Re: problem with new vforkdone stop reply in 7.10

[Pedro Alves <palves@redhat.com>]

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.

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.

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.

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;
-- 
1.9.3