old-cross-binutils/gdb/testsuite/gdb.threads/kill.exp
Pedro Alves e76126e8d1 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.
2014-07-11 11:07:13 +01:00

77 lines
2.1 KiB
Text

# This testcase is part of GDB, the GNU debugger.
# Copyright 2014 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/>. */
standard_testfile
# Run the test proper. THREADED indicates whether to build a threaded
# program and spawn several threads before trying to kill the program.
proc test {threaded} {
global testfile srcfile
with_test_prefix [expr ($threaded)?"threaded":"non-threaded"] {
set options {debug}
if {$threaded} {
lappend options "pthreads"
lappend options "additional_flags=-DUSE_THREADS"
set prog ${testfile}_threads
} else {
set prog ${testfile}_nothreads
}
if {[prepare_for_testing "failed to prepare" $prog $srcfile $options] == -1} {
return -1
}
if { ![runto main] } then {
fail "run to main"
return
}
set linenum [gdb_get_line_number "set break here"]
gdb_breakpoint "$srcfile:$linenum"
gdb_continue_to_breakpoint "break here" ".*break here.*"
if {$threaded} {
gdb_test "info threads" "6.*5.*4.*3.*2.*1.*" "all threads started"
}
# This kills and ensures no output other than the prompt comes out,
# like:
#
# (gdb) kill
# Kill the program being debugged? (y or n) y
# (gdb)
#
# If we instead saw more output, like e.g., with an extended-remote
# connection:
#
# (gdb) kill
# Kill the program being debugged? (y or n) y
# Remote connection closed
# (gdb)
#
# the above would mean that the remote end crashed.
gdb_test "kill" "^y" "kill program" "Kill the program being debugged\\? \\(y or n\\) $" "y"
}
}
foreach threaded {true false} {
test $threaded
}