Testcases for stepping over thread exit syscall (PR gdb/27338)

- 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.

Co-authored-by: Pedro Alves <pedro@palves.net>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338
Change-Id: Ie8b2c5747db99b7023463a897a8390d9e814a9c9

6 files changed, 333 insertions, 0 deletions

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 */