[review v2] infrun: handle already-exited threads when attempting to stop

["Tankut Baris Aktemur (Code Review)" <gerrit@gnutoolchain-gerrit.osci.io>]

Tankut Baris Aktemur has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/133
......................................................................


Patch Set 2:

(1 comment)

| --- gdb/infrun.c
| +++ gdb/infrun.c
| @@ -4494,7 +4509,19 @@ stop_all_threads (void)
| +		  if (ws.kind == TARGET_WAITKIND_THREAD_EXITED)
| +		    delete_thread (t);
| +		  else
| +		    {
| +		      /* TARGET_WAITKIND_EXITED or
| +			 TARGET_WAITKIND_SIGNALLED.  */
| +		      /* Need to restore the context because
| +			 handle_inferior_exit switches it.  */
| +		      scoped_restore_current_pspace_and_thread restore;
| +		      handle_inferior_exit (event_ptid, ws);

PS2, Line 4518:

> > The fix for this I think must be around leaving the TARGET_WAITKIND_EXITED/TARGET_WAITKIND_SIGNALLED
> event pending, so that it is processed later when we're out of the stop_all_threads loop and back to
> dequeuing the next event.
> 
> 
> I'd like to ask for your opinion on making the second exit event pending.
> One problem is, because the event has not been reported to the user yet,
> the user still thinks that the inferior is alive.  So, after getting the
> prompt because of the first exit event, they may be tempted to do "info
> threads" or switch to the not-yet-reported-inferior and inspect its state.  
> This triggers a query (e.g. of registers) on the process that is already 
> gone.  I tried the following scenario with the current master branch
> (the patch that I proposed was not applied):

Kindly pinging.

Thanks,

-Baris

| +		    }
| +		}
|  	    }
|  	  else
|  	    {
|  	      thread_info *t = find_thread_ptid (event_ptid);
|  	      if (t == NULL)
|  		t = add_thread (event_ptid);
|  

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I7cec98f40283773b79255d998511da434e9cd408
Gerrit-Change-Number: 133
Gerrit-PatchSet: 2
Gerrit-Owner: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-Reviewer: Luis Machado <luis.machado@linaro.org>
Gerrit-Reviewer: Pedro Alves <palves@redhat.com>
Gerrit-Reviewer: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-Comment-Date: Wed, 08 Jan 2020 15:57:35 +0000
Gerrit-HasComments: Yes
Gerrit-Has-Labels: No
Comment-In-Reply-To: Pedro Alves <palves@redhat.com>
Comment-In-Reply-To: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-MessageType: comment