Re: [PATCH 27/31] Testcases for stepping over thread exit syscall (PR gdb/27338)

[Andrew Burgess <aburgess@redhat.com>]

Pedro Alves <pedro@palves.net> writes:

> From: Simon Marchi <simon.marchi@efficios.com>
>
> - New in this series version:
>
>  - gdb.threads/step-over-thread-exit.exp has a couple new testing axes:
>
>    - non-stop vs all-stop.
>
>    - in non-stop have the testcase explicitly stop all threads in
>      non-stop mode, vs not doing that.
>
>  - bail out of gdb.threads/step-over-thread-exit.exp early on FAIL, to
>    avoid cascading timeouts.
>
> Add new gdb.threads/step-over-thread-exit.exp and
> gdb.threads/step-over-thread-exit-while-stop-all-threads.exp
> testcases, exercising stepping over thread exit syscall.  These make
> use of lib/my-syscalls.S to define the exit syscall.

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>
> Co-authored-by: Pedro Alves <pedro@palves.net>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338
> Change-Id: Ie8b2c5747db99b7023463a897a8390d9e814a9c9
> ---
>  ...-over-thread-exit-while-stop-all-threads.c |  77 +++++++++++
>  ...ver-thread-exit-while-stop-all-threads.exp |  69 ++++++++++
>  .../gdb.threads/step-over-thread-exit.c       |  52 ++++++++
>  .../gdb.threads/step-over-thread-exit.exp     | 126 ++++++++++++++++++
>  gdb/testsuite/lib/my-syscalls.S               |   4 +
>  gdb/testsuite/lib/my-syscalls.h               |   5 +
>  6 files changed, 333 insertions(+)
>  create mode 100644 gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.c
>  create mode 100644 gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.exp
>  create mode 100644 gdb/testsuite/gdb.threads/step-over-thread-exit.c
>  create mode 100644 gdb/testsuite/gdb.threads/step-over-thread-exit.exp
>
> diff --git a/gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.c b/gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.c
> new file mode 100644
> index 00000000000..2699ad5d714
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.c
> @@ -0,0 +1,77 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2021-2022 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 "../lib/my-syscalls.h"
> +
> +#define NUM_THREADS 32
> +
> +static void *
> +stepper_over_exit_thread (void *v)
> +{
> +  my_exit (0);
> +
> +  /* my_exit above should exit the thread, we don't expect to reach
> +     here.  */
> +  abort ();
> +}
> +
> +static void *
> +spawner_thread (void *v)
> +{
> +  for (;;)
> +    {
> +      pthread_t threads[NUM_THREADS];
> +      int i;
> +
> +      for (i = 0; i < NUM_THREADS; i++)
> +	pthread_create (&threads[i], NULL, stepper_over_exit_thread, NULL);
> +
> +      for (i = 0; i < NUM_THREADS; i++)
> +	pthread_join (threads[i], NULL);
> +    }
> +}
> +
> +static void
> +break_here (void)
> +{
> +}
> +
> +static void *
> +breakpoint_hitter_thread (void *v)
> +{
> +  for (;;)
> +    break_here ();
> +}
> +
> +int
> +main ()
> +{
> +  pthread_t breakpoint_hitter;
> +  pthread_t spawner;
> +
> +  alarm (60);
> +
> +  pthread_create (&spawner, NULL, spawner_thread, NULL);
> +  pthread_create (&breakpoint_hitter, NULL, breakpoint_hitter_thread, NULL);
> +
> +  pthread_join (spawner, NULL);
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.exp b/gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.exp
> new file mode 100644
> index 00000000000..6a46aff700e
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/step-over-thread-exit-while-stop-all-threads.exp
> @@ -0,0 +1,69 @@
> +# Copyright 2021-2022 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 stepping over a breakpoint installed on an instruction that
> +# exits the thread, while another thread is repeatedly hitting a
> +# breakpoint, causing GDB to stop all threads.
> +
> +standard_testfile .c
> +
> +set syscalls_src $srcdir/lib/my-syscalls.S
> +
> +if { [build_executable "failed to prepare" $testfile \
> +	  [list $srcfile $syscalls_src] {debug pthreads}] == -1 } {
> +    return
> +}
> +
> +proc test {displaced-stepping target-non-stop} {
> +    save_vars ::GDBFLAGS {
> +	append ::GDBFLAGS " -ex \"maintenance set target-non-stop ${target-non-stop}\""
> +	clean_restart $::binfile
> +    }
> +
> +    gdb_test_no_output "set displaced-stepping ${displaced-stepping}"
> +
> +    if { ![runto_main] } {
> +	return
> +    }
> +
> +    # The "stepper over exit" threads will step over an instruction
> +    # that causes them to exit.
> +    gdb_test "break my_exit_syscall if 0"
> +
> +    # The "breakpoint hitter" thread will repeatedly hit this
> +    # breakpoint, causing GDB to stop all threads.
> +    gdb_test "break break_here"
> +
> +    # To avoid flooding the log with thread created/exited messages.
> +    gdb_test_no_output "set print thread-events off"
> +
> +    # Make sure the target reports the breakpoint stops.
> +    gdb_test_no_output "set breakpoint condition-evaluation host"
> +
> +    for { set i 0 } { $i < 30 } { incr i } {
> +	with_test_prefix "iter $i" {
> +	    if { [gdb_test "continue" "hit Breakpoint $::decimal, break_here .*"] != 0 } {
> +		# Exit if there's a failure to avoid lengthy timeouts.
> +		break
> +	    }
> +	}
> +    }
> +}
> +
> +foreach_with_prefix displaced-stepping {off auto} {
> +    foreach_with_prefix target-non-stop {off on} {
> +	test ${displaced-stepping} ${target-non-stop}
> +    }
> +}
> diff --git a/gdb/testsuite/gdb.threads/step-over-thread-exit.c b/gdb/testsuite/gdb.threads/step-over-thread-exit.c
> new file mode 100644
> index 00000000000..878e5924c5c
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/step-over-thread-exit.c
> @@ -0,0 +1,52 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2021-2022 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 <stdlib.h>
> +#include "../lib/my-syscalls.h"
> +
> +static void *
> +thread_func (void *arg)
> +{
> +  my_exit (0);
> +
> +  /* my_exit above should exit the thread, we don't expect to reach
> +     here.  */
> +  abort ();
> +}
> +
> +int
> +main (void)
> +{
> +  int i;
> +
> +  /* Spawn and join a thread, 100 times.  */
> +  for (i = 0; i < 100; i++)
> +    {
> +      pthread_t thread;
> +      int ret;
> +
> +      ret = pthread_create (&thread, NULL, thread_func, NULL);
> +      assert (ret == 0);
> +
> +      ret = pthread_join (thread, NULL);
> +      assert (ret == 0);
> +    }
> +
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.threads/step-over-thread-exit.exp b/gdb/testsuite/gdb.threads/step-over-thread-exit.exp
> new file mode 100644
> index 00000000000..ed8534cf518
> --- /dev/null
> +++ b/gdb/testsuite/gdb.threads/step-over-thread-exit.exp
> @@ -0,0 +1,126 @@
> +# Copyright 2021-2022 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 stepping over a breakpoint installed on an instruction that
> +# exits the thread.
> +
> +standard_testfile .c
> +
> +set syscalls_src $srcdir/lib/my-syscalls.S
> +
> +if { [build_executable "failed to prepare" $testfile \
> +	  [list $srcfile $syscalls_src] {debug pthreads}] == -1 } {
> +    return
> +}
> +
> +# Each argument is a different testing axis, most of them obvious.
> +# NS_STOP_ALL is only used if testing "set non-stop on", and indicates
> +# whether to have GDB explicitly stop all threads before continuing to
> +# thread exit.
> +proc test {displaced-stepping non-stop target-non-stop schedlock ns_stop_all} {
> +    if {${non-stop} == "off" && $ns_stop_all} {
> +	error "invalid arguments"
> +    }
> +
> +    save_vars ::GDBFLAGS {
> +	append ::GDBFLAGS " -ex \"maintenance set target-non-stop ${target-non-stop}\""
> +	append ::GDBFLAGS " -ex \"set non-stop ${non-stop}\""
> +	clean_restart $::binfile
> +    }
> +
> +    gdb_test_no_output "set displaced-stepping ${displaced-stepping}"
> +
> +    if { ![runto_main] } {
> +	return
> +    }
> +
> +    gdb_breakpoint "my_exit_syscall"
> +
> +    if {$schedlock
> +	|| (${non-stop} == "on" && $ns_stop_all)} {
> +	gdb_test "continue" \
> +	    "Thread 2 .*hit Breakpoint $::decimal.* my_exit_syscall .*" \
> +	    "continue until syscall"
> +
> +	if {${non-stop} == "on"} {
> +	    # The test only spawns one thread at a time, so this just
> +	    # stops the main thread.
> +	    gdb_test_multiple "interrupt -a" "" {
> +		-re "$::gdb_prompt " {
> +		    gdb_test_multiple "" $gdb_test_name {
> +			-re "Thread 1 \[^\r\n\]*stopped." {
> +			    pass $gdb_test_name
> +			}
> +		    }
> +		}
> +	    }
> +	}
> +
> +	gdb_test "thread 2" "Switching to thread 2 .*"
> +
> +	gdb_test_no_output "set scheduler-locking ${schedlock}"
> +
> +	gdb_test "continue" \
> +	    "No unwaited-for children left." \
> +	    "continue stops when thread exits"
> +    } else {
> +	gdb_test_no_output "set scheduler-locking ${schedlock}"
> +
> +	for { set i 0 } { $i < 100 } { incr i } {
> +	    with_test_prefix "iter $i" {
> +		set ok 0
> +		set thread "<unknown>"
> +		gdb_test_multiple "continue" "" {
> +		    -re -wrap "Thread ($::decimal) .*hit Breakpoint $::decimal.* my_exit_syscall .*" {
> +			set thread $expect_out(1,string)
> +			set ok 1
> +		    }
> +		}
> +		if {!${ok}} {
> +		    # Exit if there's a failure to avoid lengthy
> +		    # timeouts.
> +		    break
> +		}
> +
> +		if {${non-stop}} {
> +		    gdb_test "thread $thread" "Switching to thread .*" \
> +			"switch to event thread"
> +		}
> +	    }
> +	}
> +    }
> +}
> +
> +foreach_with_prefix displaced-stepping {off auto} {
> +    foreach_with_prefix non-stop {off on} {
> +	foreach_with_prefix target-non-stop {off on} {
> +	    if {${non-stop} == "on" && ${target-non-stop} == "off"} {
> +		# Invalid combination.
> +		continue
> +	    }
> +
> +	    foreach_with_prefix schedlock {off on} {
> +		if {${non-stop} == "on"} {
> +		    foreach_with_prefix ns_stop_all {0 1} {
> +			test ${displaced-stepping} ${non-stop} ${target-non-stop} \
> +			    ${schedlock} ${ns_stop_all}
> +		    }
> +		} else {
> +		    test ${displaced-stepping} ${non-stop} ${target-non-stop} ${schedlock} 0
> +		}
> +	    }
> +	}
> +    }
> +}
> diff --git a/gdb/testsuite/lib/my-syscalls.S b/gdb/testsuite/lib/my-syscalls.S
> index 6fb53624f31..ff62b5eb4e9 100644
> --- a/gdb/testsuite/lib/my-syscalls.S
> +++ b/gdb/testsuite/lib/my-syscalls.S
> @@ -69,4 +69,8 @@ NAME ## _syscall:		;\
>  
>  SYSCALL (my_execve, __NR_execve)
>  
> +/* void my_exit (int code);  */
> +
> +SYSCALL (my_exit, __NR_exit)
> +
>  	.section	.note.GNU-stack,"",@progbits
> diff --git a/gdb/testsuite/lib/my-syscalls.h b/gdb/testsuite/lib/my-syscalls.h
> index a0c069c58e5..ceaa587b3e6 100644
> --- a/gdb/testsuite/lib/my-syscalls.h
> +++ b/gdb/testsuite/lib/my-syscalls.h
> @@ -22,4 +22,9 @@
>  
>  int my_execve (const char *file, char *argv[], char *envp[]);
>  
> +/* `exit` syscall, which makes the thread exit (as opposed to
> +   `exit_group`, which makes the process exit).  */
> +
> +void my_exit (int code);
> +
>  #endif /* MY_SYSCALLS_H */
> -- 
> 2.36.0