[review] [gdb/threads] Fix hang in stop_all_threads after killing inferior

["Tom de Vries (Code Review)" <gerrit at gnutoolchain-gerrit dot osci dot io>]

Tom de Vries has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/759
......................................................................


Patch Set 1:

> FWIW, I looked over the review comments there, and noticed the suggestion to "leave the TARGET_WAITKIND_EXITED/TARGET_WAITKIND_SIGNALLED event pending", which I tried using this additional patch:
> ...
> diff --git a/gdb/infrun.c b/gdb/infrun.c
> index e34ddc83b45..c1035c25d7f 100644
> --- a/gdb/infrun.c
> +++ b/gdb/infrun.c
> @@ -4774,7 +4774,11 @@ stop_all_threads (void)
>  
>           if (event.ws.kind == TARGET_WAITKIND_SIGNALLED
>               && event.ws.value.sig == GDB_SIGNAL_KILL)
> -           goto done;
> +           {
> +             thread_info *t = find_thread_ptid (event.target, event.ptid);
> +             save_waitstatus (t, &event.ws);
> +             goto done;
> +           }
>           else if (event.ws.kind == TARGET_WAITKIND_NO_RESUMED
>               || event.ws.kind == TARGET_WAITKIND_THREAD_EXITED
>               || event.ws.kind == TARGET_WAITKIND_EXITED
> ...
> 
> But I didn't notice any difference in behaviour.

I've realized from another use of save_waitstatus that I have to set t->resumed in order to have the saved wait status noticed.

With this additional patch, I did manage to observe a difference in behaviour:
...
@@ -4777,6 +4777,7 @@ stop_all_threads (void)
            {
              thread_info *t = find_thread_ptid (event.target, event.ptid);
              save_waitstatus (t, &event.ws);
+             t->resumed = 1;
              goto done;
            }
          else if (event.ws.kind == TARGET_WAITKIND_NO_RESUMED
...

The difference is in what happens when I continue after the ^C is handled:
- without the two patches gdb hangs, until I press enter, after which I get the
  prompt
- with the two patches, gdb just presents the prompt


-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: Ibe1f29251fe2ff1c1991f041babbe18373c113b1
Gerrit-Change-Number: 759
Gerrit-PatchSet: 1
Gerrit-Owner: Tom de Vries <tdevries@suse.de>
Gerrit-Reviewer: Pedro Alves <palves@redhat.com>
Gerrit-Reviewer: Tom de Vries <tdevries@suse.de>
Gerrit-CC: Mihails Strasuns <mihails.strasuns@intel.com>
Gerrit-CC: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Gerrit-Comment-Date: Thu, 30 Jan 2020 14:52:10 +0000
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Gerrit-MessageType: comment