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b7b1008c0b
If we make GDB report the process EXIT event for the leader thread, as will be done in a latter patch of this series, then gdb.threads/current-lwp-dead.exp starts failing: (gdb) break fn_return Breakpoint 2 at 0x5555555551b5: file /home/pedro/rocm/gdb/build/gdb/testsuite/../../../src/gdb/testsuite/gdb.threads/current-lwp-dead.c, line 45. (gdb) continue Continuing. [New LWP 2138466] [Inferior 1 (process 2138459) exited normally] (gdb) FAIL: gdb.threads/current-lwp-dead.exp: continue to breakpoint: fn_return (the program exited) The inferior exit reported is actually correct. The main thread has indeed exited, and that's the thread that has the right exit code to report to the user, as that's the exit code that is reported to the program's parent. In this case, GDB managed to collect the exit code for the leader thread before reaping the other thread, because in reality, the testcase isn't creating standard threads, it is using raw clone, and the new clones are put in their own thread group. Fix it by making the main "thread" not exit until the scenario we're exercising plays out. Also, run the program to completion for completeness. The original program really wanted the leader thread to exit before the fn_return function was reached -- it was important that the current thread as pointed by inferior_ptid was gone when infrun got the breakpoint event. I've tweaked the testcase to ensure that that condition is still held, though it is no longer the main thread that exits. This required a bit of synchronization between the threads, which required using CLONE_VM unconditionally. The #ifdef guards were added as a fix for https://sourceware.org/bugzilla/show_bug.cgi?id=11214, though I don't think they were necessary because the program is not using TLS. If it turns out they were necessary, we can link the testcase with "-z now" instead, which was mentioned as an alternative workaround in that Bugzilla. Change-Id: I7be2f0da4c2fe8f80a60bdde5e6c623d8bd5a0aa
122 lines
3.4 KiB
C
122 lines
3.4 KiB
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 2009-2022 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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The original issue we're trying to test is described in this
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thread:
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https://sourceware.org/legacy-ml/gdb-patches/2009-06/msg00802.html
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The NEW_THREAD_EVENT code the comments below refer to no longer
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exists in GDB, so the following comments are kept for historical
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reasons, and to guide future updates to the testcase.
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---
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Do not use threads as we need to exploit a bug in LWP code masked by the
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threads code otherwise.
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INFERIOR_PTID must point to exited LWP. Here we use the initial LWP as it
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is automatically INFERIOR_PTID for GDB.
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Finally we need to call target_resume (RESUME_ALL, ...) which we invoke by
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NEW_THREAD_EVENT (called from the new LWP as initial LWP is exited now). */
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#define _GNU_SOURCE
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#include <sched.h>
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#include <assert.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#define STACK_SIZE 0x1000
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/* True if the 'fn_return' thread has been reached at the point after
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its parent is already gone. */
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volatile int fn_return_reached = 0;
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/* True if the 'fn' thread has exited. */
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volatile int fn_exited = 0;
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/* Wrapper around clone. */
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static int
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do_clone (int (*fn)(void *))
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{
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unsigned char *stack;
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int new_pid;
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stack = malloc (STACK_SIZE);
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assert (stack != NULL);
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new_pid = clone (fn, stack + STACK_SIZE, CLONE_FILES | CLONE_VM,
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NULL, NULL, NULL, NULL);
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assert (new_pid > 0);
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return new_pid;
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}
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static int
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fn_return (void *unused)
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{
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/* Wait until our direct parent exits. We want the breakpoint set a
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couple lines below to hit with the previously-selected thread
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gone. */
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while (!fn_exited)
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usleep (1);
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fn_return_reached = 1; /* at-fn_return */
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return 0;
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}
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static int
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fn (void *unused)
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{
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do_clone (fn_return);
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return 0;
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}
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int
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main (int argc, char **argv)
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{
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int new_pid, status, ret;
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new_pid = do_clone (fn);
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/* Note the clone call above didn't use CLONE_THREAD, so it actually
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put the new child in a new thread group. However, the new clone
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is still reported with PTRACE_EVENT_CLONE to GDB, since we didn't
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use CLONE_VFORK (results in PTRACE_EVENT_VFORK) nor set the
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termination signal to SIGCHLD (results in PTRACE_EVENT_FORK), so
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GDB thinks of it as a new thread of the same inferior. It's a
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bit of an odd setup, but it's not important for what we're
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testing, and, it let's us conveniently use waitpid to wait for
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the child, which you can't with CLONE_THREAD. */
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ret = waitpid (new_pid, &status, __WALL);
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assert (ret == new_pid);
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assert (WIFEXITED (status) && WEXITSTATUS (status) == 0);
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fn_exited = 1;
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/* Don't exit before the breakpoint at fn_return triggers. */
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while (!fn_return_reached)
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usleep (1);
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return 0;
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}
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