ptid_t process_stop_reply (struct stop_reply *stop_reply,
target_waitstatus *status);
+ ptid_t select_thread_for_ambiguous_stop_reply
+ (const struct target_waitstatus *status);
+
void remote_notice_new_inferior (ptid_t currthread, int executing);
void process_initial_stop_replies (int from_tty);
remote->remote_notif_get_pending_events (nc);
}
-/* Called when it is decided that STOP_REPLY holds the info of the
- event that is to be returned to the core. This function always
- destroys STOP_REPLY. */
+/* Called from process_stop_reply when the stop packet we are responding
+ to didn't include a process-id or thread-id. STATUS is the stop event
+ we are responding to.
+
+ It is the task of this function to select a suitable thread (or process)
+ and return its ptid, this is the thread (or process) we will assume the
+ stop event came from.
+
+ In some cases there isn't really any choice about which thread (or
+ process) is selected, a basic remote with a single process containing a
+ single thread might choose not to send any process-id or thread-id in
+ its stop packets, this function will select and return the one and only
+ thread.
+
+ However, if a target supports multiple threads (or processes) and still
+ doesn't include a thread-id (or process-id) in its stop packet then
+ first, this is a badly behaving target, and second, we're going to have
+ to select a thread (or process) at random and use that. This function
+ will print a warning to the user if it detects that there is the
+ possibility that GDB is guessing which thread (or process) to
+ report.
+
+ Note that this is called before GDB fetches the updated thread list from the
+ target. So it's possible for the stop reply to be ambiguous and for GDB to
+ not realize it. For example, if there's initially one thread, the target
+ spawns a second thread, and then sends a stop reply without an id that
+ concerns the first thread. GDB will assume the stop reply is about the
+ first thread - the only thread it knows about - without printing a warning.
+ Anyway, if the remote meant for the stop reply to be about the second thread,
+ then it would be really broken, because GDB doesn't know about that thread
+ yet. */
ptid_t
-remote_target::process_stop_reply (struct stop_reply *stop_reply,
- struct target_waitstatus *status)
+remote_target::select_thread_for_ambiguous_stop_reply
+ (const struct target_waitstatus *status)
{
- ptid_t ptid;
+ /* Some stop events apply to all threads in an inferior, while others
+ only apply to a single thread. */
+ bool process_wide_stop
+ = (status->kind == TARGET_WAITKIND_EXITED
+ || status->kind == TARGET_WAITKIND_SIGNALLED);
- *status = stop_reply->ws;
- ptid = stop_reply->ptid;
+ thread_info *first_resumed_thread = nullptr;
+ bool ambiguous = false;
- /* If no thread/process was reported by the stub then use the first
- non-exited thread in the current target. */
- if (ptid == null_ptid)
+ /* Consider all non-exited threads of the target, find the first resumed
+ one. */
+ for (thread_info *thr : all_non_exited_threads (this))
{
- /* Some stop events apply to all threads in an inferior, while others
- only apply to a single thread. */
- bool is_stop_for_all_threads
- = (status->kind == TARGET_WAITKIND_EXITED
- || status->kind == TARGET_WAITKIND_SIGNALLED);
+ remote_thread_info *remote_thr = get_remote_thread_info (thr);
- for (thread_info *thr : all_non_exited_threads (this))
+ if (remote_thr->resume_state () != resume_state::RESUMED)
+ continue;
+
+ if (first_resumed_thread == nullptr)
+ first_resumed_thread = thr;
+ else if (!process_wide_stop
+ || first_resumed_thread->ptid.pid () != thr->ptid.pid ())
+ ambiguous = true;
+ }
+
+ gdb_assert (first_resumed_thread != nullptr);
+
+ /* Warn if the remote target is sending ambiguous stop replies. */
+ if (ambiguous)
+ {
+ static bool warned = false;
+
+ if (!warned)
{
- if (ptid != null_ptid
- && (!is_stop_for_all_threads
- || ptid.pid () != thr->ptid.pid ()))
- {
- static bool warned = false;
+ /* If you are seeing this warning then the remote target has
+ stopped without specifying a thread-id, but the target
+ does have multiple threads (or inferiors), and so GDB is
+ having to guess which thread stopped.
- if (!warned)
- {
- /* If you are seeing this warning then the remote target
- has stopped without specifying a thread-id, but the
- target does have multiple threads (or inferiors), and
- so GDB is having to guess which thread stopped.
-
- Examples of what might cause this are the target
- sending and 'S' stop packet, or a 'T' stop packet and
- not including a thread-id.
-
- Additionally, the target might send a 'W' or 'X
- packet without including a process-id, when the target
- has multiple running inferiors. */
- if (is_stop_for_all_threads)
- warning (_("multi-inferior target stopped without "
- "sending a process-id, using first "
- "non-exited inferior"));
- else
- warning (_("multi-threaded target stopped without "
- "sending a thread-id, using first "
- "non-exited thread"));
- warned = true;
- }
- break;
- }
+ Examples of what might cause this are the target sending
+ and 'S' stop packet, or a 'T' stop packet and not
+ including a thread-id.
- /* If this is a stop for all threads then don't use a particular
- threads ptid, instead create a new ptid where only the pid
- field is set. */
- if (is_stop_for_all_threads)
- ptid = ptid_t (thr->ptid.pid ());
+ Additionally, the target might send a 'W' or 'X packet
+ without including a process-id, when the target has
+ multiple running inferiors. */
+ if (process_wide_stop)
+ warning (_("multi-inferior target stopped without "
+ "sending a process-id, using first "
+ "non-exited inferior"));
else
- ptid = thr->ptid;
+ warning (_("multi-threaded target stopped without "
+ "sending a thread-id, using first "
+ "non-exited thread"));
+ warned = true;
}
- gdb_assert (ptid != null_ptid);
}
+ /* If this is a stop for all threads then don't use a particular threads
+ ptid, instead create a new ptid where only the pid field is set. */
+ if (process_wide_stop)
+ return ptid_t (first_resumed_thread->ptid.pid ());
+ else
+ return first_resumed_thread->ptid;
+}
+
+/* Called when it is decided that STOP_REPLY holds the info of the
+ event that is to be returned to the core. This function always
+ destroys STOP_REPLY. */
+
+ptid_t
+remote_target::process_stop_reply (struct stop_reply *stop_reply,
+ struct target_waitstatus *status)
+{
+ *status = stop_reply->ws;
+ ptid_t ptid = stop_reply->ptid;
+
+ /* If no thread/process was reported by the stub then select a suitable
+ thread/process. */
+ if (ptid == null_ptid)
+ ptid = select_thread_for_ambiguous_stop_reply (status);
+ gdb_assert (ptid != null_ptid);
+
if (status->kind != TARGET_WAITKIND_EXITED
&& status->kind != TARGET_WAITKIND_SIGNALLED
&& status->kind != TARGET_WAITKIND_NO_RESUMED)
--- /dev/null
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2021 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 how GDB handles the case where a target either doesn't use 'T'
+# packets at all or doesn't include a thread-id in a 'T' packet, AND,
+# where the test program contains multiple threads.
+#
+# In general if multiple threads are executing and the target doesn't
+# include a thread-id in its stop response then GDB will not be able
+# to correctly figure out which thread the stop applies to.
+#
+# However, this test covers a very specific case, there are multiple
+# threads but only a single thread is actually executing. So, when
+# the stop comes from the target, without a thread-id, GDB should be
+# able to correctly figure out which thread has stopped.
+
+load_lib gdbserver-support.exp
+
+if { [skip_gdbserver_tests] } {
+ verbose "skipping gdbserver tests"
+ return -1
+}
+
+standard_testfile
+if { [build_executable "failed to prepare" $testfile $srcfile {debug pthreads}] == -1 } {
+ return -1
+}
+
+# Run the tests with different features of GDBserver disabled.
+proc run_test { disable_feature } {
+ global binfile gdb_prompt decimal hex
+
+ clean_restart ${binfile}
+
+ # Make sure we're disconnected, in case we're testing with an
+ # extended-remote board, therefore already connected.
+ gdb_test "disconnect" ".*"
+
+ set packet_arg ""
+ if { $disable_feature != "" } {
+ set packet_arg "--disable-packet=${disable_feature}"
+ }
+ set res [gdbserver_start $packet_arg $binfile]
+ set gdbserver_protocol [lindex $res 0]
+ set gdbserver_gdbport [lindex $res 1]
+
+ # Disable XML-based thread listing, and multi-process extensions.
+ gdb_test_no_output "set remote threads-packet off"
+ gdb_test_no_output "set remote multiprocess-feature-packet off"
+
+ set res [gdb_target_cmd $gdbserver_protocol $gdbserver_gdbport]
+ if ![gdb_assert {$res == 0} "connect"] {
+ return
+ }
+
+ # There should be only one thread listed at this point.
+ gdb_test_multiple "info threads" "" {
+ -re "2 Thread.*$gdb_prompt $" {
+ fail $gdb_test_name
+ }
+ -re "has terminated.*$gdb_prompt $" {
+ fail $gdb_test_name
+ }
+ -re "\\\* 1\[\t \]*Thread\[^\r\n\]*\r\n$gdb_prompt $" {
+ pass $gdb_test_name
+ }
+ }
+
+ gdb_breakpoint "unlock_worker"
+ gdb_continue_to_breakpoint "run to unlock_worker"
+
+ # There should be two threads at this point with thread 1 selected.
+ gdb_test "info threads" \
+ "\\\* 1\[\t \]*Thread\[^\r\n\]*\r\n 2\[\t \]*Thread\[^\r\n\]*" \
+ "second thread should now exist"
+
+ # Switch threads.
+ gdb_test "thread 2" ".*" "switch to second thread"
+
+ # Now turn on scheduler-locking so that when we step thread 2 only
+ # that one thread will be set running.
+ gdb_test_no_output "set scheduler-locking on"
+
+ # Single step thread 2. Only the one thread will step. When the
+ # thread stops, if the stop packet doesn't include a thread-id
+ # then GDB should still understand which thread stopped.
+ gdb_test_multiple "stepi" "" {
+ -re -wrap "Thread 1 received signal SIGTRAP.*" {
+ fail $gdb_test_name
+ }
+ -re -wrap "$hex.*$decimal.*while \\(worker_blocked\\).*" {
+ pass $gdb_test_name
+ }
+ }
+
+ # Check that thread 2 is still selected.
+ gdb_test "info threads" \
+ " 1\[\t \]*Thread\[^\r\n\]*\r\n\\\* 2\[\t \]*Thread\[^\r\n\]*" \
+ "second thread should still be selected after stepi"
+
+ # Turn scheduler locking off again so that when we continue all
+ # threads will be set running.
+ gdb_test_no_output "set scheduler-locking off"
+
+ # Continue until exit. The server sends a 'W' with no PID.
+ # Bad GDB gave an error like below when target is nonstop:
+ # (gdb) c
+ # Continuing.
+ # No process or thread specified in stop reply: W00
+ gdb_continue_to_end "" continue 1
+}
+
+# Disable different features within gdbserver:
+#
+# Tthread: Start GDBserver, with ";thread:NNN" in T stop replies disabled,
+# emulating old gdbservers when debugging single-threaded programs.
+#
+# T: Start GDBserver with the entire 'T' stop reply packet disabled,
+# GDBserver will instead send the 'S' stop reply.
+foreach_with_prefix to_disable { "" Tthread T } {
+ run_test $to_disable
+}
projects / binutils-gdb.git / commitdiff