
       status = linux_nat_post_attach_wait (ptid, 0, &cloned, &signalled);
+      if (!WIFSTOPPED (status))
+	return -1;
+
       lp = add_lwp (ptid);
       lp->stopped = 1;
       lp->cloned = cloned;
@@ -1495,6 +1507,37 @@ linux_nat_attach (struct target_ops *ops
 
   status = linux_nat_post_attach_wait (lp->ptid, 1, &lp->cloned,
 				       &lp->signalled);
+  if (!WIFSTOPPED (status))
+    {
+      delete_lwp (ptid);
+      if (WIFEXITED (status))
+	{
+	  int exit_code = WEXITSTATUS (status);
+
+	  target_terminal_ours ();
+	  target_mourn_inferior ();
+	  if (exit_code == 0)
+	    error (_("During startup program exited normally."));
+	  else
+	    error (_("During startup program exited with code %d."),
+		   exit_code);
+	}
+      else if (WIFSIGNALED (status))
+	{
+	  int signo = WTERMSIG (status);
+
+	  target_terminal_ours ();
+	  target_mourn_inferior ();
+	  error (_("During startup program terminated with signal %s, %s."),
+		 target_signal_to_name (signo),
+		 target_signal_to_string (signo));
+	}
+
+      internal_error (__FILE__, __LINE__,
+		      _("unexpected status %d for PID %ld"),
+		      status, (long) GET_LWP (ptid));
+    }
+
   lp->stopped = 1;
 
   /* Save the wait status to report later.  */