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ced2dffbf1
This commit fixes detaching on Linux when some thread exits the whole
thread group (process) just while we're detaching.
On Linux, a ptracer must detach from each LWP individually, with
PTRACE_DETACH. Since PTRACE_DETACH sets the thread running free, if
one of the already-detached threads causes the whole thread group to
exit (e.g., simply calls exit), the kernel force-kills the other
threads in the group, making them zombie, just as we're still
detaching them. Since PTRACE_DETACH against a zombie thread fails
with ESRCH, and gdb/gdbserver are not expecting this, the detach fails
with an error like: "Can't detach process: No such process.".
This patch detects this detach failure as normal, and instead of
erroring out, reaps the now-dead thread.
New test included, that exercises several different scenarios that
cause GDB/GDBserver to error out when it should not.
Tested on x86-64 GNU/Linux with {unix, native-gdbserver,
native-extended-gdbserver}
Note: without the previous fix, the "single-process + continue"
variant of the new test would fail with:
(gdb) PASS: gdb.threads/process-dies-while-detaching.exp: single-process: continue: watchpoint: switch to parent
continue
Continuing.
Warning:
Could not insert hardware watchpoint 3.
Could not insert hardware breakpoints:
You may have requested too many hardware breakpoints/watchpoints.
Command aborted.
(gdb) FAIL: gdb.threads/process-dies-while-detaching.exp: single-process: continue: watchpoint: continue
gdb/gdbserver/ChangeLog:
2016-07-01 Pedro Alves <palves@redhat.com>
Antoine Tremblay <antoine.tremblay@ericsson.com>
* linux-low.c: Change interface to take the target lwp_info
pointer directly and return void. Handle detaching from a zombie
thread.
(linux_detach_lwp_callback): New function.
(linux_detach): Detach from the leader thread after detaching from
the clone threads.
gdb/ChangeLog:
2016-07-01 Pedro Alves <palves@redhat.com>
Antoine Tremblay <antoine.tremblay@ericsson.com>
* inf-ptrace.c (inf_ptrace_detach_success): New function, factored
out from ...
(inf_ptrace_detach): ... here.
* inf-ptrace.h (inf_ptrace_detach_success): New declaration.
* linux-nat.c (get_pending_status): Rename to ...
(get_detach_signal): ... this, and return a host signal instead of
filling in a wait status.
(detach_one_lwp): New function, factored out from detach_callback
and adjusted to handle detaching from a zombie thread.
(detach_callback): Skip the leader thread.
(linux_nat_detach): No longer defer to inf_ptrace_detach to detach
the leader thread, nor build a signal string to pass down.
Instead, use target_announce_detach, detach_one_lwp and
inf_ptrace_detach_success.
gdb/testsuite/ChangeLog:
2016-07-01 Pedro Alves <palves@redhat.com>
Antoine Tremblay <antoine.tremblay@ericsson.com>
* gdb.threads/process-dies-while-detaching.c: New file.
* gdb.threads/process-dies-while-detaching.exp: New file.
117 lines
2.5 KiB
C
117 lines
2.5 KiB
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 2016 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 <stdlib.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <assert.h>
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/* This barrier ensures we only reach the initial breakpoint after all
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threads have started. */
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pthread_barrier_t start_threads_barrier;
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/* Many threads in order to be fairly sure the process exits while GDB
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is detaching from each thread in the process, on targets that need
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to detach from each thread individually. */
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#define NTHREADS 256
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/* GDB sets a watchpoint here. */
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int globalvar = 1;
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/* GDB reads this. */
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int mypid;
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/* Threads' entry point. */
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void *
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thread_function (void *arg)
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{
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pthread_barrier_wait (&start_threads_barrier);
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_exit (0);
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}
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/* The fork child's entry point. */
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void
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child_function (void)
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{
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pthread_t threads[NTHREADS];
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int i;
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pthread_barrier_init (&start_threads_barrier, NULL, NTHREADS + 1);
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for (i = 0; i < NTHREADS; i++)
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pthread_create (&threads[i], NULL, thread_function, NULL);
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pthread_barrier_wait (&start_threads_barrier);
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exit (0);
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}
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/* This is defined by the .exp file if testing the multi-process
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variant. */
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#ifdef MULTIPROCESS
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/* The fork parent's entry point. */
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void
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parent_function (pid_t child)
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{
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int status, ret;
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alarm (300);
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ret = waitpid (child, &status, 0);
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if (ret == -1)
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exit (1);
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else if (!WIFEXITED (status))
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exit (2);
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else
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{
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printf ("exited, status=%d\n", WEXITSTATUS (status));
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exit (0);
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}
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}
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#endif
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int
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main (void)
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{
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#ifdef MULTIPROCESS
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pid_t child;
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child = fork ();
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if (child == -1)
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return 1;
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#endif
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mypid = getpid ();
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#ifdef MULTIPROCESS
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if (child != 0)
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parent_function (child);
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else
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#endif
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child_function ();
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/* Not reached. */
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abort ();
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}
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