27f9f64975
The test introduced by this patch would fail in this configuration, with
the native-gdbserver or native-extended-gdbserver boards:
FAIL: gdb.threads/next-fork-other-thread.exp: fork_func=fork: target-non-stop=auto: non-stop=off: displaced-stepping=auto: i=2: next to for loop
The problem is that the step operation is forgotten when handling the
fork/vfork. With "debug infrun" and "debug remote", it looks like this
(some lines omitted for brevity). We do the next:
[infrun] proceed: enter
[infrun] proceed: addr=0xffffffffffffffff, signal=GDB_SIGNAL_DEFAULT
[infrun] resume_1: step=1, signal=GDB_SIGNAL_0, trap_expected=0, current thread [4154304.4154304.0] at 0x5555555553bf
[infrun] do_target_resume: resume_ptid=4154304.0.0, step=1, sig=GDB_SIGNAL_0
[remote] Sending packet: $vCont;r5555555553bf,5555555553c4:p3f63c0.3f63c0;c:p3f63c0.-1#cd
[infrun] proceed: exit
We then handle a fork event:
[infrun] fetch_inferior_event: enter
[remote] wait: enter
[remote] Packet received: T05fork:p3f63ee.3f63ee;06:0100000000000000;07:b08e59f6ff7f0000;10:bf60e8f7ff7f0000;thread:p3f63c0.3f63c6;core:17;
[remote] wait: exit
[infrun] print_target_wait_results: target_wait (-1.0.0 [process -1], status) =
[infrun] print_target_wait_results: 4154304.4154310.0 [Thread 4154304.4154310],
[infrun] print_target_wait_results: status->kind = FORKED, child_ptid = 4154350.4154350.0
[infrun] handle_inferior_event: status->kind = FORKED, child_ptid = 4154350.4154350.0
[remote] Sending packet: $D;3f63ee#4b
[infrun] resume_1: step=0, signal=GDB_SIGNAL_0, trap_expected=0, current thread [4154304.4154310.0] at 0x7ffff7e860bf
[infrun] do_target_resume: resume_ptid=4154304.0.0, step=0, sig=GDB_SIGNAL_0
[remote] Sending packet: $vCont;c:p3f63c0.-1#73
[infrun] fetch_inferior_event: exit
In the first snippet, we resume the stepping thread with the range-stepping (r)
vCont command. But after handling the fork (detaching the fork child), we
resumed the whole process freely. The stepping thread, which was paused by
GDBserver while reporting the fork event, was therefore resumed freely, instead
of confined to the addresses of the stepped line. Note that since this
is a "next", it could be that we have entered a function, installed a
step-resume breakpoint, and it's ok to continue freely the stepping
thread, but that's not the case here. The two snippets shown above were
next to each other in the logs.
For the fork case, we can resume stepping right after handling the
event.
However, for the vfork case, where we are waiting for the
external child process to exec or exit, we only resume the thread that
called vfork, and keep the others stopped (see patch "gdb: fix handling of
vfork by multi-threaded program" prior in this series). So we can't
resume the stepping thread right now. Instead, do it after handling the
vfork-done event.
Change-Id: I92539c970397ce880110e039fe92b87480f816bd
92 lines
2.1 KiB
C
92 lines
2.1 KiB
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 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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#include <pthread.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <errno.h>
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#include <assert.h>
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#include <limits.h>
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/* Number of threads doing forks. */
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#define N_FORKERS 4
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static void *
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forker (void *arg)
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{
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for (;;)
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{
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pid_t pid = FORK_FUNC ();
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if (pid == 0)
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_exit (11);
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assert (pid > 0);
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/* Wait for children to exit. */
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int ret;
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int stat;
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do
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{
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ret = waitpid (pid, &stat, 0);
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} while (ret == EINTR);
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assert (ret == pid);
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assert (WIFEXITED (stat));
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assert (WEXITSTATUS (stat) == 11);
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/* We need a sleep, otherwise the forking threads spam events and the
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stepping thread doesn't make progress. Sleep for a bit less than
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`sleep_a_bit` does, so that forks are likely to interrupt a "next". */
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usleep (40 * 1000);
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}
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return NULL;
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}
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static void
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sleep_a_bit (void)
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{
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usleep (1000 * 50);
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}
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int
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main (void)
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{
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int i;
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alarm (60);
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pthread_t thread[N_FORKERS];
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for (i = 0; i < N_FORKERS; ++i)
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{
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int ret = pthread_create (&thread[i], NULL, forker, NULL);
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assert (ret == 0);
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}
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for (i = 0; i < INT_MAX; ++i) /* for loop */
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{
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sleep_a_bit (); /* break here */
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sleep_a_bit (); /* other line */
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}
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for (i = 0; i < N_FORKERS; ++i)
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pthread_join (thread[i], NULL);
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return 0;
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}
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