Re: problem with new vforkdone stop reply in 7.10

[Don Breazeal <donb at codesourcery dot com>]

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;
>