GDBserver crashes when killing a multi-thread process
Here's an example, with the new test: gdbserver :9999 gdb.threads/kill gdb gdb.threads/kill (gdb) b 52 Breakpoint 1 at 0x4007f4: file kill.c, line 52. Continuing. Breakpoint 1, main () at kill.c:52 52 return 0; /* set break here */ (gdb) k Kill the program being debugged? (y or n) y gdbserver :9999 gdb.threads/kill Process gdb.base/watch_thread_num created; pid = 9719 Listening on port 1234 Remote debugging from host 127.0.0.1 Killing all inferiors Segmentation fault (core dumped) Backtrace: (gdb) bt #0 0x00000000004068a0 in find_inferior (list=0x66b060 <all_threads>, func=0x427637 <kill_one_lwp_callback>, arg=0x7fffffffd3fc) at src/gdb/gdbserver/inferiors.c:199 #1 0x00000000004277b6 in linux_kill (pid=15708) at src/gdb/gdbserver/linux-low.c:966 #2 0x000000000041354d in kill_inferior (pid=15708) at src/gdb/gdbserver/target.c:163 #3 0x00000000004107e9 in kill_inferior_callback (entry=0x6704f0) at src/gdb/gdbserver/server.c:2934 #4 0x0000000000406522 in for_each_inferior (list=0x66b050 <all_processes>, action=0x4107a6 <kill_inferior_callback>) at src/gdb/gdbserver/inferiors.c:57 #5 0x0000000000412377 in process_serial_event () at src/gdb/gdbserver/server.c:3767 #6 0x000000000041267c in handle_serial_event (err=0, client_data=0x0) at src/gdb/gdbserver/server.c:3880 #7 0x00000000004189ff in handle_file_event (event_file_desc=4) at src/gdb/gdbserver/event-loop.c:434 #8 0x00000000004181c6 in process_event () at src/gdb/gdbserver/event-loop.c:189 #9 0x0000000000418f45 in start_event_loop () at src/gdb/gdbserver/event-loop.c:552 #10 0x0000000000411272 in main (argc=3, argv=0x7fffffffd8d8) at src/gdb/gdbserver/server.c:3283 The problem is that linux_wait_for_event deletes lwps that have exited (even those not passed in as lwps of interest), while the lwp/thread list is being walked on with find_inferior. find_inferior can handle the current iterated inferior being deleted, but not others. When killing lwps, we don't really care about any of the pending status handling of linux_wait_for_event. We can just waitpid the lwps directly, which is also what GDB does (see linux-nat.c:kill_wait_callback). This way the lwps are not deleted while we're walking the list. They'll be deleted by linux_mourn afterwards. This crash triggers several times when running the testsuite against GDBserver with the native-gdbserver board (target remote), but as GDB can't distinguish between GDBserver crashing and "kill" being sucessful, as in both cases the connection is closed (the 'k' packet doesn't require a reply), and the inferior is gone, that results in no FAIL. The patch adds a generic test that catches the issue with extended-remote mode (and works fine with native testing too). Here's how it fails with the native-extended-gdbserver board without the fix: (gdb) info threads Id Target Id Frame 6 Thread 15367.15374 0x000000373bcbc98d in nanosleep () at ../sysdeps/unix/syscall-template.S:81 5 Thread 15367.15373 0x000000373bcbc98d in nanosleep () at ../sysdeps/unix/syscall-template.S:81 4 Thread 15367.15372 0x000000373bcbc98d in nanosleep () at ../sysdeps/unix/syscall-template.S:81 3 Thread 15367.15371 0x000000373bcbc98d in nanosleep () at ../sysdeps/unix/syscall-template.S:81 2 Thread 15367.15370 0x000000373bcbc98d in nanosleep () at ../sysdeps/unix/syscall-template.S:81 * 1 Thread 15367.15367 main () at .../gdb.threads/kill.c:52 (gdb) kill Kill the program being debugged? (y or n) y Remote connection closed ^^^^^^^^^^^^^^^^^^^^^^^^ (gdb) FAIL: gdb.threads/kill.exp: kill Extended remote should remain connected after the kill. gdb/gdbserver/ 2014-07-11 Pedro Alves <palves@redhat.com> * linux-low.c (kill_wait_lwp): New function, based on kill_one_lwp_callback, but use my_waitpid directly. (kill_one_lwp_callback, linux_kill): Use it. gdb/testsuite/ 2014-07-11 Pedro Alves <palves@redhat.com> * gdb.threads/kill.c: New file. * gdb.threads/kill.exp: New file.
This commit is contained in:
Pedro Alves
parent
b9c1d481cc
commit
e76126e8d1
5 changed files with 194 additions and 26 deletions
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@ -1,3 +1,9 @@
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2014-07-11 Pedro Alves <palves@redhat.com>
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* linux-low.c (kill_wait_lwp): New function, based on
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kill_one_lwp_callback, but use my_waitpid directly.
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(kill_one_lwp_callback, linux_kill): Use it.
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2014-06-23 Pedro Alves <palves@redhat.com>
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* linux-x86-low.c (x86_linux_prepare_to_resume): Clear DR_CONTROL
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@ -909,6 +909,46 @@ linux_kill_one_lwp (struct lwp_info *lwp)
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errno ? strerror (errno) : "OK");
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}
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/* Kill LWP and wait for it to die. */
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static void
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kill_wait_lwp (struct lwp_info *lwp)
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{
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struct thread_info *thr = get_lwp_thread (lwp);
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int pid = ptid_get_pid (ptid_of (thr));
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int lwpid = ptid_get_lwp (ptid_of (thr));
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int wstat;
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int res;
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if (debug_threads)
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debug_printf ("kwl: killing lwp %d, for pid: %d\n", lwpid, pid);
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do
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{
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linux_kill_one_lwp (lwp);
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/* Make sure it died. Notes:
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- The loop is most likely unnecessary.
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- We don't use linux_wait_for_event as that could delete lwps
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while we're iterating over them. We're not interested in
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any pending status at this point, only in making sure all
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wait status on the kernel side are collected until the
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process is reaped.
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- We don't use __WALL here as the __WALL emulation relies on
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SIGCHLD, and killing a stopped process doesn't generate
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one, nor an exit status.
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*/
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res = my_waitpid (lwpid, &wstat, 0);
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if (res == -1 && errno == ECHILD)
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res = my_waitpid (lwpid, &wstat, __WCLONE);
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} while (res > 0 && WIFSTOPPED (wstat));
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gdb_assert (res > 0);
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}
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/* Callback for `find_inferior'. Kills an lwp of a given process,
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except the leader. */
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@ -917,7 +957,6 @@ kill_one_lwp_callback (struct inferior_list_entry *entry, void *args)
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{
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struct thread_info *thread = (struct thread_info *) entry;
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struct lwp_info *lwp = get_thread_lwp (thread);
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int wstat;
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int pid = * (int *) args;
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if (ptid_get_pid (entry->id) != pid)
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@ -936,14 +975,7 @@ kill_one_lwp_callback (struct inferior_list_entry *entry, void *args)
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return 0;
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}
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do
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{
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linux_kill_one_lwp (lwp);
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/* Make sure it died. The loop is most likely unnecessary. */
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pid = linux_wait_for_event (thread->entry.id, &wstat, __WALL);
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} while (pid > 0 && WIFSTOPPED (wstat));
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kill_wait_lwp (lwp);
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return 0;
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}
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@ -952,8 +984,6 @@ linux_kill (int pid)
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{
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struct process_info *process;
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struct lwp_info *lwp;
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int wstat;
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int lwpid;
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process = find_process_pid (pid);
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if (process == NULL)
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@ -976,21 +1006,7 @@ linux_kill (int pid)
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pid);
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}
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else
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{
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struct thread_info *thr = get_lwp_thread (lwp);
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if (debug_threads)
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debug_printf ("lk_1: killing lwp %ld, for pid: %d\n",
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lwpid_of (thr), pid);
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do
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{
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linux_kill_one_lwp (lwp);
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/* Make sure it died. The loop is most likely unnecessary. */
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lwpid = linux_wait_for_event (thr->entry.id, &wstat, __WALL);
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} while (lwpid > 0 && WIFSTOPPED (wstat));
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}
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kill_wait_lwp (lwp);
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the_target->mourn (process);
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@ -1,3 +1,8 @@
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2014-07-11 Pedro Alves <palves@redhat.com>
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* gdb.threads/kill.c: New file.
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* gdb.threads/kill.exp: New file.
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2014-07-10 Yao Qi <yao@codesourcery.com>
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* gdb.trace/tfile.c (write_basic_trace_file)
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64
gdb/testsuite/gdb.threads/kill.c
Normal file
64
gdb/testsuite/gdb.threads/kill.c
Normal file
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@ -0,0 +1,64 @@
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/* This testcase is part of GDB, the GNU debugger.
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Copyright 2014 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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#ifdef USE_THREADS
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#include <unistd.h>
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#include <pthread.h>
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#define NUM 5
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pthread_barrier_t barrier;
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void *
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thread_function (void *arg)
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{
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volatile unsigned int counter = 1;
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pthread_barrier_wait (&barrier);
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while (counter > 0)
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{
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counter++;
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usleep (1);
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}
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pthread_exit (NULL);
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}
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#endif /* USE_THREADS */
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void
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setup (void)
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{
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#ifdef USE_THREADS
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pthread_t threads[NUM];
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int i;
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pthread_barrier_init (&barrier, NULL, NUM + 1);
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for (i = 0; i < NUM; i++)
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pthread_create (&threads[i], NULL, thread_function, NULL);
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pthread_barrier_wait (&barrier);
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#endif /* USE_THREADS */
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}
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int
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main (void)
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{
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setup ();
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return 0; /* set break here */
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}
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77
gdb/testsuite/gdb.threads/kill.exp
Normal file
77
gdb/testsuite/gdb.threads/kill.exp
Normal file
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@ -0,0 +1,77 @@
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# This testcase is part of GDB, the GNU debugger.
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# Copyright 2014 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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#
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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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#
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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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standard_testfile
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# Run the test proper. THREADED indicates whether to build a threaded
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# program and spawn several threads before trying to kill the program.
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proc test {threaded} {
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global testfile srcfile
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with_test_prefix [expr ($threaded)?"threaded":"non-threaded"] {
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set options {debug}
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if {$threaded} {
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lappend options "pthreads"
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lappend options "additional_flags=-DUSE_THREADS"
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set prog ${testfile}_threads
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} else {
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set prog ${testfile}_nothreads
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}
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if {[prepare_for_testing "failed to prepare" $prog $srcfile $options] == -1} {
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return -1
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}
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if { ![runto main] } then {
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fail "run to main"
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return
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}
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set linenum [gdb_get_line_number "set break here"]
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gdb_breakpoint "$srcfile:$linenum"
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gdb_continue_to_breakpoint "break here" ".*break here.*"
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if {$threaded} {
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gdb_test "info threads" "6.*5.*4.*3.*2.*1.*" "all threads started"
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}
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# This kills and ensures no output other than the prompt comes out,
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# like:
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#
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# (gdb) kill
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# Kill the program being debugged? (y or n) y
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# (gdb)
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#
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# If we instead saw more output, like e.g., with an extended-remote
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# connection:
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#
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# (gdb) kill
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# Kill the program being debugged? (y or n) y
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# Remote connection closed
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# (gdb)
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#
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# the above would mean that the remote end crashed.
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gdb_test "kill" "^y" "kill program" "Kill the program being debugged\\? \\(y or n\\) $" "y"
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}
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}
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foreach threaded {true false} {
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test $threaded
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}
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