Re: [PATCH with testcase] Bug 11568 - delete thread-specific breakpoint on the thread exit

[Muhammad Waqas <mwaqas at codesourcery dot com>]

On 08/02/2013 02:45 PM, Pedro Alves wrote:
> On 08/01/2013 01:43 PM, Muhammad Waqas wrote:
> > > > > > +			    || !target_thread_alive (tp->ptid)))
> > > > > > +	if ( tp != NULL && (tp->state == THREAD_EXITED
> > > > > > +			    || !target_thread_alive (tp->ptid)))
> > > > Do we really need this target_thread_alive call?  It
> > > > means we have extra remote traffic whenever we have a thread
> > > > specific breakpoint in the list.  If the user (or GDB itself)
> > > > hasn't refreshed the thread list, is there any harm in delaying
> > > > deleting the breakpoint?
> > > >
> > > > But, I think I agree with Yao in that this doesn't look like
> > > > the right way to do this.
> > > >
> > > > In fact, breakpoint_auto_delete is only called when the
> > > > target reports some stop.  If you're trying to delete
> > > > stale thread specific breakpoints, then you'd want to
> > > > do that even if the target hasn't reported a stop, right?
> > > >
> > > > Say, in non-stop mode, w/ the remote target, if you have two
> > > > threads, set a thread-specific break on thread 2, and while
> > > > all threads are running free in busy loops, not reporting
> > > > any event, keep doing "info threads", and "info break".  At some
> > > > point thread #2 exits.  You can see that from "info threads".
> > > > But "info break" will still show you the stale breakpoint...
> > If breakpoint will be deleted when thread list is updated through
> > user or GDB and also when info break command is executed
> > by user, Will it work? What will you say about this technique?
> I wouldn't even consider special casing "info break".  Otherwise,
> you end up considering whether to handle all sorts of breakpoint
> manipulation commands, like "enable", "disable", etc., and what
> to do if the thread is already gone.
>
> Tie this to GDB's own lifetime of the inferior's threads.  If GDB
> learns the thread is gone, remove the breakpoint.  Otherwise,
> leave it there.  Whether to remove the breakpoint immediately,
> or mark it as disp_del_at_next_stop (and hide it, say, set its
> bp->num to 0) is another question.  You'll note that
> clear_thread_inferior_resources does the latter.  (That's because
> most of GDB's native targets can't touch memory of running processes.)

Thanks for review and helping me out.

Now I register a function for deletion of breakpoint with thread_exit if breakpoint
is on thread so breakpoint will be deleted when thread finished.

Changlog

2013-08-05  Muhammad Waqas  <mwaqas@codesourcery.com>

	PR gdb/11568
	* breakpoint.c (remove_threaded_breakpoints): New function.
	* breakpoint.c (install_breakpoint): If breakpoint is on specific
	thread remove_threaded_breakpoints will be registered with thread_exit.


Index: ./../../breakpoint.c
===================================================================
RCS file: /cvs/src/src/gdb/breakpoint.c,v
retrieving revision 1.773
diff -u -p -r1.773 breakpoint.c
--- ./../../breakpoint.c	24 Jul 2013 19:50:32 -0000	1.773
+++ ./../../breakpoint.c	5 Aug 2013 11:51:43 -0000
@@ -200,6 +200,8 @@ typedef enum
   }
 insertion_state_t;
 
+static void remove_threaded_breakpoints (struct thread_info *tp, int silent);
+
 static int remove_breakpoint (struct bp_location *, insertion_state_t);
 static int remove_breakpoint_1 (struct bp_location *, insertion_state_t);
 
@@ -2928,6 +2930,21 @@ remove_breakpoints (void)
   return val;
 }
 
+static void
+remove_threaded_breakpoints(struct thread_info *tp, int silent)
+{
+  struct breakpoint *b, *b_tmp;
+
+  ALL_BREAKPOINTS_SAFE (b, b_tmp)
+    {
+      if (b->thread == tp->num)
+	{
+	  b->disposition = disp_del_at_next_stop;
+	  b->number = 0;
+	}
+    }
+}
+
 /* Remove breakpoints of process PID.  */
 
 int
@@ -8450,7 +8467,12 @@ install_breakpoint (int internal, struct
   if (!internal)
     mention (b);
   observer_notify_breakpoint_created (b);
-
+
+  if (b->thread > 0)
+    {
+      observer_attach_thread_exit (remove_threaded_breakpoints);
+    }
+
   if (update_gll)
     update_global_location_list (1);
 }

Changlog

2013-07-24  Muhammad Waqas  <mwaqas@codesourccery.com>
	    Jan Kratochvil  <jan.kartochvil@redhat.com>

	PR gdb/11568
	*gdb.thread/thread-specific-bp.c: Newfile.
	*gdb.thread/thread-specific-bp.exp: Newfile.


testcase now testing All stop and non stop mode explicitly

Index: thread-specific-bp.c
===================================================================
RCS file: thread-specific-bp.c
diff -N thread-specific-bp.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ thread-specific-bp.c	5 Aug 2013 11:51:51 -0000
@@ -0,0 +1,33 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2013 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/>.  */
+
+#include <pthread.h>
+
+static void *
+start (void *arg)
+{
+  return NULL;
+}
+
+int
+main (void)
+{
+  pthread_t thread;
+  pthread_create (&thread, NULL, start, NULL);
+  pthread_join (thread, NULL);
+  return 0; /*set break here*/
+}
Index: thread-specific-bp.exp
===================================================================
RCS file: thread-specific-bp.exp
diff -N thread-specific-bp.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ thread-specific-bp.exp	5 Aug 2013 11:52:03 -0000
@@ -0,0 +1,84 @@
+# Copyright (C) 2013 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/>.
+#
+# Verify that a thread-specific breakpoint is deleted when the
+# corresponding thread is gone.
+
+standard_testfile
+
+set mode "All stop"
+
+if {[gdb_compile_pthreads \
+	 "${srcdir}/${subdir}/${srcfile}" \
+	 "${binfile}" executable {debug} ] != "" } {
+    return -1
+}
+
+clean_restart ${binfile}
+
+proc check_threaded_breakpoint {} {
+    global gdb_prompt mode
+    gdb_breakpoint "start"
+    gdb_continue_to_breakpoint "start"
+    set thre 0
+    gdb_test_multiple "info threads" "get thread 1 id" {
+	-re "(\[0-9\]+)(\[^\n\r\]*Thread\[^\n\r\]*start.*)($gdb_prompt $)" {
+	    pass "$mode: thread created"
+	    # get the id of thread
+	    set thre $expect_out(1,string)
+	}
+    }
+    gdb_breakpoint [gdb_get_line_number "set break here"]
+
+    # Force GDB to update its knowledge on existing threads when this
+    # breakpoint is hit.  Otherwise, GDB doesn't realize thread $thre
+    # has exited and doesn't remove the thread specific breakpoint.
+    gdb_test "commands\ninfo threads\nend" "End with.*" "$mode: add breakpoint commands"
+    gdb_breakpoint "main thread $thre"
+    gdb_test "info break" ".*breakpoint.*thread $thre" "$mode: Breakpoint set"
+    gdb_test "thread $thre" "Switching to thread $thre.*" "$mode: Thread $thre selected"
+    gdb_continue_to_breakpoint "$mode: set break here"
+    set test "$mode: thread-specific breakpoint is deleted"
+    gdb_test_multiple "info breakpoint" $test {
+    	-re "thread $thre.*$gdb_prompt $" {
+	    fail $test
+    	}
+    	-re "$gdb_prompt $" {
+	    pass $test
+    	}
+    }
+}
+
+if ![runto_main] {
+    untested "could not run to main"
+    return -1
+}
+
+# Testing in all stop mode.
+check_threaded_breakpoint
+
+clean_restart ${binfile}
+
+gdb_test "set target-async on" ".*" "Set async mode"
+gdb_test "set non-stop on" ".*" "Set non stop mode"
+
+if ![runto_main] {
+    untested "could not run to main"
+    return -1
+}
+
+# Testing in non-stop+async mode.
+set mode "non-stop\\async"
+check_threaded_breakpoint