Re: [patch 3/4] Fix hw watchpoints #2: reordered / simultaneously hit

Pedro Alves
2009-11-20T16:58:36Z

On Wednesday 18 November 2009 10:08:10, Jan Kratochvil wrote:

> @@ -5368,6 +5420,8 @@ linux_nat_add_target (struct target_ops *t)
> t->to_pid_to_str = linux_nat_pid_to_str;
> t->to_has_thread_control = tc_schedlock;
> t->to_thread_address_space = linux_nat_thread_address_space;
> + if (linux_ops->to_stopped_data_address)
> + t->to_stopped_data_address = linux_nat_stopped_data_address;

We were talking on IRC about this ..

> --- a/gdb/i386-nat.c
> +++ b/gdb/i386-nat.c
> @@ -585,7 +585,7 @@ static int
> i386_stopped_by_watchpoint (void)
> {
> CORE_ADDR addr = 0;
> - return i386_stopped_data_address (&current_target, &addr);
> + return target_stopped_data_address (&current_target, &addr);
> }

.. and this changes, which didn't look that clean, because they mix
up the single-threaded layer linux_ops, the thread agnostic i386-nat.c
and the multi-lwp layer (linux-nat.c).

Here's the alternative I was talking about. Have linux_ops worry
about extracting stopped_by_watchpoint/stopped_data_address
from the inferior, either by reading debug regs, or from the
siginfo, and have linux_nat.c always return what's cached in
the lwp structure.

I've also rewritten the comments around save_sigtrap.

WDYT?

--
Pedro Alves

gdb/
2009-11-20 Jan Kratochvil <jan.kratochvil@redhat.com>
Pedro Alves <pedro@codesourcery.com>

Fix reordered watchpoints triggered in other threads during all-stop.

* linux-nat.c (resume_callback, linux_nat_resume): Clear
stopped_by_watchpoint_p.
(save_sigtrap, linux_nat_stopped_by_watchpoint)
(linux_nat_stopped_data_address): New.
(stop_wait_callback, linux_nat_filter_event): Call save_sigtrap.
(linux_nat_add_target): Install linux_nat_stopped_by_watchpoint
and linux_nat_stopped_data_address.
* linux-nat.h (struct lwp_info): New fields stopped_by_watchpoint,
stopped_data_address_p and stopped_data_address.

gdb/testsuite/
2009-11-20 Jan Kratochvil <jan.kratochvil@redhat.com>

* gdb.base/watchthreads-reorder.exp,
gdb.base/watchthreads-reorder.c: New.

---
gdb/linux-nat.c | 83 ++++
gdb/linux-nat.h | 13
gdb/testsuite/gdb.threads/watchthreads-reorder.c | 369 +++++++++++++++++++++
gdb/testsuite/gdb.threads/watchthreads-reorder.exp | 103 +++++
4 files changed, 566 insertions(+), 2 deletions(-)

Index: src/gdb/linux-nat.c
===================================================================
--- src.orig/gdb/linux-nat.c 2009-11-20 16:54:06.000000000 +0000
+++ src/gdb/linux-nat.c 2009-11-20 16:54:13.000000000 +0000
@@ -1882,6 +1882,7 @@ resume_callback (struct lwp_info *lp, vo
lp->stopped = 0;
lp->step = 0;
memset (&lp->siginfo, 0, sizeof (lp->siginfo));
+ lp->stopped_by_watchpoint_p = 0;
}
else if (lp->stopped && debug_linux_nat)
fprintf_unfiltered (gdb_stdlog, "RC: Not resuming sibling %s (has pending)\n",
@@ -2019,6 +2020,7 @@ linux_nat_resume (struct target_ops *ops

linux_ops->to_resume (linux_ops, ptid, step, signo);
memset (&lp->siginfo, 0, sizeof (lp->siginfo));
+ lp->stopped_by_watchpoint_p = 0;

if (debug_linux_nat)
fprintf_unfiltered (gdb_stdlog,
@@ -2570,6 +2572,75 @@ maybe_clear_ignore_sigint (struct lwp_in
}
}

+/* Fetch the possible triggered data watchpoint info and store it in
+ LP.
+
+ On some archs, like x86, that use debug registers to set
+ watchpoints, it's possible that the way to know which watched
+ address trapped, is to check the register that is used to select
+ which address to watch. Problem is, between setting the watchpoint
+ and reading back which data address trapped, the user may change
+ the set of watchpoints, and, as a consequence, GDB changes the
+ debug registers in the inferior. To avoid reading back a stale
+ stopped-data-address when that happens, we cache in LP the fact
+ that a watchpoint trapped, and the corresponding data address, as
+ soon as we see LP stop with a SIGTRAP. If GDB changes the debug
+ registers meanwhile, we have the cached data we can rely on. */
+
+static void
+save_sigtrap (struct lwp_info *lp)
+{
+ struct cleanup *old_chain;
+
+ if (linux_ops->to_stopped_by_watchpoint == NULL)
+ {
+ lp->stopped_by_watchpoint_p = 0;
+ return;
+ }
+
+ if (linux_ops->to_stopped_data_address == NULL)
+ {
+ lp->stopped_data_address_p = 0;
+ return;
+ }
+
+ old_chain = save_inferior_ptid ();
+ inferior_ptid = lp->ptid;
+
+ lp->stopped_by_watchpoint_p = linux_ops->to_stopped_by_watchpoint ();
+
+ if (lp->stopped_by_watchpoint_p)
+ lp->stopped_data_address_p =
+ linux_ops->to_stopped_data_address (&current_target,
+ &lp->stopped_data_address);
+
+ do_cleanups (old_chain);
+}
+
+/* See save_sigtrap. */
+
+static int
+linux_nat_stopped_by_watchpoint (void)
+{
+ struct lwp_info *lp = find_lwp_pid (inferior_ptid);
+
+ gdb_assert (lp != NULL);
+
+ return lp->stopped_by_watchpoint_p;
+}
+
+static int
+linux_nat_stopped_data_address (struct target_ops *ops, CORE_ADDR *addr_p)
+{
+ struct lwp_info *lp = find_lwp_pid (inferior_ptid);
+
+ gdb_assert (lp != NULL);
+
+ *addr_p = lp->stopped_data_address;
+
+ return lp->stopped_data_address_p;
+}
+
/* Wait until LP is stopped. */

static int
@@ -2628,6 +2699,8 @@ stop_wait_callback (struct lwp_info *lp,
/* Save the trap's siginfo in case we need it later. */
save_siginfo (lp);

+ save_sigtrap (lp);
+
/* Now resume this LWP and get the SIGSTOP event. */
errno = 0;
ptrace (PTRACE_CONT, GET_LWP (lp->ptid), 0, 0);
@@ -3027,9 +3100,13 @@ linux_nat_filter_event (int lwpid, int s
return NULL;
}

- /* Save the trap's siginfo in case we need it later. */
if (WIFSTOPPED (status) && WSTOPSIG (status) == SIGTRAP)
- save_siginfo (lp);
+ {
+ /* Save the trap's siginfo in case we need it later. */
+ save_siginfo (lp);
+
+ save_sigtrap (lp);
+ }

/* Check if the thread has exited. */
if ((WIFEXITED (status) || WIFSIGNALED (status))
@@ -5368,6 +5445,8 @@ linux_nat_add_target (struct target_ops
t->to_pid_to_str = linux_nat_pid_to_str;
t->to_has_thread_control = tc_schedlock;
t->to_thread_address_space = linux_nat_thread_address_space;
+ t->to_stopped_by_watchpoint = linux_nat_stopped_by_watchpoint;
+ t->to_stopped_data_address = linux_nat_stopped_data_address;

t->to_can_async_p = linux_nat_can_async_p;
t->to_is_async_p = linux_nat_is_async_p;
Index: src/gdb/linux-nat.h
===================================================================
--- src.orig/gdb/linux-nat.h 2009-11-20 16:54:06.000000000 +0000
+++ src/gdb/linux-nat.h 2009-11-20 16:54:40.000000000 +0000
@@ -62,6 +62,19 @@ struct lwp_info
be the address of a hardware watchpoint. */
struct siginfo siginfo;

+ /* STOPPED_BY_WATCHPOINT is non-zero if this LWP stopped with a data
+ watchpoint trap. In such case STOPPED_DATA_ADDRESS contains data
+ address of the triggered data watchpoint. */
+ int stopped_by_watchpoint_p;
+
+ /* On architectures where it is possible to know the data address of
+ a triggered watchpoint, STOPPED_DATA_ADDRESS_P is non-zero, and
+ STOPPED_DATA_ADDRESS contains such the data address. Otherwise,
+ STOPPED_DATA_ADDRESS_P is false, and STOPPED_DATA_ADDRESS is
+ undefined. Only valid if STOPPED_BY_WATCHPOINT_P is true. */
+ int stopped_data_address_p;
+ CORE_ADDR stopped_data_address;
+
/* Non-zero if we expect a duplicated SIGINT. */
int ignore_sigint;

Index: src/gdb/testsuite/gdb.threads/watchthreads-reorder.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ src/gdb/testsuite/gdb.threads/watchthreads-reorder.c 2009-11-20 16:54:13.000000000 +0000
@@ -0,0 +1,369 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2009 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)
+
+/* Terminate always in the main task, it can lock up with SIGSTOPped GDB
+ otherwise. */
+#define TIMEOUT (gettid () == getpid() ? 10 : 15)
+
+static pthread_mutex_t gdbstop_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
+
+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 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 pthread_mutex_t terminate_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
+
+/* These variables must have lower in-memory addresses than thread1_rwatch and
+ thread2_rwatch so that they take their watchpoint slots. */
+
+static int unused1_rwatch;
+static int unused2_rwatch;
+
+static volatile int thread1_rwatch;
+static volatile int thread2_rwatch;
+
+/* Do not use alarm as it would create a ptrace event which would hang up us 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 *
+thread1_func (void *unused)
+{
+ int i;
+ volatile int rwatch_store;
+
+ thread1_tid = gettid ();
+ i = pthread_cond_signal (&thread1_tid_cond);
+ assert (i == 0);
+
+ /* Be sure GDB is already stopped before continuing. */
+ timed_mutex_lock (&gdbstop_mutex);
+ i = pthread_mutex_unlock (&gdbstop_mutex);
+ assert (i == 0);
+
+ rwatch_store = thread1_rwatch;
+
+ /* 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);
+
+ return NULL;
+}
+
+static void *
+thread2_func (void *unused)
+{
+ int i;
+ volatile int rwatch_store;
+
+ thread2_tid = gettid ();
+ i = pthread_cond_signal (&thread2_tid_cond);
+ assert (i == 0);
+
+ /* Be sure GDB is already stopped before continuing. */
+ timed_mutex_lock (&gdbstop_mutex);
+ i = pthread_mutex_unlock (&gdbstop_mutex);
+ assert (i == 0);
+
+ rwatch_store = thread2_rwatch;
+
+ /* 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);
+
+ 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");
+ 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;
+
+ if (argc == 2 && strcmp (argv[1], "-s") == 0)
+ standalone = 1;
+ else
+ assert (argc == 1);
+
+ setbuf (stdout, NULL);
+
+ timed_mutex_lock (&gdbstop_mutex);
+
+ timed_mutex_lock (&terminate_mutex);
+
+ 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)");
+ }
+
+ timed_mutex_lock (&thread1_tid_mutex);
+ timed_mutex_lock (&thread2_tid_mutex);
+
+ /* Let the threads start. */
+ i = pthread_mutex_unlock (&gdbstop_mutex);
+ assert (i == 0);
+
+ printf ("Waiting till the threads initialize their TIDs.\n");
+
+ if (thread1_tid == 0)
+ {
+ i = pthread_cond_wait (&thread1_tid_cond, &thread1_tid_mutex);
+ assert (i == 0);
+
+ assert (thread1_tid > 0);
+ }
+
+ if (thread2_tid == 0)
+ {
+ i = pthread_cond_wait (&thread2_tid_cond, &thread2_tid_mutex);
+ assert (i == 0);
+
+ assert (thread2_tid > 0);
+ }
+
+ printf ("Thread 1 TID = %lu, thread 2 TID = %lu, PID = %lu.\n",
+ (unsigned long) thread1_tid, (unsigned long) thread2_tid,
+ (unsigned long) getpid ());
+
+ printf ("Waiting till the threads get trapped by the watchpoints.\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 */
+
+ /* Just prevent compiler `warning: unusedX_rwatch defined but not used'. */
+ unused1_rwatch = 1;
+ unused2_rwatch = 2;
+
+ return EXIT_SUCCESS;
+}
Index: src/gdb/testsuite/gdb.threads/watchthreads-reorder.exp
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ src/gdb/testsuite/gdb.threads/watchthreads-reorder.exp 2009-11-20 16:54:13.000000000 +0000
@@ -0,0 +1,103 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2009 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 GDB can cope with two watchpoints being hit by different threads at the
+# same time, GDB reports one of them and after "continue" to report the other
+# one GDB should not be confused by differently set watchpoints that time.
+# This is the goal of "reorder1". "reorder0" tests the basic functionality of
+# two watchpoints being hit at the same time, without reordering them during the
+# stop. The formerly broken functionality is due to the all-stop mode default
+# "show breakpoint always-inserted" being "off". Formerly the remembered hit
+# could be assigned during continuation of a thread with pending SIGTRAP to the
+# different/new watchpoint, just based on the watchpoint/debug register number.
+
+if {(![istarget "i?86-*-*"] && ![istarget "x86_64-*-*"]
+ && ![istarget "ia64-*-*"] && ![istarget "s390*-*-*"])
+ || [target_info exists gdb,no_hardware_watchpoints]
+ || ![istarget *-*-linux*]} {
+ return 0
+}
+
+set testfile "watchthreads-reorder"
+set srcfile ${testfile}.c
+set binfile ${objdir}/${subdir}/${testfile}
+if {[gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" ${binfile} executable [list debug additional_flags=-lrt]] != "" } {
+ return -1
+}
+
+foreach reorder {0 1} {
+
+ global pf_prefix
+ set prefix_test $pf_prefix
+ lappend pf_prefix "reorder$reorder:"
+
+ clean_restart $testfile
+
+ gdb_test "set can-use-hw-watchpoints 1"
+
+ if ![runto_main] {
+ return -1
+ }
+
+ # Use "rwatch" as "watch" would report the watchpoint changed just based on its
+ # read memory value during a stop by unrelated event. We are interested in not
+ # losing the hardware watchpoint trigger.
+
+ gdb_test "rwatch thread1_rwatch" "Hardware read watchpoint \[0-9\]+: thread1_rwatch"
+ set test "rwatch thread2_rwatch"
+ gdb_test_multiple $test $test {
+ -re "Target does not support this type of hardware watchpoint\\.\r\n$gdb_prompt $" {
+ # ppc64 supports at most 1 hw watchpoints.
+ unsupported $test
+ return
+ }
+ -re "Hardware read watchpoint \[0-9\]+: thread2_rwatch\r\n$gdb_prompt $" {
+ pass $test
+ }
+ }
+ gdb_breakpoint [gdb_get_line_number "break-at-exit"]
+
+ # The watchpoints can happen in arbitrary order depending on random:
+ # SEL: Found 2 SIGTRAP events, selecting #[01]
+ # As GDB contains no srand() on the specific host/OS it will behave always the
+ # same. Such order cannot be guaranteed for GDB in general.
+
+ gdb_test "continue" \
+ "Hardware read watchpoint \[0-9\]+: thread\[12\]_rwatch\r\n\r\nValue = 0\r\n0x\[0-9a-f\]+ in thread\[12\]_func .*" \
+ "continue a"
+
+ if $reorder {
+ # GDB orders watchpoints by their addresses so inserting new variables
+ # with lower addresses will shift the former watchpoints to higher
+ # debug registers.
+
+ gdb_test "rwatch unused1_rwatch" "Hardware read watchpoint \[0-9\]+: unused1_rwatch"
+ gdb_test "rwatch unused2_rwatch" "Hardware read watchpoint \[0-9\]+: unused2_rwatch"
+ }
+
+ gdb_test "continue" \
+ "Hardware read watchpoint \[0-9\]+: thread\[12\]_rwatch\r\n\r\nValue = 0\r\n0x\[0-9a-f\]+ in thread\[12\]_func .*" \
+ "continue b"
+
+ # While the debug output itself is not checked in this testcase one bug was
+ # found in the DEBUG_INFRUN code path.
+ gdb_test "set debug infrun 1"
+
+ gdb_continue_to_breakpoint "break-at-exit" ".*break-at-exit.*"
+
+ set pf_prefix $prefix_test
+}