btrace: record stop moves to the end of the trace

With the btrace record target the "record stop" command implicitly moves all
traced threads to the end of their respective history.  Unlike record full,
record btrace does not trace data and is therefore not able to resume debugging
at the current replay position.

We forgot to actually change the replay position before disabling tracing.  This
resulted in STOP_PC remaining at its old position if the current thread had been
replaying, which, in turn, resulted in GDB commands such as list or backtrace
using the wrong context.

Fix it by moving the selected thread to the end of its recorded history.
Together with the preceding patches, this will result in a front-end
notification for the selected thread if it had been replaying.  Stop replaying
other threads silently, i.e. without a front-end notification.

If the selected thread isn't replaying, notify front-ends without printing the
(unchanged) frame.  This results in a *stopped MI notification without any
thread information.

In non-stop mode, move all replaying threads to the end of their respective
histories.  This will result in a front-end notification and in the updated
location to be printed for each replaying thread.  We prefix the output with
the thread number like this:

    (gdb) record stop
    Thread 1 (Thread 0x7ffff7fcc740 (LWP 66711)) stopped replaying.
    test (arg=0x0) at gdb.btrace/multi-thread-step.c:34
    34        global = 42; /* bp.2 */
    Thread 2 (Thread 0x7ffff74fb700 (LWP 66716)) stopped replaying.
    test (arg=0x0) at gdb.btrace/multi-thread-step.c:34
    34        global = 42; /* bp.2 */
    Process record is stopped and all execution logs are deleted.

Thanks to Marc Khouzam <marc.khouzam@ericsson.com> for reporting this.

Signed-off-by: Markus Metzger  <markus.t.metzger@intel.com>

gdb/
	* record-btrace.c (record_btrace_set_replay)
	(record_btrace_stop_replaying): New declaration.
	(record_btrace_stop_recording): Call record_btrace_set_replay,
	record_btrace_stop_replaying, and observer_notify_normal_stop.

testsuite/
	* gdb.btrace/non-stop.exp: Test "record stop".
	* gdb.btrace/non-stop.c (test): Add statement to break at.
	* gdb.btrace/stop.exp: New.

Change-Id: I10565a8e4f8bc3c63f79c3ef6595e9f84e3d8100

gdb/infrun.c

@@ -2785,10 +2785,9 @@ new_stop_id (void)
   current_stop_id++;
 }
 
-/* Clear out all variables saying what to do when inferior is continued.
-   First do this, then set the ones you want, then call `proceed'.  */
+/* See infrun.h.  */
 
-static void
+void
 clear_proceed_status_thread (struct thread_info *tp)
 {
   if (debug_infrun)

gdb/infrun.h

@@ -80,6 +80,9 @@ extern void start_remote (int from_tty);
    step/stepi command.  */
 extern void clear_proceed_status (int step);
 
+/* Clear out the proceed status of TP.  */
+extern void clear_proceed_status_thread (struct thread_info *tp);
+
 extern void proceed (CORE_ADDR, enum gdb_signal);
 
 /* The `resume' routine should only be called in special circumstances.

gdb/record-btrace.c

@@ -97,6 +97,11 @@ static struct cmd_list_element *show_record_btrace_pt_cmdlist;
     }									\
   while (0)
 
+static void record_btrace_set_replay (struct thread_info *tp,
+				      const struct btrace_insn_iterator *it);
+
+static void record_btrace_stop_replaying (struct thread_info *tp);
+
 
 /* Update the branch trace for the current thread and return a pointer to its
    thread_info.
@@ -252,9 +257,57 @@ record_btrace_stop_recording (struct target_ops *self)
 
   record_btrace_auto_disable ();
 
-  ALL_NON_EXITED_THREADS (tp)
-    if (tp->btrace.target != NULL)
-      btrace_disable (tp);
+  /* In non-stop mode, we indicate the implicit move of each replaying thread.
+     In stop-all mode, we indicate the implicit move of the selected thread if
+     it is replaying.  Other threads are silently moved.  The MI notification
+     will indicate that all threads have been stopped which should be enough to
+     indicate this implicit move to front-ends.  */
+  if (non_stop)
+    {
+      ALL_NON_EXITED_THREADS (tp)
+	if (tp->btrace.target != NULL)
+	  {
+	    if (btrace_is_replaying (tp))
+	      {
+		printf_filtered (_("Thread %s (%s) stopped replaying.\n"),
+				 print_thread_id (tp),
+				 target_pid_to_str (tp->ptid));
+		record_btrace_set_replay (tp, NULL);
+	      }
+
+	    btrace_disable (tp);
+	  }
+    }
+  else
+    {
+      int send_stopped = 0;
+
+      /* If the selected thread is replaying, we do an implicit "record goto
+	 end" to make it stop replaying and indicate this to front-ends.  This
+	 causes the updated location to be printed for the selected thread.
+
+	 If it isn't replaying, we will send an unspecific stopped notification
+	 to front-ends at the end.  This doesn't print the (unchanged) location
+	 but indicates to front-ends that other thread's locations may have
+	 changed.  */
+      tp = inferior_thread ();
+      if (tp != NULL && btrace_is_replaying (tp))
+	record_btrace_set_replay (tp, NULL);
+      else
+	send_stopped = 1;
+
+      ALL_NON_EXITED_THREADS (tp)
+	if (tp->btrace.target != NULL)
+	  {
+	    /* Stop replaying before we disable tracing to clear TP's register
+	       state in addition to the btrace state.  */
+	    record_btrace_stop_replaying (tp);
+	    btrace_disable (tp);
+	  }
+
+      if (send_stopped)
+	observer_notify_normal_stop (NULL, 0);
+    }
 }
 
 /* The to_close method of target record-btrace.  */
@@ -2704,7 +2757,12 @@ record_btrace_set_replay (struct thread_info *tp,
   btinfo = &tp->btrace;
 
   if (it == NULL || it->function == NULL)
-    record_btrace_stop_replaying (tp);
+    {
+      if (!btrace_is_replaying (tp))
+	return;
+
+      record_btrace_stop_replaying (tp);
+    }
   else
     {
       if (btinfo->replay == NULL)
@@ -2719,8 +2777,12 @@ record_btrace_set_replay (struct thread_info *tp,
   /* Start anew from the new replay position.  */
   record_btrace_clear_histories (btinfo);
 
-  stop_pc = regcache_read_pc (get_current_regcache ());
-  print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
+  /* We changed the PC of TP.  Update the global state if TP is the selected
+     thread.  */
+  if (ptid_equal (tp->ptid, inferior_ptid))
+    stop_pc = regcache_read_pc (get_current_regcache ());
+
+  record_signal_goto_stop (tp);
 }
 
 /* The to_goto_record_begin method of target record-btrace.  */

gdb/record-full.c

@@ -1905,7 +1905,7 @@ record_full_goto_entry (struct record_full_entry *p)
   registers_changed ();
   reinit_frame_cache ();
   stop_pc = regcache_read_pc (get_current_regcache ());
-  print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
+  record_signal_goto_stop (inferior_thread ());
 }
 
 /* The "to_goto_record_begin" target method.  */

gdb/record.c

@@ -26,6 +26,7 @@
 #include "common/common-utils.h"
 #include "cli/cli-utils.h"
 #include "disasm.h"
+#include "gdbthread.h"
 
 #include <ctype.h>
 
@@ -80,6 +81,16 @@ require_record_target (void)
   return t;
 }
 
+/* Check that the inferior thread is not running.  Throw an error if it is.  */
+
+static void
+require_not_running (void)
+{
+  if (is_running (inferior_ptid))
+    error (_("Cannot execute this command while "
+	     "the selected thread is running."));
+}
+
 /* See record.h.  */
 
 void
@@ -331,6 +342,27 @@ cmd_record_save (char *args, int from_tty)
 
 /* See record.h.  */
 
+void
+record_signal_goto_stop (struct thread_info *tp)
+{
+  struct target_waitstatus ws;
+  struct cleanup *cleanup;
+
+  clear_proceed_status_thread (tp);
+
+  cleanup = make_cleanup_restore_current_thread ();
+  switch_to_thread (tp->ptid);
+
+  ws.kind = TARGET_WAITKIND_NO_RESUMED;
+  set_last_target_status (tp->ptid, ws);
+
+  observer_notify_normal_stop (NULL, 1);
+
+  do_cleanups (cleanup);
+}
+
+/* See record.h.  */
+
 void
 record_goto (const char *arg)
 {
@@ -342,6 +374,7 @@ record_goto (const char *arg)
   insn = parse_and_eval_long (arg);
 
   require_record_target ();
+  require_not_running ();
   target_goto_record (insn);
 }
 
@@ -365,6 +398,7 @@ cmd_record_goto_begin (char *arg, int from_tty)
     error (_("Junk after argument: %s."), arg);
 
   require_record_target ();
+  require_not_running ();
   target_goto_record_begin ();
 }
 
@@ -377,6 +411,7 @@ cmd_record_goto_end (char *arg, int from_tty)
     error (_("Junk after argument: %s."), arg);
 
   require_record_target ();
+  require_not_running ();
   target_goto_record_end ();
 }
 

gdb/record.h

@@ -91,4 +91,7 @@ extern struct target_ops *find_record_target (void);
    it does anything.  */
 extern void record_preopen (void);
 
+/* Signal a record-goto stop of TP to front-ends.  */
+extern void record_signal_goto_stop (struct thread_info *tp);
+
 #endif /* _RECORD_H_ */

gdb/testsuite/gdb.btrace/non-stop.c

@@ -27,7 +27,9 @@ test (void *arg)
   i = 0; /* bp.1 */
   for (; i < 10; ++i) global += i; /* loop */
 
-  return arg; /* bp.2 */
+  global *= 2; /* bp.2 */
+
+  return arg; /* bp.3 */
 }
 
 int
@@ -41,5 +43,5 @@ main (void)
 
   pthread_join (th, NULL);
 
-  return 0; /* bp.3 */
+  return 0;
 }

gdb/testsuite/gdb.btrace/non-stop.exp

@@ -239,7 +239,22 @@ with_test_prefix "no progress" {
 }
 
 # now that both threads stopped replaying we may resume recording
-with_test_prefix "cont to end" {
+with_test_prefix "resume recording" {
     gdb_breakpoint $bp_3
-    gdb_cont_to_bp_line "$srcfile:$bp_3" all 1
+    gdb_cont_to_bp_line "$srcfile:$bp_3" all 2
+}
+
+# when we stop recording we get notifications for replaying threads
+with_test_prefix "stop" {
+    gdb_test "thread 1" ".*"
+    gdb_test "thread apply 2 record goto begin" ".*"
+
+    gdb_test "record stop" [multi_line \
+        "Thread 2 \[^\\\r\\\n\]* stopped replaying\." \
+        "\[^\\\r\\\n\]*$srcfile:$bp_3" \
+        "$bp_3\[^\\\r\\\n\]* bp\.3 \[^\\\r\\\n\]*" \
+        "Process record is stopped and all execution logs are deleted\." \
+    ]
+
+    gdb_test "info record" "No record target is currently active\."
 }

gdb/testsuite/gdb.btrace/record_goto.exp

@@ -160,6 +160,9 @@ gdb_test "record instruction-history -" [multi_line \
 # check that we can go to the end of the trace
 gdb_test "record goto end" ".*main \\(\\) at record_goto.c:50.*"
 
+# check that we don't repeat the current location if we go to the end again
+gdb_test_no_output "record goto end" "goto end again"
+
 # check that we're filling up the context correctly
 gdb_test "record function-call-history /ci" [multi_line \
   "14\t      fun2\tinst 35,36" \

gdb/testsuite/gdb.btrace/stop.exp

@@ -0,0 +1,70 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2016 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/>.
+
+# check for btrace support
+if { [skip_btrace_tests] } { return -1 }
+
+standard_testfile record_goto.c
+
+# start inferior
+if [prepare_for_testing $testfile.exp $testfile $srcfile] {
+	return -1
+}
+
+# we use the list command to check the current source location
+gdb_test "set listsize 1"
+
+if ![runto_main] {
+	return -1
+}
+
+# trace the call to the test function
+gdb_test_no_output "record btrace" "move: enable"
+gdb_test "next" ".*main\.3.*" "move: trace"
+
+# move to the beginning of the trace
+gdb_test "record goto begin" ".*main\.2.*" "move: navigate"
+
+# when we stop recording, we move back to the end of the trace
+gdb_test "record stop" "main\.3.*Process record is stopped.*" "move: stop"
+
+# check that we're really there
+gdb_test "list" ".*main\.3.*" "move: at end of trace"
+
+if ![runto_main] {
+	return -1
+}
+
+# trace the call to the test function
+gdb_test_no_output "record btrace" "already: enable"
+gdb_test "next" ".*main\.3.*" "already: trace"
+
+# we're already at the end so we didn't have to move
+gdb_test_multiple "record stop" "already: stop" {
+	-re "main.*$gdb_prompt $" {
+		fail "already: stop"
+	}
+	-re "Process record is stopped\[^\\\r\\\n\]*\r\n$gdb_prompt $" {
+		pass "already: stop"
+	}
+	-re "$gdb_prompt $" {
+		fail "already: stop"
+	}
+}
+
+# check that we're really there
+gdb_test "list" ".*main\.3.*" "already: at end of trace"

gdb/testsuite/gdb.mi/mi-reverse.exp

@@ -93,6 +93,7 @@ proc test_controlled_execution_reverse {} {
     global line_callee1_head line_callee1_body line_callee1_close
     global line_main_head    line_main_body
     global line_main_hello   line_main_callme_1
+    global line_callme_body
 
     # Test exec-reverse-finish
 
@@ -166,6 +167,14 @@ proc test_controlled_execution_reverse {} {
         "" "main" "" \
         "basics.c" $line_main_body "" \
         "reverse-continue at main"
+
+    send_gdb "record goto end\n"
+    mi_expect_stop "" "callme" "\{name=\"i\",value=\"1\"\}" "basics.c" \
+        $line_callme_body { "" "" "\\^done\r\n" } "record goto end"
+
+    send_gdb "record goto begin\n"
+    mi_expect_stop "" "main" "" "basics.c" $line_main_body \
+        { "" "" "\\^done\r\n" } "record goto begin"
 }
 
 test_controlled_execution_reverse

gdb/testsuite/lib/mi-support.exp

@@ -1127,6 +1127,8 @@ proc mi_detect_async {} {
 # output right after *stopped, and the second element is output
 # right after reason field.  The regex after reason should not include
 # the comma separating it from the following fields.
+# If EXTRA is a list of three elements, the first two are for the above
+# and the third element is for output right before GDB prompt.
 #
 # When we fail to match output at all, -1 is returned.  If FILE does
 # match and the target system has no debug info for FILE return 0.
@@ -1150,7 +1152,15 @@ proc mi_expect_stop { reason func args file line extra test } {
 
     set after_stopped ""
     set after_reason ""
-    if { [llength $extra] == 2 } {
+    set before_prompt ""
+    if { [llength $extra] == 3 } {
+	set after_stopped [lindex $extra 0]
+	set after_reason [lindex $extra 1]
+		if { $after_reason != "" } {
+			set after_reason "${after_reason},"
+		}
+	set before_prompt [lindex $extra 2]
+    } elseif { [llength $extra] == 2 } {
 	set after_stopped [lindex $extra 0]
 	set after_reason [lindex $extra 1]
 	set after_reason "${after_reason},"
@@ -1166,7 +1176,7 @@ proc mi_expect_stop { reason func args file line extra test } {
 
     if { $reason == "really-no-reason" } {
 	gdb_expect {
-	    -re "\\*stopped\r\n$prompt_re" {
+	    -re "\\*stopped\r\n$before_prompt$prompt_re" {
 		pass "$test"
 	    }
 	    timeout {
@@ -1179,7 +1189,7 @@ proc mi_expect_stop { reason func args file line extra test } {
     if { $reason == "exited-normally" } {
 
 	gdb_expect {
-	    -re "\\*stopped,reason=\"exited-normally\"\r\n$prompt_re" {
+	    -re "\\*stopped,reason=\"exited-normally\"\r\n$before_prompt$prompt_re" {
 		pass "$test"
 	    }
 	    -re ".*$mi_gdb_prompt$" {fail "continue to end (2)"}
@@ -1191,7 +1201,7 @@ proc mi_expect_stop { reason func args file line extra test } {
     }
     if { $reason == "exited" } {
 	gdb_expect {
-	    -re "\\*stopped,reason=\"exited\",exit-code=\"\[0-7\]+\"\r\n$prompt_re" {
+	    -re "\\*stopped,reason=\"exited\",exit-code=\"\[0-7\]+\"\r\n$before_prompt$prompt_re" {
 		pass "$test"
 	    }
 	    -re ".*$mi_gdb_prompt$" {
@@ -1205,7 +1215,7 @@ proc mi_expect_stop { reason func args file line extra test } {
     }
 
     if { $reason == "solib-event" } {
-	set pattern "\\*stopped,reason=\"solib-event\",thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$prompt_re"
+	set pattern "\\*stopped,reason=\"solib-event\",thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$before_prompt$prompt_re"
 	verbose -log "mi_expect_stop: expecting: $pattern"
 	gdb_expect {
 	    -re "$pattern" {
@@ -1235,9 +1245,9 @@ proc mi_expect_stop { reason func args file line extra test } {
 
     set a $after_reason
 
-    verbose -log "mi_expect_stop: expecting: \\*stopped,${r}${a}${bn}frame=\{addr=\"$hex\",func=\"$func\",args=$args,(?:file=\"$any$file\",fullname=\"${fullname_syntax}$file\",line=\"$line\"|from=\"$file\")\}$after_stopped,thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$prompt_re"
+    verbose -log "mi_expect_stop: expecting: \\*stopped,${r}${a}${bn}frame=\{addr=\"$hex\",func=\"$func\",args=$args,(?:file=\"$any$file\",fullname=\"${fullname_syntax}$file\",line=\"$line\"|from=\"$file\")\}$after_stopped,thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$before_prompt$prompt_re"
     gdb_expect {
-	-re "\\*stopped,${r}${a}${bn}frame=\{addr=\"$hex\",func=\"$func\",args=$args,(?:file=\"$any$file\",fullname=\"${fullname_syntax}$file\",line=\"($line)\"|from=\"$file\")\}$after_stopped,thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$prompt_re" {
+	-re "\\*stopped,${r}${a}${bn}frame=\{addr=\"$hex\",func=\"$func\",args=$args,(?:file=\"$any$file\",fullname=\"${fullname_syntax}$file\",line=\"($line)\"|from=\"$file\")\}$after_stopped,thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$before_prompt$prompt_re" {
 	    pass "$test"
 	    if {[array names expect_out "2,string"] != ""} {
 		return $expect_out(2,string)
@@ -1245,7 +1255,7 @@ proc mi_expect_stop { reason func args file line extra test } {
 	    # No debug info available but $file does match.
 	    return 0
 	}
-	-re "\\*stopped,${r}${a}${bn}frame=\{addr=\"$hex\",func=\"$any\",args=\[\\\[\{\]$any\[\\\]\}\],file=\"$any\",fullname=\"${fullname_syntax}$any\",line=\"\[0-9\]*\"\}$after_stopped,thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$prompt_re" {
+	-re "\\*stopped,${r}${a}${bn}frame=\{addr=\"$hex\",func=\"$any\",args=\[\\\[\{\]$any\[\\\]\}\],file=\"$any\",fullname=\"${fullname_syntax}$any\",line=\"\[0-9\]*\"\}$after_stopped,thread-id=\"$decimal\",stopped-threads=$any\r\n($thread_selected_re|$breakpoint_re)*$before_prompt$prompt_re" {
 	    verbose -log "got $expect_out(buffer)"
 	    fail "$test (stopped at wrong place)"
 	    return -1