binutils-gdb/gdb/testsuite/gdb.mi/mi-cmd-user-context.c

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gdb/testsuite: fix intermittent failures in gdb.mi/mi-cmd-user-context.exp I got failures like this once on a CI: frame^M &"frame\n"^M ~"#0 child_sub_function () at /home/jenkins/workspace/binutils-gdb_master_build/arch/amd64/target_board/unix/src/binutils-gdb/gdb/testsuite/gdb.mi/user-selected-context-sync.c:33\n"^M ~"33\t dummy = !dummy; /* thread loop line */\n"^M ^done^M (gdb) ^M FAIL: gdb.mi/mi-cmd-user-context.exp: frame 1 (unexpected output) The problem is that the test expects the following regexp: ".*#0 0x.*" And that typically works, when the output of the frame command looks like: #0 0x00005555555551bb in child_sub_function () at ... Note the lack of hexadecimal address in the failing case. Whether or not the hexadecimal address is printed (roughly) depends on whether the current PC is at the beginning of a line. So depending on where thread 2 was when GDB stopped it (after thread 1 hit its breakpoint), we can get either output. Adjust the regexps to not expect an hexadecimal prefix (0x) but a function name instead (either child_sub_function or child_function). That one is always printed, and is also a good check that we are in the frame we expect. Note that for test "frame 5", we are showing a pthread frame (on my system), so the function name is internal to pthread, not something we can rely on. In that case, it's almost certain that we are not at the beginning of a line, or that we don't have debug info, so I think it's fine to expect the hex prefix. And for test "frame 6", it's ok to _not_ expect a hex prefix (what the test currently does), since we are showing thread 1, which has hit a breakpoint placed at the beginning of a line. When testing this, Tom de Vries pointed out that the current test code doesn't ensure that the child threads are in child_sub_function when they are stopped. If the scheduler chooses so, it is possible for the child threads to be still in the pthread_barrier_wait or child_function functions when they get stopped. So that would be another racy failure waiting to happen. The only way I can think of to ensure the child threads are in the child_sub_function function when they get stopped is to synchronize the threads using some variables instead of pthread_barrier_wait. So, replace the barrier with an array of flags (one per child thread). Each child thread flips its flag in child_sub_function to allow the main thread to make progress and eventually hit the breakpoint. I copied user-selected-context-sync.c to a new mi-cmd-user-context.c and made modifications to that, to avoid interfering with user-selected-context-sync.exp. Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29025 Change-Id: I919673bbf9927158beb0e8b7e9e980b8d65eca90
2022-04-05 00:08:22 +08:00
/* This testcase is part of GDB, the GNU debugger.
Copyright 2016-2022 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 <unistd.h>
#include <stdint.h>
#define NUM_THREADS 2
static volatile int unblock_main[NUM_THREADS];
static void
child_sub_function (int child_idx)
{
volatile int dummy = 0;
unblock_main[child_idx] = 1;
while (1)
/* Dummy loop body to allow setting breakpoint. */
dummy = !dummy; /* thread loop line */
}
static void *
child_function (void *args)
{
int child_idx = (int) (uintptr_t) args;
child_sub_function (child_idx); /* thread caller line */
return NULL;
}
int
main (void)
{
int i = 0;
pthread_t threads[NUM_THREADS];
/* Make the test exit eventually. */
alarm (20);
for (i = 0; i < NUM_THREADS; i++)
pthread_create (&threads[i], NULL, child_function, (void *) (uintptr_t) i);
/* Wait for child threads to reach child_sub_function. */
for (i = 0; i < NUM_THREADS; i++)
while (!unblock_main[i])
;
volatile int dummy = 0;
while (1)
/* Dummy loop body to allow setting breakpoint. */
dummy = !dummy; /* main break line */
return 0;
}