Ref: https://sourceware.org/ml/gdb-patches/2015-08/msg00675.html
If multiprocess extensions are off (because specific gdbserver port
doesn't support them), then when gdbserver doesn't have a thread
selected yet, and GDB sends Hg packet to select one, gdbserver
crashes. That's because extracting the desired thread id out of the
packet that GDB sent depends on the current thread to fill in the
missing process id ... Fix this by getting the process id from the
first (and only) process in the processes list instead.
The GNU/Linux port doesn't trip on this because it always runs with
multiprocess extensions enabled. To make it easier to catch such
regressions going forward, this commit also adds a new smoke test that
spawns gdbserver, connects to it and runs to main with the
multiprocess extensions force-disabled.
gdb/gdbserver/ChangeLog:
2015-08-24 Pedro Alves <palves@redhat.com>
* inferiors.c (get_first_process): New function.
* inferiors.h (get_first_process): New declaration.
* remote-utils.c (read_ptid): Default to the first process in the
list, instead of to the current thread's process.
gdb/testsuite/ChangeLog:
2015-08-24 Pedro Alves <palves@redhat.com>
* gdb.server/connect-without-multi-process.c: New file.
* gdb.server/connect-without-multi-process.exp: New file.
The regcache used to be hidden inside inferiors.c, but since the
tracepoints support that it's a first class object. This also fixes a
few implicit pointer conversion errors in C++ mode, caused by a few
places missing the explicit cast.
gdb/gdbserver/ChangeLog:
2015-08-06 Pedro Alves <palves@redhat.com>
* gdbthread.h (struct regcache): Forward declare.
(struct thread_info) <regcache_data>: Now a struct regcache
pointer.
* inferiors.c (inferior_regcache_data)
(set_inferior_regcache_data): Now work with struct regcache
pointers.
* inferiors.h (struct regcache): Forward declare.
(inferior_regcache_data, set_inferior_regcache_data): Now work
with struct regcache pointers.
* regcache.c (get_thread_regcache, regcache_invalidate_thread)
(free_register_cache_thread): Remove struct regcache pointer
casts.
This patch renames symbols that happen to have names which are
reserved keywords in C++.
Most of this was generated with Tromey's cxx-conversion.el script.
Some places where later hand massaged a bit, to fix formatting, etc.
And this was rebased several times meanwhile, along with re-running
the script, so re-running the script from scratch probably does not
result in the exact same output. I don't think that matters anyway.
gdb/
2015-02-27 Tom Tromey <tromey@redhat.com>
Pedro Alves <palves@redhat.com>
Rename symbols whose names are reserved C++ keywords throughout.
gdb/gdbserver/
2015-02-27 Tom Tromey <tromey@redhat.com>
Pedro Alves <palves@redhat.com>
Rename symbols whose names are reserved C++ keywords throughout.
GDB has a function named "current_inferior" and gdbserver has a global
variable named "current_inferior", but the two are not equivalent;
indeed, gdbserver does not have any real equivalent of what GDB calls
an inferior. What gdbserver's "current_inferior" is actually pointing
to is a structure describing the current thread. This commit renames
current_inferior as current_thread in gdbserver to clarify this. It
also renames the function "set_desired_inferior" to "set_desired_thread"
and renames various local variables from foo_inferior to foo_thread.
gdb/gdbserver/ChangeLog:
* inferiors.h (current_inferior): Renamed as...
(current_thread): New variable. All uses updated.
* linux-low.c (get_pc): Renamed saved_inferior as saved_thread.
(maybe_move_out_of_jump_pad): Likewise.
(cancel_breakpoint): Likewise.
(linux_low_filter_event): Likewise.
(wait_for_sigstop): Likewise.
(linux_resume_one_lwp): Likewise.
(need_step_over_p): Likewise.
(start_step_over): Likewise.
(linux_stabilize_threads): Renamed save_inferior as saved_thread.
* linux-x86-low.c (x86_linux_update_xmltarget): Likewise.
* proc-service.c (ps_lgetregs): Renamed reg_inferior as reg_thread
and save_inferior as saved_thread.
* regcache.c (get_thread_regcache): Renamed saved_inferior as
saved_thread.
(regcache_invalidate_thread): Likewise.
* remote-utils.c (prepare_resume_reply): Likewise.
* thread-db.c (thread_db_get_tls_address): Likewise.
(disable_thread_event_reporting): Likewise.
(remove_thread_event_breakpoints): Likewise.
* tracepoint.c (gdb_agent_about_to_close): Renamed save_inferior
as saved_thread.
* target.h (set_desired_inferior): Renamed as...
(set_desired_thread): New declaration. All uses updated.
* server.c (myresume): Updated comment to reference thread instead
of inferior.
(handle_serial_event): Likewise.
(handle_target_event): Likewise.
GDBserver currently hangs forever in waitpid if the leader thread
exits before other threads, or if all resumed threads exit - e.g.,
next over a thread exit with sched-locking on. This is exposed by
leader-exit.exp. leader-exit.exp is part of a series of tests for a
set of related problems. See
<http://www.sourceware.org/ml/gdb-patches/2011-10/msg00704.html>:
"
To recap, on the Linux kernel, ptrace/waitpid don't allow reaping the
leader thread until all other threads in the group are reaped. When
the leader exits, it goes zombie, but waitpid will not return an exit
status until the other threads are gone. This is presently exercised
by the gdb.threads/leader-exit.exp test. The fix for that test, in
linux-nat.c:wait_lwp, handles the case where we see the leader gone
when we're stopping all threads to report an event to some other
thread to the core.
(...)
The latter bit about not blocking if there no resumed threads in the
process also applies to some other thread exiting, not just the main
thread. E.g., this test starts a thread, and runs to a breakpoint in
that thread:
...
(gdb) c
Continuing.
[New Thread 0x7ffff75a4700 (LWP 23397)]
[Switching to Thread 0x7ffff75a4700 (LWP 23397)]
Breakpoint 2, thread_a (arg=0x0) at ../../../src/gdb/testsuite/gdb.threads/no-unwaited-for-left.c:28
28 return 0; /* break-here */
(gdb) info threads
* 2 Thread 0x7ffff75a4700 (LWP 23397) thread_a (arg=0x0) at ../../../src/gdb/testsuite/gdb.threads/no-unwaited-for-left.c:28
1 Thread 0x7ffff7fcb720 (LWP 23391) 0x00007ffff7bc606d in pthread_join (threadid=140737343276800, thread_return=0x0) at pthread_join.c:89
The thread will exit as soon as we resume it. But if we only resume
that thread, leaving the rest of the threads stopped:
(gdb) set scheduler-locking on
(gdb) c
Continuing.
^C^C^C^C^C^C^C^C
"
This patch fixes the issues by implementing TARGET_WAITKIND_NO_RESUMED
on GDBserver, similarly to what the patch above did for native
Linux GDB.
gdb.threads/leader-exit.exp now passes.
gdb.threads/no-unwaited-for-left.exp now at least errors out instead
of hanging:
continue
Continuing.
warning: Remote failure reply: E.No unwaited-for children left.
[Thread 15454] #1 stopped.
0x00000034cf408e60 in pthread_join (threadid=140737353922368, thread_return=0x0) at pthread_join.c:93
93 lll_wait_tid (pd->tid);
(gdb) FAIL: gdb.threads/no-unwaited-for-left.exp: continue stops when the main thread exits
The gdb.threads/non-ldr-exc-*.exp tests are skipped because GDBserver
unfortunately doesn't support fork/exec yet, but I'm confident this
fixes the related issues.
I'm leaving modeling TARGET_WAITKIND_NO_RESUMED in the RSP for a
separate pass.
(BTW, in case of error in response to a vCont, it would be better for
GDB to query the target for the current thread, or re-select one,
instead of assuming current inferior_ptid is still the selected
thread.)
This implementation is a little different from GDB's, because I'm
avoiding bringing in more of this broken use of waitpid(PID) into
GDBserver. Specifically, this avoids waitpid(PID) when stopping all
threads. There's really no need for wait_for_sigstop to wait for each
LWP in turn. Instead, with some refactoring, we make it reuse
linux_wait_for_event.
gdb/gdbserver/
2014-02-27 Pedro Alves <palves@redhat.com>
PR 12702
* inferiors.h (A_I_NEXT, ALL_INFERIORS_TYPE, ALL_PROCESSES): New
macros.
* linux-low.c (delete_lwp, handle_extended_wait): Add debug
output.
(last_thread_of_process_p): Take a PID argument instead of a
thread pointer.
(linux_wait_for_lwp): Delete.
(num_lwps, check_zombie_leaders, not_stopped_callback): New
functions.
(linux_low_filter_event): New function, party factored out from
linux_wait_for_event.
(linux_wait_for_event): Rename to ...
(linux_wait_for_event_filtered): ... this. Add new filter ptid
argument. Partly rewrite. Always use waitpid(-1, WNOHANG) and
sigsuspend. Check for zombie leaders.
(linux_wait_for_event): Reimplement as wrapper around
linux_wait_for_event_filtered.
(linux_wait_1): Handle TARGET_WAITKIND_NO_RESUMED. Assume that if
a normal or signal exit is seen, it's the whole process exiting.
(wait_for_sigstop): No longer a for_each_inferior callback.
Rewrite on top of linux_wait_for_event_filtered.
(stop_all_lwps): Call wait_for_sigstop directly.
* server.c (resume, handle_target_event): Handle
TARGET_WAITKIND_NO_RESUMED.
* dll.c (clear_dlls): Replace accessing list implemention details
with API function.
* gdbthread.h (get_first_thread): Declare.
* inferiors.c (for_each_inferior_with_data): New function.
(get_first_thread): New function.
(find_thread_ptid): Simplify.
(get_first_inferior): New function.
(clear_list): Delete.
(one_inferior_p): New function.
(clear_inferior_list): New function.
(clear_inferiors): Update.
* inferiors.h (for_each_inferior_with_data): Declare.
(clear_inferior_list): Declare.
(one_inferior_p): Declare.
(get_first_inferior): Declare.
* linux-low.c (linux_wait_for_event): Replace accessing list
implemention details with API function.
* server.c (target_running): Ditto.
(accumulate_file_name_length): New function.
(emit_dll_description): New function.
(handle_qxfer_libraries): Replace accessing list implemention
details with API function.
(handle_qxfer_threads_worker): New function.
(handle_qxfer_threads_proper): Replace accessing list implemention
details with API function.
(handle_query): Ditto.
(visit_actioned_threads_callback_ftype): New typedef.
(visit_actioned_threads_data): New struct.
(visit_actioned_threads): Rewrite to be find_inferior callback.
(resume): Call find_inferior.
(handle_status): Replace accessing list implemention
details with API function.
(process_serial_event): Replace accessing list implemention details
with API function.
* target.c (set_desired_inferior): Replace accessing list implemention
details with API function.
* tracepoint.c (same_process_p): New function.
(gdb_agent_about_to_close): Replace accessing list implemention
details with API function.
* win32-low.c (child_delete_thread): Replace accessing list
implemention details with API function.
(match_dll_by_basename): New function.
(dll_is_loaded_by_basename): New function.
(win32_ensure_ntdll_loaded): Replace accessing list implemention
details call to dll_is_loaded_by_basename.
Pedro Alves
Joel Brobecker
Gary Benson
Doug Evans