[PATCH v4 2/2] gdb/infrun: handle already-exited threads when attempting to stop
Tankut Baris Aktemur
tankut.baris.aktemur@intel.com
Fri Feb 7 12:04:00 GMT 2020
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 --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
--
2.17.1
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