problem with new vforkdone stop reply in 7.10
Don Breazeal
donb@codesourcery.com
Tue Sep 15 15:46:00 GMT 2015
On 9/15/2015 7:51 AM, Pedro Alves wrote:
> On 09/15/2015 03:19 PM, Pedro Alves wrote:
>> Hi Don,
>>
>> Unfortunately, I missed in review that the vforkdone stop reply
>> misses indicating the thread ID of the vfork parent which the
>> event relates to:
>
> I'm testing this. I wonder whether I'm missing some reason
> to keep the vforkdone switch case separate?
> At least foll-vfork.exp still passes.
Thanks for taking care of this. I don't think you are missing
anything. I think I just over-simplified the VFORK_DONE packet
starting in my first implementation. The changes make sense to
me. It seems like you have this covered, but let me know if I
can help at all.
>
> I should split this to a separate patch, but I also noticed that
> the TARGET_WAITKIND_EXECD handling checks multi_process instead of
> report_exec_events:
>
> - else if (status->kind == TARGET_WAITKIND_EXECD && multi_process)
> + else if (status->kind == TARGET_WAITKIND_EXECD && report_exec_events)
>
> which I think would be the check we want.
Absolutely, that should be report_exec_events. I missed making that
change from a previous version of the patchset that didn't use the
report_xxx_events variables.
>
> Thanks,
> Pedro Alves
>
> From 85989d3ce1cc931aa7025e21952136ef037388a1 Mon Sep 17 00:00:00 2001
> From: Pedro Alves <palves@redhat.com>
> Date: Tue, 15 Sep 2015 15:43:12 +0100
> Subject: [PATCH] Fix vforkdone stop reply
>
> The vforkdone stop reply misses indicating the thread ID of the vfork
> parent which the event relates to:
>
> @cindex vfork events, remote reply
> @item vfork
> The packet indicates that @code{vfork} was called, and @var{r}
> is the thread ID of the new child process. Refer to
> @ref{thread-id syntax} for the format of the @var{thread-id}
> field. This packet is only applicable to targets that support
> vfork events.
>
> @cindex vforkdone events, remote reply
> @item vforkdone
> The packet indicates that a child process created by a vfork
> has either called @code{exec} or terminated, so that the
> address spaces of the parent and child process are no longer
> shared. The @var{r} part is ignored. This packet is only
> applicable to targets that support vforkdone events.
>
> Unfortunately, this is not just a documentation issue. GDBserver
> is really not specifying the thread ID. I noticed because
> in non-stop mode, gdb complains:
>
> [Thread 6089.6089] #1 stopped.
> #0 0x0000003615a011f0 in ?? ()
> 0x0000003615a011f0 in ?? ()
> (gdb) set debug remote 1
> (gdb) c
> Continuing.
> Sending packet: $QPassSignals:e;10;14;17;1a;1b;1c;21;24;25;2c;4c;#5f...Packet received: OK
> Sending packet: $vCont;c:p17c9.17c9#88...Packet received: OK
> Notification received: Stop:T05vfork:p17ce.17ce;06:40d7ffffff7f0000;07:30d7ffffff7f0000;10:e4c9eb1536000000;thread:p17c9.17c9;core:2;
> Sending packet: $vStopped#55...Packet received: OK
> Sending packet: $D;17ce#af...Packet received: OK
> Sending packet: $vCont;c:p17c9.17c9#88...Packet received: OK
> Notification received: Stop:T05vforkdone:;
> No process or thread specified in stop reply: T05vforkdone:;
> (gdb)
>
> This is not non-stop-mode-specific, however. Consider e.g., that in
> all-stop, you may be debugging more than one process at the same time.
> You continue, and both processes vfork. So when you next get a
> T05vforkdone, there's no way to tell which of the parent processes is
> done with the vfork.
>
I've started looking at adding some tests to plug some of the gaps in
fork/exec event testing. Currently I'm looking at a test that kills the
fork parent while stopped at a fork catchpoint. It seems like I should
add non-stop cases to foll-fork.exp and foll-vfork.exp as well. And
maybe the case where there are multiple vforks in progress at the same
time, if I can come up with something that is reliable.
> gdb/ChangeLog:
> 2015-09-15 Pedro Alves <palves@redhat.com>
>
> * remote-utils.c (prepare_resume_reply): Merge
> TARGET_WAITKIND_VFORK_DONE switch case with the
> TARGET_WAITKIND_FORKED case.
>
> gdb/doc/ChangeLog:
> 2015-09-15 Pedro Alves <palves@redhat.com>
>
> * gdb.texinfo: Explain that vforkdone's 'r' part indicates the
> parent process.
> ---
> gdb/doc/gdb.texinfo | 9 +++++----
> gdb/gdbserver/remote-utils.c | 19 ++++++++-----------
> 2 files changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 395f0d4..3ac8c43 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -35498,10 +35498,11 @@ indicating support.
>
> @cindex vforkdone events, remote reply
> @item vforkdone
> -The packet indicates that a child process created by a vfork
> -has either called @code{exec} or terminated, so that the
> -address spaces of the parent and child process are no longer
> -shared. The @var{r} part is ignored. This packet is only
> +The packet indicates that a child process created by a vfork has
> +either called @code{exec} or terminated, so that the address spaces of
> +the parent and child process are no longer shared. The @var{r} part is
> +the thread ID of the parent process. Refer to @ref{thread-id syntax}
> +for the format of the @var{thread-id} field. This packet is only
> applicable to targets that support vforkdone events.
>
> This packet should not be sent by default; older @value{GDBN} versions
> diff --git a/gdb/gdbserver/remote-utils.c b/gdb/gdbserver/remote-utils.c
> index ac86dd5..7cf66cc 100644
> --- a/gdb/gdbserver/remote-utils.c
> +++ b/gdb/gdbserver/remote-utils.c
> @@ -1117,6 +1117,7 @@ prepare_resume_reply (char *buf, ptid_t ptid,
> case TARGET_WAITKIND_STOPPED:
> case TARGET_WAITKIND_FORKED:
> case TARGET_WAITKIND_VFORKED:
> + case TARGET_WAITKIND_VFORK_DONE:
> case TARGET_WAITKIND_EXECD:
> {
> struct thread_info *saved_thread;
> @@ -1135,7 +1136,13 @@ prepare_resume_reply (char *buf, ptid_t ptid,
> buf = write_ptid (buf, status->value.related_pid);
> strcat (buf, ";");
> }
> - else if (status->kind == TARGET_WAITKIND_EXECD && multi_process)
> + else if (status->kind == TARGET_WAITKIND_VFORK_DONE && report_vfork_events)
> + {
> + enum gdb_signal signal = GDB_SIGNAL_TRAP;
> +
> + sprintf (buf, "T%02xvforkdone:;", signal);
> + }
> + else if (status->kind == TARGET_WAITKIND_EXECD && report_exec_events)
> {
> enum gdb_signal signal = GDB_SIGNAL_TRAP;
> const char *event = "exec";
> @@ -1269,16 +1276,6 @@ prepare_resume_reply (char *buf, ptid_t ptid,
> else
> sprintf (buf, "X%02x", status->value.sig);
> break;
> - case TARGET_WAITKIND_VFORK_DONE:
> - if (report_vfork_events)
> - {
> - enum gdb_signal signal = GDB_SIGNAL_TRAP;
> -
> - sprintf (buf, "T%02xvforkdone:;", signal);
> - }
> - else
> - sprintf (buf, "T%02x", GDB_SIGNAL_0);
> - break;
> default:
> error ("unhandled waitkind");
> break;
>
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