PR threads/18127 - threads spawned by infcall end up stuck in "running" state

Refs:
 https://sourceware.org/ml/gdb/2015-03/msg00024.html
 https://sourceware.org/ml/gdb/2015-06/msg00005.html

On GNU/Linux, if an infcall spawns a thread, that thread ends up with
stuck running state.  This happens because:

 - when linux-nat.c detects a new thread, it marks them as running,
   and does not report anything to the core.

 - we skip finish_thread_state when the thread that is running the
   infcall stops.

As result, that new thread ends up with stuck "running" state, even
though it really is stopped.

On Windows, _all_ threads end up stuck in running state, not just the
one that was spawned.  That happens because when a new thread is
detected, unlike linux-nat.c, windows-nat.c reports
TARGET_WAITKIND_SPURIOUS to infrun.  It's the fact that that event
does not cause a user-visible stop that triggers the problem.  When
the target is re-resumed, we call set_running with a wildcard ptid,
which marks all thread as running.  That set_running is not suppressed
because the (leader) thread being resumed does not have in_infcall
set.  Later, when the infcall finally finishes successfully, nothing
marks all threads back to stopped.

We can trigger the same problem on all targets by having a thread
other than the one that is running the infcall report a breakpoint hit
to infrun, and then have that breakpoint not cause a stop.  That's
what the included test does.

The fix is to stop GDB from suppressing the set_running calls while
doing an infcall, and then set the threads back to stopped when the
call finishes, iff they were originally stopped before the infcall
started.  (Note the MI *running/*stopped event suppression isn't
affected.)

Tested on x86_64 GNU/Linux.

gdb/ChangeLog:
2015-06-29  Pedro Alves  <palves@redhat.com>

	PR threads/18127
	* infcall.c (run_inferior_call): On infcall success, if the thread
	was marked stopped before, reset it back to stopped.
	* infrun.c (resume): Don't suppress the set_running calls when
	doing an infcall.
	(normal_stop): Only discard the finish_thread_state cleanup if the
	infcall succeeded.

gdb/testsuite/ChangeLog:
2015-06-29  Pedro Alves  <palves@redhat.com>

	PR threads/18127
	* gdb.threads/hand-call-new-thread.c: New file.
	* gdb.threads/hand-call-new-thread.c: New file.

3 files changed, 104 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 89d8e32..d9ec546 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-29  Pedro Alves  <palves@redhat.com>
+
+	PR threads/18127
+	* gdb.threads/hand-call-new-thread.c: New file.
+	* gdb.threads/hand-call-new-thread.c: New file.
+
 2015-06-26  Keith Seitz  <keiths@redhat.com>
 	    Doug Evans  <dje@google.com>
 
diff --git a/gdb/testsuite/gdb.threads/hand-call-new-thread.c b/gdb/testsuite/gdb.threads/hand-call-new-thread.c
new file mode 100644
index 0000000..042be9b
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/hand-call-new-thread.c
@@ -0,0 +1,50 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 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 <unistd.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <assert.h>
+
+static int
+foo (void)
+{
+  usleep (1);
+}
+
+static void *
+thread_function (void *arg)
+{
+  while (1)
+    foo ();
+}
+
+void
+new_thread (void)
+{
+  pthread_t thread;
+  int res;
+
+  res = pthread_create (&thread, NULL, thread_function, NULL);
+  assert (res == 0);
+}
+
+int
+main (int argc, char **argv)
+{
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/hand-call-new-thread.exp b/gdb/testsuite/gdb.threads/hand-call-new-thread.exp
new file mode 100644
index 0000000..a02d8ba
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/hand-call-new-thread.exp
@@ -0,0 +1,48 @@
+# Copyright (C) 2015 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/>.
+
+# Ensure that new threads created while an infcall is ongoing are set
+# to stopped state once the call finishes.
+
+standard_testfile
+
+if [prepare_for_testing "failed to prepare" $testfile $srcfile {debug pthreads}] {
+    return -1
+}
+
+if ![runto_main] {
+    continue
+}
+
+# Set a thread-specific breakpoint that the wrong thread trips on
+# while running the infcall.  Check that no thread ends up in stale
+# "running" state once the call finishes.
+gdb_test "b foo thread 1" "Breakpoint .*$srcfile.*"
+
+for {set i 0} {$i < 3} {incr i} {
+    with_test_prefix "iter $i" {
+	gdb_test "p new_thread ()" " = void"
+
+	set message "no thread marked running"
+	gdb_test_multiple "info threads" $message {
+	    -re "\\\(running\\\).*$gdb_prompt $" {
+		fail $message
+	    }
+	    -re "$gdb_prompt $" {
+		pass $message
+	    }
+	}
+    }
+}