diff mbox

[v4,2/2] gdb/infrun: handle already-exited threads when attempting to stop

Message ID 2aff425c4d358fe95f67c2898bd8f7cd578d5bcb.1581065751.git.tankut.baris.aktemur@intel.com
State New
Headers show

Commit Message

Tankut Baris Aktemur Feb. 7, 2020, 12:04 p.m. UTC
In stop_all_threads, GDB sends signals to other threads in an attempt
to stop them.  While in a typical scenario the expected wait status is
TARGET_WAITKIND_STOPPED, it is possible that the thread GDB attempted
to stop has already terminated.  If so, a waitstatus other than
TARGET_WAITKIND_STOPPED would be received.  Handle this case
appropriately.

If a wait status that denotes thread termination is ignored, GDB goes
into an infinite loop in stop_all_threads.
E.g.:

~~~
$ gdb ./a.out
(gdb) start
...
(gdb) add-inferior -exec ./a.out
...
(gdb) inferior 2
...
(gdb) start
...
(gdb) set schedule-multiple on
(gdb) set debug infrun 2
(gdb) continue
Continuing.
infrun: clear_proceed_status_thread (process 23419)
infrun: clear_proceed_status_thread (process 23703)
infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT)
infrun: proceed: resuming process 23419
infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 23419] at 0x55555555514e
infrun: infrun_async(1)
infrun: prepare_to_wait
infrun: proceed: resuming process 23703
infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 23703] at 0x55555555514e
infrun: prepare_to_wait
infrun: target_wait (-1.0.0, status) =
infrun:   23703.23703.0 [process 23703],
infrun:   status->kind = exited, status = 0
infrun: handle_inferior_event status->kind = exited, status = 0
[Inferior 2 (process 23703) exited normally]
infrun: stop_waiting
infrun: stop_all_threads
infrun: stop_all_threads, pass=0, iterations=0
infrun:   process 23419 executing, need stop
infrun: target_wait (-1.0.0, status) =
infrun:   23419.23419.0 [process 23419],
infrun:   status->kind = exited, status = 0
infrun: stop_all_threads status->kind = exited, status = 0 process 23419
infrun:   process 23419 executing, already stopping
infrun: target_wait (-1.0.0, status) =
infrun:   -1.0.0 [process -1],
infrun:   status->kind = no-resumed
infrun: stop_all_threads status->kind = no-resumed process -1
infrun:   process 23419 executing, already stopping
infrun: target_wait (-1.0.0, status) =
infrun:   -1.0.0 [process -1],
infrun:   status->kind = no-resumed
infrun: stop_all_threads status->kind = no-resumed process -1
infrun:   process 23419 executing, already stopping
infrun: target_wait (-1.0.0, status) =
infrun:   -1.0.0 [process -1],
infrun:   status->kind = no-resumed
infrun: stop_all_threads status->kind = no-resumed process -1
infrun:   process 23419 executing, already stopping
infrun: target_wait (-1.0.0, status) =
infrun:   -1.0.0 [process -1],
infrun:   status->kind = no-resumed
infrun: stop_all_threads status->kind = no-resumed process -1
infrun:   process 23419 executing, already stopping
~~~

And this polling goes on forever.  This patch prevents the infinite
looping behavior.  For the same scenario above, we obtain the
following behavior:

~~~
...
(gdb) continue
Continuing.
infrun: clear_proceed_status_thread (process 8564)
infrun: clear_proceed_status_thread (process 8652)
infrun: proceed (addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT)
infrun: proceed: resuming process 8564
infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 8564] at 0x55555555514e
infrun: infrun_async(1)
infrun: prepare_to_wait
infrun: proceed: resuming process 8652
infrun: resume (step=0, signal=GDB_SIGNAL_0), trap_expected=0, current thread [process 8652] at 0x55555555514e
infrun: prepare_to_wait
infrun: Found 2 inferiors, starting at #0
infrun: target_wait (-1.0.0, status) =
infrun:   8564.8564.0 [process 8564],
infrun:   status->kind = exited, status = 0
infrun: handle_inferior_event status->kind = exited, status = 0
[Inferior 1 (process 8564) exited normally]
infrun: stop_waiting
infrun: stop_all_threads
infrun: stop_all_threads, pass=0, iterations=0
infrun:   process 8652 executing, need stop
infrun: target_wait (-1.0.0, status) =
infrun:   8652.8652.0 [process 8652],
infrun:   status->kind = exited, status = 0
infrun: stop_all_threads status->kind = exited, status = 0 process 8652
infrun: saving status status->kind = exited, status = 0 for 8652.8652.0
infrun:   process 8652 not executing
infrun: stop_all_threads, pass=1, iterations=1
infrun:   process 8652 not executing
infrun: stop_all_threads done
(gdb) infrun: Using pending wait status status->kind = exited, status = 0 for process 8652.
infrun: target_wait (-1.0.0, status) =
infrun:   8652.8652.0 [process 8652],
infrun:   status->kind = exited, status = 0
infrun: handle_inferior_event status->kind = exited, status = 0
[Inferior 2 (process 8652) exited normally]
infrun: stop_waiting
info inferiors
  Num  Description       Connection           Executable
  1    <null>                                 a.out
* 2    <null>                                 a.out
(gdb) info threads
No threads.
(gdb)
~~~

gdb/ChangeLog:
2020-02-05  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>
	    Tom de Vries  <tdevries@suse.de>

	PR threads/25478
	* infrun.c (stop_all_threads): Do NOT ignore
	TARGET_WAITKIND_NO_RESUMED, TARGET_WAITKIND_THREAD_EXITED,
	TARGET_WAITKIND_EXITED, TARGET_WAITKIND_SIGNALLED wait statuses
	received from threads we attempt to stop.

gdb/testsuite/ChangeLog:
2019-11-04  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* gdb.multi/multi-exit.c: New file.
	* gdb.multi/multi-exit.exp: New file.
	* gdb.multi/multi-kill.c: New file.
	* gdb.multi/multi-kill.exp: New file.

Change-Id: I7cec98f40283773b79255d998511da434e9cd408
---
 gdb/infrun.c                           | 38 ++++++++++--
 gdb/testsuite/gdb.multi/multi-exit.c   | 22 +++++++
 gdb/testsuite/gdb.multi/multi-exit.exp | 81 +++++++++++++++++++++++++
 gdb/testsuite/gdb.multi/multi-kill.c   | 34 +++++++++++
 gdb/testsuite/gdb.multi/multi-kill.exp | 84 ++++++++++++++++++++++++++
 5 files changed, 254 insertions(+), 5 deletions(-)
 create mode 100644 gdb/testsuite/gdb.multi/multi-exit.c
 create mode 100644 gdb/testsuite/gdb.multi/multi-exit.exp
 create mode 100644 gdb/testsuite/gdb.multi/multi-kill.c
 create mode 100644 gdb/testsuite/gdb.multi/multi-kill.exp
diff mbox

Patch

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 9224376d05e..58a6da9ec32 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -4799,9 +4799,14 @@  stop_all_threads (void)
 					"infrun:   %s not executing\n",
 					target_pid_to_str (t->ptid).c_str ());
 
-		  /* The thread may be not executing, but still be
-		     resumed with a pending status to process.  */
-		  t->resumed = false;
+		  if ((t->suspend.waitstatus.kind == TARGET_WAITKIND_SIGNALLED
+		       || t->suspend.waitstatus.kind == TARGET_WAITKIND_EXITED)
+		      && t->suspend.waitstatus_pending_p)
+		    ;
+		  else
+		    /* The thread may be not executing, but still be
+		       resumed with a pending status to process.  */
+		    t->resumed = false;
 		}
 	    }
 
@@ -4829,8 +4834,31 @@  stop_all_threads (void)
 	      || event.ws.kind == TARGET_WAITKIND_EXITED
 	      || event.ws.kind == TARGET_WAITKIND_SIGNALLED)
 	    {
-	      /* All resumed threads exited
-		 or one thread/process exited/signalled.  */
+	      /* Eventing target is null if there were no waitable
+		 targets.  */
+	      if (event.target != nullptr)
+		{
+		  thread_info *t = find_thread_ptid (event.target,
+						     event.ptid);
+		  /* Check if this is the first time we see this thread.
+		     Don't bother adding if it individually exited.  */
+		  if (t == nullptr
+		      && event.ws.kind != TARGET_WAITKIND_THREAD_EXITED)
+		    t = add_thread (event.target, event.ptid);
+
+		  if (t != nullptr)
+		    {
+		      /* Set the threads as non-executing to avoid
+			 another stop attempt on them.  */
+		      mark_non_executing_threads (event.target, event.ptid,
+						  event.ws);
+		      save_waitstatus (t, &event.ws);
+		      /* This was cleared in mark_non_executing_threads.
+			 Set it so this pending event is considered by
+			 do_target_wait.  */
+		      t->resumed = true;
+		    }
+		}
 	    }
 	  else
 	    {
diff --git a/gdb/testsuite/gdb.multi/multi-exit.c b/gdb/testsuite/gdb.multi/multi-exit.c
new file mode 100644
index 00000000000..f4825c8a7c1
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/multi-exit.c
@@ -0,0 +1,22 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2020 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/>.  */
+
+int
+main ()
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.multi/multi-exit.exp b/gdb/testsuite/gdb.multi/multi-exit.exp
new file mode 100644
index 00000000000..959f0e8740a
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/multi-exit.exp
@@ -0,0 +1,81 @@ 
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2020 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/>.
+
+# Test receiving TARGET_WAITKIND_EXITED events from multiple
+# inferiors.  In all stop-mode, upon receiving the exit event from one
+# of the inferiors, GDB will try to stop the other inferior, too.  So,
+# a stop request will be sent.  Receiving a TARGET_WAITKIND_EXITED
+# status kind as a response to that stop request instead of a
+# TARGET_WAITKIND_STOPPED should be handled by GDB without problems.
+
+standard_testfile
+
+# This is a test specific for native GDB's ability to stop all
+# threads.
+if {![can_spawn_for_attach]} {
+    return 0
+}
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
+    return -1
+}
+
+gdb_test "add-inferior -exec $binfile" "Added inferior 2.*" \
+    "add the second inferior"
+
+proc test {} {
+    # Start the processes separately.
+    gdb_test_no_output "set schedule-multiple off"
+
+    gdb_test "inferior 1" ".*Switching to inferior 1.*"
+    if {![runto_main]} {
+	fail "starting inferior 1"
+	return -1
+    }
+
+    gdb_test "inferior 2" ".*Switching to inferior 2.*"
+    if {![runto_main]} {
+	fail "starting inferior 2"
+	return -1
+    }
+
+    # Now continue both processes.
+    gdb_test_no_output "set schedule-multiple on"
+
+    # We want GDB to complete the command and return the prompt
+    # instead of going into an infinite loop.
+    # Both inferiors exit.
+    global inferior_exited_re gdb_prompt
+    set count 0
+    gdb_test_multiple "continue" "continue" {
+	-re "$inferior_exited_re normally\]\[\r\n\]+" {
+	    incr count
+	    if {$count == 2} {
+		pass $gdb_test_name
+	    } else {
+		exp_continue
+	    }
+	}
+	-re "$gdb_prompt " {
+	    exp_continue
+	}
+    }
+}
+
+with_test_prefix "iteration 1" test
+# Repeat to also test re-runnability.
+with_test_prefix "iteration 2" test
diff --git a/gdb/testsuite/gdb.multi/multi-kill.c b/gdb/testsuite/gdb.multi/multi-kill.c
new file mode 100644
index 00000000000..3622c499202
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/multi-kill.c
@@ -0,0 +1,34 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2020 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 program is intended to be started outside of gdb, and then
+   attached to by gdb.  */
+
+#include <unistd.h>
+
+int
+main ()
+{
+  /* Don't run forever in case GDB crashes and DejaGNU fails to kill
+     this program.  */
+  alarm (10);
+
+  while (1)
+    ;
+
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.multi/multi-kill.exp b/gdb/testsuite/gdb.multi/multi-kill.exp
new file mode 100644
index 00000000000..6d509d9f0ba
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/multi-kill.exp
@@ -0,0 +1,84 @@ 
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2020 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/>.
+
+# Test receiving TARGET_WAITKIND_SIGNALLED events from multiple
+# inferiors.  In all stop-mode, upon receiving the exit event from one
+# of the inferiors, GDB will try to stop the other inferior, too.  So,
+# a stop request will be sent.  Receiving a TARGET_WAITKIND_SIGNALLED
+# status kind as a response to that stop request instead of a
+# TARGET_WAITKIND_STOPPED should be handled by GDB without problems.
+
+standard_testfile
+
+# This is a test specific for native GDB's ability to stop all
+# threads.
+if {![can_spawn_for_attach]} {
+    return 0
+}
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
+    return -1
+}
+
+gdb_test "add-inferior -exec $binfile" "Added inferior 2.*" \
+    "add the second inferior"
+
+# We want both processes in a running state.
+gdb_test_no_output "set schedule-multiple on"
+
+proc test {} {
+    # Start the programs, attach to them, then kill both from outside.
+    global binfile
+    global gdb_prompt
+
+    set spawn_id_list [spawn_wait_for_attach [list $binfile $binfile]]
+    set test_spawn_id1 [lindex $spawn_id_list 0]
+    set test_spawn_id2 [lindex $spawn_id_list 1]
+    set testpid1 [spawn_id_get_pid $test_spawn_id1]
+    set testpid2 [spawn_id_get_pid $test_spawn_id2]
+
+    gdb_test "inferior 1" ".*Switching to inferior 1.*"
+
+    gdb_test "attach $testpid1" \
+	"Attaching to program: .*, process $testpid1.*(in|at).*" \
+	"attach to program 1"
+
+    gdb_test "inferior 2" ".*Switching to inferior 2.*"
+
+    gdb_test "attach $testpid2" \
+	"Attaching to program: .*, process $testpid2.*(in|at).*" \
+	"attach to program 2"
+
+    gdb_test_multiple "continue" "continue processes" {
+	-re "Continuing.\[\r\n\]+" {
+	    # Kill both processes at once.
+	    remote_exec build "kill -9 ${testpid1} ${testpid2}"
+	    exp_continue
+	}
+	-re "Program terminated with signal.*$gdb_prompt" {
+	    pass $gdb_test_name
+	}
+    }
+
+    # Make sure that the processes are gone.
+    kill_wait_spawned_process $test_spawn_id1
+    kill_wait_spawned_process $test_spawn_id2
+}
+
+with_test_prefix "iteration 1" test
+# Repeat to also test re-runnability.
+with_test_prefix "iteration 2" test