gdb/

2012-06-28  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* gdbthread.h (ALL_THREADS): New macro.
	(thread_list): Declare.
	* infrun.c (handle_inferior_event) <spurious signal>: Don't keep
	going, but instead fall through to the stepping handling.
	* linux-nat.c (resume_lwp): New parameter 'signo'.  Resume with
	the passed in signal.  Adjust debug output.
	(resume_callback): Rename to ...
	(linux_nat_resume_callback): ... this.  Pass the thread's last
	stop signal, if in "pass" state.
	(linux_nat_resume): Adjust to rename.
	(stop_wait_callback): New assertion.  Don't respawn signals;
	instead let the LWP remain with SIGNALLED set.
	(linux_nat_wait_1): Remove flushing of pending SIGSTOPs.
	* remote.c (append_pending_thread_resumptions): New.
	(remote_vcont_resume): Call it.
	* target.h (target_resume): Extend comment.

gdb/testsuite/
2012-06-28  Jan Kratochvil  <jan.kratochvil@redhat.com>
	    Pedro Alves  <palves@redhat.com>

	* gdb.threads/siginfo-threads.exp: New file.
	* gdb.threads/siginfo-threads.c: New file.
	* gdb.threads/sigstep-threads.exp: New file.
	* gdb.threads/sigstep-threads.c: New file.

4 files changed, 683 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.threads/siginfo-threads.c b/gdb/testsuite/gdb.threads/siginfo-threads.c
new file mode 100644
index 0000000..5859088
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/siginfo-threads.c
@@ -0,0 +1,457 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2010-2012 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/>.  */
+
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <stdio.h>
+#include <limits.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <sys/types.h>
+#include <signal.h>
+#include <unistd.h>
+#include <asm/unistd.h>
+
+#define gettid() syscall (__NR_gettid)
+#define tgkill(tgid, tid, sig) syscall (__NR_tgkill, tgid, tid, sig)
+
+/* Terminate always in the main task.  It can lock up with SIGSTOPped
+   GDB otherwise.  */
+#define TIMEOUT (gettid () == getpid() ? 10 : 15)
+
+static pid_t thread1_tid;
+static pthread_cond_t thread1_tid_cond
+  = PTHREAD_COND_INITIALIZER;
+static pthread_mutex_t thread1_tid_mutex
+  = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
+static int thread1_sigusr1_hit;
+static int thread1_sigusr2_hit;
+
+static pid_t thread2_tid;
+static pthread_cond_t thread2_tid_cond
+  = PTHREAD_COND_INITIALIZER;
+static pthread_mutex_t thread2_tid_mutex
+  = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
+static int thread2_sigusr1_hit;
+static int thread2_sigusr2_hit;
+
+static pthread_mutex_t terminate_mutex
+  = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
+
+/* Do not use alarm as it would create a ptrace event which would hang
+   us up if we are being traced by GDB, which we stopped
+   ourselves.  */
+
+static void
+timed_mutex_lock (pthread_mutex_t *mutex)
+{
+  int i;
+  struct timespec start, now;
+
+  i = clock_gettime (CLOCK_MONOTONIC, &start);
+  assert (i == 0);
+
+  do
+    {
+      i = pthread_mutex_trylock (mutex);
+      if (i == 0)
+	return;
+      assert (i == EBUSY);
+
+      i = clock_gettime (CLOCK_MONOTONIC, &now);
+      assert (i == 0);
+      assert (now.tv_sec >= start.tv_sec);
+    }
+  while (now.tv_sec - start.tv_sec < TIMEOUT);
+
+  fprintf (stderr, "Timed out waiting for internal lock!\n");
+  exit (EXIT_FAILURE);
+}
+
+static void
+handler (int signo, siginfo_t *siginfo, void *exception)
+{
+  int *varp;
+
+  assert (siginfo->si_signo == signo);
+  assert (siginfo->si_code == SI_TKILL);
+  assert (siginfo->si_pid == getpid ());
+
+  if (gettid () == thread1_tid)
+    {
+      if (signo == SIGUSR1)
+	varp = &thread1_sigusr1_hit;
+      else if (signo == SIGUSR2)
+	varp = &thread1_sigusr2_hit;
+      else
+	assert (0);
+    }
+  else if (gettid () == thread2_tid)
+    {
+      if (signo == SIGUSR1)
+	varp = &thread2_sigusr1_hit;
+      else if (signo == SIGUSR2)
+	varp = &thread2_sigusr2_hit;
+      else
+	assert (0);
+    }
+  else
+    assert (0);
+
+  if (*varp)
+    {
+      fprintf (stderr, "Signal %d for TID %lu has been already hit!\n", signo,
+	       (unsigned long) gettid ());
+      exit (EXIT_FAILURE);
+    }
+  *varp = 1;
+}
+
+static void *
+thread1_func (void *unused)
+{
+  int i;
+
+  timed_mutex_lock (&thread1_tid_mutex);
+
+  /* THREAD1_TID_MUTEX must be already locked to avoid a race.  */
+  thread1_tid = gettid ();
+
+  i = pthread_cond_signal (&thread1_tid_cond);
+  assert (i == 0);
+  i = pthread_mutex_unlock (&thread1_tid_mutex);
+  assert (i == 0);
+
+  /* Be sure the "t (tracing stop)" test can proceed for both
+     threads.  */
+  timed_mutex_lock (&terminate_mutex);
+  i = pthread_mutex_unlock (&terminate_mutex);
+  assert (i == 0);
+
+  if (!thread1_sigusr1_hit)
+    {
+      fprintf (stderr, "Thread 1 signal SIGUSR1 not hit!\n");
+      exit (EXIT_FAILURE);
+    }
+  if (!thread1_sigusr2_hit)
+    {
+      fprintf (stderr, "Thread 1 signal SIGUSR2 not hit!\n");
+      exit (EXIT_FAILURE);
+    }
+
+  return NULL;
+}
+
+static void *
+thread2_func (void *unused)
+{
+  int i;
+
+  timed_mutex_lock (&thread2_tid_mutex);
+
+  /* THREAD2_TID_MUTEX must be already locked to avoid a race.  */
+  thread2_tid = gettid ();
+
+  i = pthread_cond_signal (&thread2_tid_cond);
+  assert (i == 0);
+  i = pthread_mutex_unlock (&thread2_tid_mutex);
+  assert (i == 0);
+
+  /* Be sure the "t (tracing stop)" test can proceed for both
+     threads.  */
+  timed_mutex_lock (&terminate_mutex);
+  i = pthread_mutex_unlock (&terminate_mutex);
+  assert (i == 0);
+
+  if (!thread2_sigusr1_hit)
+    {
+      fprintf (stderr, "Thread 2 signal SIGUSR1 not hit!\n");
+      exit (EXIT_FAILURE);
+    }
+  if (!thread2_sigusr2_hit)
+    {
+      fprintf (stderr, "Thread 2 signal SIGUSR2 not hit!\n");
+      exit (EXIT_FAILURE);
+    }
+
+  return NULL;
+}
+
+static const char *
+proc_string (const char *filename, const char *line)
+{
+  FILE *f;
+  static char buf[LINE_MAX];
+  size_t line_len = strlen (line);
+
+  f = fopen (filename, "r");
+  if (f == NULL)
+    {
+      fprintf (stderr, "fopen (\"%s\") for \"%s\": %s\n", filename, line,
+	       strerror (errno));
+      exit (EXIT_FAILURE);
+    }
+  while (errno = 0, fgets (buf, sizeof (buf), f))
+    {
+      char *s;
+
+      s = strchr (buf, '\n');
+      assert (s != NULL);
+      *s = 0;
+
+      if (strncmp (buf, line, line_len) != 0)
+	continue;
+
+      if (fclose (f))
+	{
+	  fprintf (stderr, "fclose (\"%s\") for \"%s\": %s\n", filename, line,
+		   strerror (errno));
+	  exit (EXIT_FAILURE);
+	}
+
+      return &buf[line_len];
+    }
+  if (errno != 0)
+    {
+      fprintf (stderr, "fgets (\"%s\": %s\n", filename, strerror (errno));
+      exit (EXIT_FAILURE);
+    }
+  fprintf (stderr, "\"%s\": No line \"%s\" found.\n", filename, line);
+  exit (EXIT_FAILURE);
+}
+
+static unsigned long
+proc_ulong (const char *filename, const char *line)
+{
+  const char *s = proc_string (filename, line);
+  long retval;
+  char *end;
+
+  errno = 0;
+  retval = strtol (s, &end, 10);
+  if (retval < 0 || retval >= LONG_MAX || (end && *end))
+    {
+      fprintf (stderr, "\"%s\":\"%s\": %ld, %s\n", filename, line, retval,
+	       strerror (errno));
+      exit (EXIT_FAILURE);
+    }
+  return retval;
+}
+
+static void
+state_wait (pid_t process, const char *wanted)
+{
+  char *filename;
+  int i;
+  struct timespec start, now;
+  const char *state;
+
+  i = asprintf (&filename, "/proc/%lu/status", (unsigned long) process);
+  assert (i > 0);
+
+  i = clock_gettime (CLOCK_MONOTONIC, &start);
+  assert (i == 0);
+
+  do
+    {
+      state = proc_string (filename, "State:\t");
+
+      /* torvalds/linux-2.6.git 464763cf1c6df632dccc8f2f4c7e50163154a2c0
+	 has changed "T (tracing stop)" to "t (tracing stop)".  Make the GDB
+	 testcase backward compatible with older Linux kernels.  */
+      if (strcmp (state, "T (tracing stop)") == 0)
+	state = "t (tracing stop)";
+
+      if (strcmp (state, wanted) == 0)
+	{
+	  free (filename);
+	  return;
+	}
+
+      if (sched_yield ())
+	{
+	  perror ("sched_yield()");
+	  exit (EXIT_FAILURE);
+	}
+
+      i = clock_gettime (CLOCK_MONOTONIC, &now);
+      assert (i == 0);
+      assert (now.tv_sec >= start.tv_sec);
+    }
+  while (now.tv_sec - start.tv_sec < TIMEOUT);
+
+  fprintf (stderr, "Timed out waiting for PID %lu \"%s\" (now it is \"%s\")!\n",
+	   (unsigned long) process, wanted, state);
+  exit (EXIT_FAILURE);
+}
+
+static volatile pid_t tracer = 0;
+static pthread_t thread1, thread2;
+
+static void
+cleanup (void)
+{
+  printf ("Resuming GDB PID %lu.\n", (unsigned long) tracer);
+
+  if (tracer)
+    {
+      int i;
+      int tracer_save = tracer;
+
+      tracer = 0;
+
+      i = kill (tracer_save, SIGCONT);
+      assert (i == 0);
+    }
+}
+
+int
+main (int argc, char **argv)
+{
+  int i;
+  int standalone = 0;
+  struct sigaction act;
+
+  if (argc == 2 && strcmp (argv[1], "-s") == 0)
+    standalone = 1;
+  else
+    assert (argc == 1);
+
+  setbuf (stdout, NULL);
+
+  timed_mutex_lock (&thread1_tid_mutex);
+  timed_mutex_lock (&thread2_tid_mutex);
+
+  timed_mutex_lock (&terminate_mutex);
+
+  errno = 0;
+  memset (&act, 0, sizeof (act));
+  act.sa_sigaction = handler;
+  act.sa_flags = SA_RESTART | SA_SIGINFO;
+  i = sigemptyset (&act.sa_mask);
+  assert_perror (errno);
+  assert (i == 0);
+  i = sigaction (SIGUSR1, &act, NULL);
+  assert_perror (errno);
+  assert (i == 0);
+  i = sigaction (SIGUSR2, &act, NULL);
+  assert_perror (errno);
+  assert (i == 0);
+
+  i = pthread_create (&thread1, NULL, thread1_func, NULL);
+  assert (i == 0);
+
+  i = pthread_create (&thread2, NULL, thread2_func, NULL);
+  assert (i == 0);
+
+  if (!standalone)
+    {
+      tracer = proc_ulong ("/proc/self/status", "TracerPid:\t");
+      if (tracer == 0)
+	{
+	  fprintf (stderr, "The testcase must be run by GDB!\n");
+	  exit (EXIT_FAILURE);
+	}
+      if (tracer != getppid ())
+	{
+	  fprintf (stderr, "The testcase parent must be our GDB tracer!\n");
+	  exit (EXIT_FAILURE);
+	}
+    }
+
+  /* SIGCONT our debugger in the case of our crash as we would deadlock
+     otherwise.  */
+
+  atexit (cleanup);
+
+  printf ("Stopping GDB PID %lu.\n", (unsigned long) tracer);
+
+  if (tracer)
+    {
+      i = kill (tracer, SIGSTOP);
+      assert (i == 0);
+      state_wait (tracer, "T (stopped)");
+    }
+
+  /* Threads are now waiting at timed_mutex_lock (thread1_tid_mutex)
+     and so they could not trigger the signals before GDB is unstopped
+     later.  Threads get resumed by the pthread_cond_wait below.  Use
+     `while' loops for protection against spurious pthread_cond_wait
+     wakeups.  */
+
+  printf ("Waiting till the threads initialize their TIDs.\n");
+
+  while (thread1_tid == 0)
+    {
+      i = pthread_cond_wait (&thread1_tid_cond, &thread1_tid_mutex);
+      assert (i == 0);
+    }
+
+  while (thread2_tid == 0)
+    {
+      i = pthread_cond_wait (&thread2_tid_cond, &thread2_tid_mutex);
+      assert (i == 0);
+    }
+
+  printf ("Thread 1 TID = %lu, thread 2 TID = %lu, PID = %lu.\n",
+	  (unsigned long) thread1_tid, (unsigned long) thread2_tid,
+	  (unsigned long) getpid ());
+
+  errno = 0;
+  i = tgkill (getpid (), thread1_tid, SIGUSR1);
+  assert_perror (errno);
+  assert (i == 0);
+  i = tgkill (getpid (), thread1_tid, SIGUSR2);
+  assert_perror (errno);
+  assert (i == 0);
+  i = tgkill (getpid (), thread2_tid, SIGUSR1);
+  assert_perror (errno);
+  assert (i == 0);
+  i = tgkill (getpid (), thread2_tid, SIGUSR2);
+  assert_perror (errno);
+  assert (i == 0);
+
+  printf ("Waiting till the threads are trapped by the signals.\n");
+
+  if (tracer)
+    {
+      /* s390x-unknown-linux-gnu will fail with "R (running)".  */
+
+      state_wait (thread1_tid, "t (tracing stop)");
+
+      state_wait (thread2_tid, "t (tracing stop)");
+    }
+
+  cleanup ();
+
+  printf ("Joining the threads.\n");
+
+  i = pthread_mutex_unlock (&terminate_mutex);
+  assert (i == 0);
+
+  i = pthread_join (thread1, NULL);
+  assert (i == 0);
+
+  i = pthread_join (thread2, NULL);
+  assert (i == 0);
+
+  printf ("Exiting.\n");	/* break-at-exit */
+
+  return EXIT_SUCCESS;
+}
diff --git a/gdb/testsuite/gdb.threads/siginfo-threads.exp b/gdb/testsuite/gdb.threads/siginfo-threads.exp
new file mode 100644
index 0000000..f3f9c51
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/siginfo-threads.exp
@@ -0,0 +1,99 @@
+# Copyright 2010-2012 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/>.
+
+standard_testfile
+set executable ${testfile}
+
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" \
+	 ${binfile} \
+	 executable \
+	 [list debug additional_flags=-lrt]] != "" } {
+    return -1
+}
+
+clean_restart $testfile
+
+if ![runto_main] {
+    return -1
+}
+
+# `nostop noprint pass' could in some cases report false PASS due to
+# the (preempt 'handle') code path in linux-nat.c.
+
+gdb_test "handle SIGUSR1 stop print pass" \
+    "Signal\[ \t\]+Stop\[ \t\]+Print\[ \t\]+Pass to program\[ \t\]+Description\r\nSIGUSR1\[ \t\]+Yes\[ \t\]+Yes\[ \t\]+Yes\[ \t\].*"
+gdb_test "handle SIGUSR2 stop print pass" \
+    "Signal\[ \t\]+Stop\[ \t\]+Print\[ \t\]+Pass to program\[ \t\]+Description\r\nSIGUSR2\[ \t\]+Yes\[ \t\]+Yes\[ \t\]+Yes\[ \t\].*"
+
+gdb_breakpoint [gdb_get_line_number "break-at-exit"]
+
+set test "get pid"
+gdb_test_multiple "p getpid ()" $test {
+    -re " = (\[0-9\]+)\r\n$gdb_prompt $" {
+	set pid $expect_out(1,string)
+	pass $test
+    }
+}
+
+for {set sigcount 0} {$sigcount < 4} {incr sigcount} {
+    set test "catch signal $sigcount"
+    set sigusr ""
+    gdb_test_multiple "continue" $test {
+	-re "Program received signal SIGUSR(\[12\]), User defined signal \[12\]\\.\r\n.*\r\n$gdb_prompt $" {
+	    set sigusr $expect_out(1,string)
+	    pass $test
+	}
+    }
+    if {$sigusr == ""} {
+	return -1
+    }
+
+    set test "signal $sigcount si_signo"
+    if {$sigusr == 1} {
+	set signo 10
+    } else {
+	set signo 12
+    }
+    gdb_test_multiple {p $_siginfo.si_signo} $test {
+	-re " = $signo\r\n$gdb_prompt $" {
+	    pass $test
+	}
+	-re "Attempt to extract a component of a value that is not a structure\\.\r\n$gdb_prompt $" {
+	    unsupported $test
+	}
+    }
+
+    set test "signal $sigcount si_code is SI_TKILL"
+    gdb_test_multiple {p $_siginfo.si_code} $test {
+	-re " = -6\r\n$gdb_prompt $" {
+	    pass $test
+	}
+	-re "Attempt to extract a component of a value that is not a structure\\.\r\n$gdb_prompt $" {
+	    unsupported $test
+	}
+    }
+
+    set test "signal $sigcount si_pid"
+    gdb_test_multiple {p $_siginfo._sifields._kill.si_pid} $test {
+	-re " = $pid\r\n$gdb_prompt $" {
+	    pass $test
+	}
+	-re "Attempt to extract a component of a value that is not a structure\\.\r\n$gdb_prompt $" {
+	    unsupported $test
+	}
+    }
+}
+
+gdb_continue_to_breakpoint break-at-exit ".*break-at-exit.*"
diff --git a/gdb/testsuite/gdb.threads/sigstep-threads.c b/gdb/testsuite/gdb.threads/sigstep-threads.c
new file mode 100644
index 0000000..ca77fe4
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/sigstep-threads.c
@@ -0,0 +1,54 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2010-2012 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 <pthread.h>
+#include <assert.h>
+#include <signal.h>
+
+#include <asm/unistd.h>
+#include <unistd.h>
+#define tgkill(tgid, tid, sig) syscall (__NR_tgkill, (tgid), (tid), (sig))
+#define gettid() syscall (__NR_gettid)
+
+static volatile int var;
+
+static void
+handler (int signo)	/* step-0 */
+{			/* step-0 */
+  var++;		/* step-1 */
+  tgkill (getpid (), gettid (), SIGUSR1);	/* step-2 */
+}
+
+static void *
+start (void *arg)
+{
+  tgkill (getpid (), gettid (), SIGUSR1);
+  assert (0);
+  return NULL;
+}
+
+int
+main (void)
+{
+  pthread_t thread;
+
+  signal (SIGUSR1, handler);
+
+  pthread_create (&thread, NULL, start, NULL);
+  start (NULL);	/* main-start */
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.threads/sigstep-threads.exp b/gdb/testsuite/gdb.threads/sigstep-threads.exp
new file mode 100644
index 0000000..484ca37
--- /dev/null
+++ b/gdb/testsuite/gdb.threads/sigstep-threads.exp
@@ -0,0 +1,73 @@
+# Copyright 2010-2012 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/>.
+
+standard_testfile
+set executable ${testfile}
+
+if { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
+    untested ${testfile}.exp
+    return -1
+}
+
+clean_restart $executable
+
+if ![runto_main] {
+    return -1;
+}
+
+# `noprint' would not test the full logic of GDB.
+gdb_test "handle SIGUSR1 nostop print pass" \
+    "\r\nSIGUSR1\[ \t\]+No\[ \t\]+Yes\[ \t\]+Yes\[ \t\].*"
+
+gdb_test_no_output "set scheduler-locking off"
+
+gdb_breakpoint [gdb_get_line_number "step-1"]
+gdb_test_no_output {set $step1=$bpnum}
+gdb_continue_to_breakpoint "step-1" ".* step-1 .*"
+gdb_test_no_output {disable $step1}
+
+# 1 as we are now stopped at the `step-1' label.
+set step_at 1
+for {set i 0} {$i < 100} {incr i} {
+    set test "step $i"
+    # Presume this step failed - as in the case of a timeout.
+    set failed 1
+    gdb_test_multiple "step" $test {
+	-re "\r\nProgram received signal SIGUSR1, User defined signal 1.\r\n" {
+	    exp_continue -continue_timer
+	}
+	-re "step-(\[012\]).*\r\n$gdb_prompt $" {
+	    set now $expect_out(1,string)
+	    if {$step_at == 2 && $now == 1} {
+		set failed 0
+	    } elseif {$step_at == 1 && $now == 2} {
+		set failed 0
+		# Continue over the re-signalling back to the handle entry.
+		gdb_test_no_output {enable $step1} ""
+		gdb_test "continue" " step-1 .*" ""
+		set now 1
+		gdb_test_no_output {disable $step1} ""
+	    } else  {
+		fail $test
+	    }
+	    set step_at $now
+	}
+    }
+    if $failed {
+	return
+    }
+}
+# We can never reliably say the racy problematic case has been tested.
+pass "step"