[RFA] fix crash when rerunning programs in non-stop mode

[dje at google dot com (Doug Evans)]

Hi.

I noticed a patch that recently went in to fix
do_restore_current_thread_cleanup's handling of restoring
the current thread if the program exited.
Good timing because I've been playing with gdb crashes in this area.

The patch does this:

  if (tp
      && is_exited (tp->ptid)
      && find_inferior_pid (ptid_get_pid (tp->ptid)) == NULL)
    restore_current_thread (null_ptid);
  else
    restore_current_thread (old->inferior_ptid);

One problem is that calling is_exited is problematic if
! target_has_execution (this one I'm tripping over).
Another problem is if tp == NULL, then old->inferior_ptid
is restored (this is just an observation).

This patch reverses the sense of what's being tested,
i.e. check for whether old->inferior_ptid restorable
instead of whether it's dead.

Ok to check in?
Included is a testcase to exercise the problem.

2009-03-26  Doug Evans  <dje@google.com>

	* thread.c (do_restore_current_thread_cleanup): Redo test for
	whether to restore old->inferior_ptid.

	* gdb.mi/mi-nonstop-exit.exp: New file.
	* gdb.mi/non-stop-exit.c: New file.

Index: thread.c
===================================================================
RCS file: /cvs/src/src/gdb/thread.c,v
retrieving revision 1.107
diff -u -p -u -p -r1.107 thread.c
--- thread.c	26 Mar 2009 21:30:26 -0000	1.107
+++ thread.c	27 Mar 2009 00:32:30 -0000
@@ -924,11 +924,10 @@ do_restore_current_thread_cleanup (void 
      then don't revert back to it, but instead simply drop back to no
      thread selected.  */
   if (tp
-      && is_exited (tp->ptid)
-      && find_inferior_pid (ptid_get_pid (tp->ptid)) == NULL)
-    restore_current_thread (null_ptid);
-  else
+      && find_inferior_pid (ptid_get_pid (tp->ptid)) != NULL)
     restore_current_thread (old->inferior_ptid);
+  else
+    restore_current_thread (null_ptid);
 
   /* The running state of the originally selected thread may have
      changed, so we have to recheck it here.  */
Index: testsuite/gdb.mi/mi-nonstop-exit.exp
===================================================================
RCS file: testsuite/gdb.mi/mi-nonstop-exit.exp
diff -N testsuite/gdb.mi/mi-nonstop-exit.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.mi/mi-nonstop-exit.exp	27 Mar 2009 00:40:04 -0000
@@ -0,0 +1,106 @@
+# Copyright 2009
+# Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This only works with native configurations
+if {![isnative]} {
+  return
+}
+
+load_lib mi-support.exp
+set MIFLAGS "-i=mi"
+
+gdb_exit
+if {[mi_gdb_start]} {
+    continue
+}
+
+#
+# Start here
+#
+set testfile "non-stop-exit"
+set srcfile "$testfile.c"
+set binfile "$objdir/$subdir/mi-$testfile"
+
+set options [list debug incdir=$objdir]
+if {[gdb_compile_pthreads "$srcdir/$subdir/$srcfile" $binfile executable $options] != "" } {
+    return -1
+}
+
+mi_gdb_reinitialize_dir $srcdir/$subdir
+mi_gdb_load $binfile
+
+set supported 0
+send_gdb "-gdb-show non-stop\n"
+gdb_expect {
+    -re ".*\\^done,value=\"off\",supported=\"(\[^\"\]+)\"\r\n$mi_gdb_prompt$" {
+        if { $expect_out(1,string) == "1" } {
+            set supported 1
+        }
+    }
+    -re ".$mi_gdb_prompt$" {
+    }
+}
+
+mi_gdb_test "-gdb-set non-stop 1" ".*"
+mi_gdb_test "-gdb-set target-async 1" ".*"
+detect_async
+
+mi_gdb_test "200-break-insert -t main" ".*"
+
+set created "=thread-created,id=\"$decimal\"\r\n"
+set running "\\*running,thread-id=\"$decimal\"\r\n"
+
+set notifs "($created)*($running)*($library_loaded_re)*"
+
+# Note: presently, we skip this test on non-native targets,
+# so 'run' is OK.  As soon as we start to run this on remote
+# target, the logic from mi_run_cmd will have to be refactored.
+send_gdb "-exec-run\n"
+gdb_expect {
+    -re "\\^running\r\n$notifs$mi_gdb_prompt" {
+    }
+    -re "\\^error,msg=\"The target does not support running in non-stop mode.\"" {
+        verbose -log "Non-stop mode not supported, skipping all tests"
+        return
+    }
+    -re "\r\n$mi_gdb_prompt" {
+        perror "Cannot start target (unknown output after running)"
+        return -1
+    }
+    timeout {
+        perror "Cannot start target (timeout)"
+        return -1
+    }
+}
+mi_expect_stop "breakpoint-hit" main ".*" ".*" "\[0-9\]+" { "" "disp=\"del\"" } "run to main"
+
+mi_send_resuming_command "exec-continue" "continue"
+
+mi_expect_stop "exited-normally" "" "" "" "" "" "finished exec continue"
+
+# Run the program again.
+
+mi_gdb_test "200-break-insert -t main" ".*"
+
+mi_send_resuming_command "exec-run" "run (2)"
+
+mi_expect_stop "breakpoint-hit" main ".*" ".*" "\[0-9\]+" { "" "disp=\"del\"" } "run to main (2)"
+
+mi_send_resuming_command "exec-continue" "continue (2)"
+
+mi_expect_stop "exited-normally" "" "" "" "" "" "finished exec continue (2)"
+
+mi_gdb_exit
Index: testsuite/gdb.mi/non-stop-exit.c
===================================================================
RCS file: testsuite/gdb.mi/non-stop-exit.c
diff -N testsuite/gdb.mi/non-stop-exit.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.mi/non-stop-exit.c	27 Mar 2009 00:40:04 -0000
@@ -0,0 +1,54 @@
+/* Test program exit in non-stop mode.
+   Copyright 2009 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <pthread.h>
+#include <stdio.h>
+
+#define NTHREADS 4
+void* thread_function (void*);
+
+void *
+thread_function (void *arg)
+{
+  int x = * (int *) arg;
+
+  printf ("Thread <%d> executing\n", x);
+
+  return NULL;
+}
+
+int
+main ()
+{
+  pthread_t thread_id[NTHREADS];
+  int args[NTHREADS];
+  int i;
+
+  for (i = 0; i < NTHREADS; ++i)
+    {
+      args[i] = i;
+      pthread_create (&thread_id[i], NULL, thread_function, &args[i]);
+    }
+
+  for (i = 0; i < NTHREADS; ++i)
+    {
+      pthread_join (thread_id[i], NULL); 
+    }
+
+  return 0;
+}