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Re: problem with new vforkdone stop reply in 7.10
- From: Don Breazeal <donb at codesourcery dot com>
- To: Pedro Alves <palves at redhat dot com>
- Cc: "gdb at sourceware dot org" <gdb at sourceware dot org>
- Date: Tue, 15 Sep 2015 07:51:25 -0700
- Subject: Re: problem with new vforkdone stop reply in 7.10
- Authentication-results: sourceware.org; auth=none
- References: <55F828D9 dot 8050100 at redhat dot com>
On 9/15/2015 7:19 AM, 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:
>
> @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 if you next
> a T05vforkdone, how can we tell which of the parent processes
> has had its child exit/exec?
>
> Thanks,
> Pedro Alves
>
Hi Pedro,
Thanks for pointing this out. I will take a look at it. This case
would make an interesting test.
--Don