From: Pedro Alves <pedro@palves.net>
To: Andrew Burgess <aburgess@redhat.com>, gdb-patches@sourceware.org
Subject: Re: [PATCH 14/31] all-stop/synchronous RSP support thread-exit events
Date: Mon, 13 Nov 2023 14:11:51 +0000 [thread overview]
Message-ID: <12c28313-3dac-46d5-b536-d71d5c9c7bbc@palves.net> (raw)
In-Reply-To: <87zg5byxal.fsf@redhat.com>
On 2023-06-07 18:52, Andrew Burgess wrote:
> Pedro Alves <pedro@palves.net> writes:
>
>> Currently, GDB does not understand the THREAD_EXITED stop reply in
>> remote all-stop mode. There's no good reason for this, it just
>> happened that THREAD_EXITED was only ever reported in non-stop mode so
>> far. This patch teaches GDB to parse that event in all-stop RSP too.
>> There is no need to add a qSupported feature for this, because the
>> server won't send a THREAD_EXITED event unless GDB explicitly asks for
>> it, with QThreadEvents, or with the GDB_THREAD_OPTION_EXIT
>> QThreadOptions option added in the next patch.
>>
>> Change-Id: Ide5d12391adf432779fe4c79526801c4a5630966
>> ---
>> gdb/remote.c | 5 +++--
>> gdbserver/server.cc | 1 +
>> 2 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/gdb/remote.c b/gdb/remote.c
>> index 9de8ed8a068..f7ab8523fd5 100644
>> --- a/gdb/remote.c
>> +++ b/gdb/remote.c
>> @@ -8172,7 +8172,8 @@ remote_target::process_stop_reply (struct stop_reply *stop_reply,
>> && status->kind () != TARGET_WAITKIND_NO_RESUMED)
>> {
>> /* Expedited registers. */
>> - if (!stop_reply->regcache.empty ())
>> + if (status->kind () != TARGET_WAITKIND_THREAD_EXITED
>> + && !stop_reply->regcache.empty ())
>
> I haven't investigated if this crops up, but, inside the if block we
> call xfree to release some of the regcache data.
>
> If it was ever the case the status->kind() was THREAD_EXITED, and the
> regcache was not empty, would we then leak memory?
THREAD_EXITED stop replies can't carry expedited registers, they're not
a kind of T stop reply, they're their own stop reply kind. They're just:
@anchor{thread exit event}
@cindex thread exit event, remote reply
@item w @var{AA} ; @var{tid}
The thread exited, and @var{AA} is the exit status. This response
should not be sent by default; @value{GDBN} requests it with the
@ref{QThreadEvents} packet. See also @ref{thread create event} above.
@var{AA} is formatted as a big-endian hex string.
But even if a remote server included them somehow, we wouldn't parse them:
case 'w': /* Thread exited. */
{
ULONGEST value;
p = unpack_varlen_hex (&buf[1], &value);
event->ws.set_thread_exited (value);
if (*p != ';')
error (_("stop reply packet badly formatted: %s"), buf);
event->ptid = read_ptid (++p, NULL);
break;
}
I don't remember exactly why I added the "status->kind () != TARGET_WAITKIND_THREAD_EXITED"
check, I think it was just because I was reading the code and noticed it doesn't make sense
to process expected registers for that event.
>
> If THREAD_EXITED implies that the regcache is empty could we use an
> assert here instead of adding the kind check to the if? Maybe:
>
> if (!stop_reply->regcache.empty ())
> {
> gdb_assert (status->kind () != TARGET_WAITKIND_THREAD_EXITED);
>
> ...
>
Makes sense, I did this.
> But maybe that's bad because we'd be making assert based on state that
> arrives from gdbserver.
As explained above, that can't happen, so an assertion is fine.
> In which case, should we perform some action to
> ensure that the regcache data is correctly freed?
I wrote a couple patches to improve ownership around this, using
unique_ptr more. I will post them after this series (need to write
commit logs, etc.)
next prev parent reply other threads:[~2023-11-13 14:11 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-12 20:30 [PATCH 00/31] Step over thread clone and thread exit Pedro Alves
2022-12-12 20:30 ` [PATCH 01/31] displaced step: pass down target_waitstatus instead of gdb_signal Pedro Alves
2023-02-03 10:44 ` Andrew Burgess
2023-03-10 17:15 ` Pedro Alves
2023-03-16 16:07 ` Andrew Burgess
2023-03-22 21:29 ` Andrew Burgess
2023-03-23 15:15 ` Pedro Alves
2023-03-27 12:40 ` Andrew Burgess
2023-03-27 16:21 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 02/31] linux-nat: introduce pending_status_str Pedro Alves
2023-02-03 12:00 ` Andrew Burgess
2023-03-10 17:15 ` Pedro Alves
2023-03-16 16:19 ` Andrew Burgess
2023-03-27 18:05 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 03/31] gdb/linux: Delete all other LWPs immediately on ptrace exec event Pedro Alves
2023-03-21 14:50 ` Andrew Burgess
2023-04-04 13:57 ` Pedro Alves
2023-04-14 19:29 ` Pedro Alves
2023-05-26 15:04 ` Andrew Burgess
2023-11-13 14:04 ` Pedro Alves
2023-05-26 14:45 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 04/31] Step over clone syscall w/ breakpoint, TARGET_WAITKIND_THREAD_CLONED Pedro Alves
2023-02-04 15:38 ` Andrew Burgess
2023-03-10 17:16 ` Pedro Alves
2023-03-21 16:06 ` Andrew Burgess
2023-11-13 14:05 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 05/31] Support clone events in the remote protocol Pedro Alves
2023-03-22 15:46 ` Andrew Burgess
2023-11-13 14:05 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 06/31] Avoid duplicate QThreadEvents packets Pedro Alves
2023-05-26 15:53 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 07/31] enum_flags to_string Pedro Alves
2023-01-30 20:07 ` Simon Marchi
2022-12-12 20:30 ` [PATCH 08/31] Thread options & clone events (core + remote) Pedro Alves
2023-01-31 12:25 ` Lancelot SIX
2023-03-10 19:16 ` Pedro Alves
2023-06-06 13:29 ` Andrew Burgess
2023-11-13 14:07 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 09/31] Thread options & clone events (native Linux) Pedro Alves
2023-06-06 13:43 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 10/31] Thread options & clone events (Linux GDBserver) Pedro Alves
2023-06-06 14:12 ` Andrew Burgess
2023-11-13 14:07 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 11/31] gdbserver: Hide and don't detach pending clone children Pedro Alves
2023-06-07 16:10 ` Andrew Burgess
2023-11-13 14:08 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 12/31] Remove gdb/19675 kfails (displaced stepping + clone) Pedro Alves
2023-06-07 17:08 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 13/31] Add test for stepping over clone syscall Pedro Alves
2023-06-07 17:42 ` Andrew Burgess
2023-11-13 14:09 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 14/31] all-stop/synchronous RSP support thread-exit events Pedro Alves
2023-06-07 17:52 ` Andrew Burgess
2023-11-13 14:11 ` Pedro Alves [this message]
2023-12-15 18:15 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 15/31] gdbserver/linux-low.cc: Ignore event_ptid if TARGET_WAITKIND_IGNORE Pedro Alves
2022-12-12 20:30 ` [PATCH 16/31] Move deleting thread on TARGET_WAITKIND_THREAD_EXITED to core Pedro Alves
2023-06-08 12:27 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 17/31] Introduce GDB_THREAD_OPTION_EXIT thread option, fix step-over-thread-exit Pedro Alves
2023-06-08 13:17 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 18/31] Implement GDB_THREAD_OPTION_EXIT support for Linux GDBserver Pedro Alves
2023-06-08 14:14 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 19/31] Implement GDB_THREAD_OPTION_EXIT support for native Linux Pedro Alves
2023-06-08 14:17 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 20/31] gdb: clear step over information on thread exit (PR gdb/27338) Pedro Alves
2023-06-08 15:29 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 21/31] stop_all_threads: (re-)enable async before waiting for stops Pedro Alves
2023-06-08 15:49 ` Andrew Burgess
2023-11-13 14:12 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 22/31] gdbserver: Queue no-resumed event after thread exit Pedro Alves
2023-06-08 18:16 ` Andrew Burgess
2023-11-13 14:12 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 23/31] Don't resume new threads if scheduler-locking is in effect Pedro Alves
2023-06-08 18:24 ` Andrew Burgess
2023-11-13 14:12 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 24/31] Report thread exit event for leader if reporting thread exit events Pedro Alves
2023-06-09 13:11 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 25/31] Ignore failure to read PC when resuming Pedro Alves
2023-06-10 10:33 ` Andrew Burgess
2023-11-13 14:13 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 26/31] gdb/testsuite/lib/my-syscalls.S: Refactor new SYSCALL macro Pedro Alves
2023-06-10 10:33 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 27/31] Testcases for stepping over thread exit syscall (PR gdb/27338) Pedro Alves
2023-06-12 9:53 ` Andrew Burgess
2022-12-12 20:30 ` [PATCH 28/31] Document remote clone events, and QThreadOptions packet Pedro Alves
2023-06-05 15:53 ` Andrew Burgess
2023-11-13 14:13 ` Pedro Alves
2023-06-12 12:06 ` Andrew Burgess
2023-11-13 14:15 ` Pedro Alves
2022-12-12 20:30 ` [PATCH 29/31] inferior::clear_thread_list always silent Pedro Alves
2023-06-12 12:20 ` Andrew Burgess
2022-12-12 20:31 ` [PATCH 30/31] Centralize "[Thread ...exited]" notifications Pedro Alves
2023-02-04 16:05 ` Andrew Burgess
2023-03-10 17:21 ` Pedro Alves
2023-02-16 15:40 ` Andrew Burgess
2023-06-12 12:23 ` Andrew Burgess
2022-12-12 20:31 ` [PATCH 31/31] Cancel execution command on thread exit, when stepping, nexting, etc Pedro Alves
2023-06-12 13:12 ` Andrew Burgess
2023-01-24 19:47 ` [PATCH v3 00/31] Step over thread clone and thread exit Pedro Alves
2023-11-13 14:24 ` [PATCH " Pedro Alves
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