Re: [PATCH 18/31] Implement GDB_THREAD_OPTION_EXIT support for Linux GDBserver

[Andrew Burgess <aburgess@redhat.com>]

Pedro Alves <pedro@palves.net> writes:

> This implements support for the new GDB_THREAD_OPTION_EXIT thread
> option for Linux GDBserver.

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew


>
> Change-Id: I96b719fdf7fee94709e98bb3a90751d8134f3a38
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338
> ---
>  gdbserver/linux-low.cc | 38 +++++++++++++++++++++++++-------------
>  gdbserver/linux-low.h  |  9 +++++----
>  2 files changed, 30 insertions(+), 17 deletions(-)
>
> diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
> index 8c0d3103398..ebc3bf34127 100644
> --- a/gdbserver/linux-low.cc
> +++ b/gdbserver/linux-low.cc
> @@ -144,6 +144,18 @@ is_leader (thread_info *thread)
>    return ptid.pid () == ptid.lwp ();
>  }
>  
> +/* Return true if we should report thread exit events to GDB, for
> +   THR.  */
> +
> +static bool
> +report_exit_events_for (thread_info *thr)
> +{
> +  client_state &cs = get_client_state ();
> +
> +  return (cs.report_thread_events
> +	  || (thr->thread_options & GDB_THREAD_OPTION_EXIT) != 0);
> +}
> +
>  /* LWP accessors.  */
>  
>  /* See nat/linux-nat.h.  */
> @@ -2230,7 +2242,6 @@ linux_low_ptrace_options (int attached)
>  void
>  linux_process_target::filter_event (int lwpid, int wstat)
>  {
> -  client_state &cs = get_client_state ();
>    struct lwp_info *child;
>    struct thread_info *thread;
>    int have_stop_pc = 0;
> @@ -2317,7 +2328,7 @@ linux_process_target::filter_event (int lwpid, int wstat)
>        /* If this is not the leader LWP, then the exit signal was not
>  	 the end of the debugged application and should be ignored,
>  	 unless GDB wants to hear about thread exits.  */
> -      if (cs.report_thread_events || is_leader (thread))
> +      if (report_exit_events_for (thread) || is_leader (thread))
>  	{
>  	  /* Since events are serialized to GDB core, and we can't
>  	     report this one right now.  Leave the status pending for
> @@ -2879,13 +2890,20 @@ ptid_t
>  linux_process_target::filter_exit_event (lwp_info *event_child,
>  					 target_waitstatus *ourstatus)
>  {
> -  client_state &cs = get_client_state ();
>    struct thread_info *thread = get_lwp_thread (event_child);
>    ptid_t ptid = ptid_of (thread);
>  
> +  /* Note we must filter TARGET_WAITKIND_SIGNALLED as well, otherwise
> +     if a non-leader thread exits with a signal, we'd report it to the
> +     core which would interpret it as the whole-process exiting.
> +     There is no TARGET_WAITKIND_THREAD_SIGNALLED event kind.  */
> +  if (ourstatus->kind () != TARGET_WAITKIND_EXITED
> +      && ourstatus->kind () != TARGET_WAITKIND_SIGNALLED)
> +    return ptid;
> +
>    if (!is_leader (thread))
>      {
> -      if (cs.report_thread_events)
> +      if (report_exit_events_for (thread))
>  	ourstatus->set_thread_exited (0);
>        else
>  	ourstatus->set_ignore ();
> @@ -3028,10 +3046,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
>  	     WTERMSIG (w));
>  	}
>  
> -      if (ourstatus->kind () == TARGET_WAITKIND_EXITED)
> -	return filter_exit_event (event_child, ourstatus);
> -
> -      return ptid_of (current_thread);
> +      return filter_exit_event (event_child, ourstatus);
>      }
>  
>    /* If step-over executes a breakpoint instruction, in the case of a
> @@ -3600,10 +3615,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
>  			target_pid_to_str (ptid_of (current_thread)).c_str (),
>  			ourstatus->to_string ().c_str ());
>  
> -  if (ourstatus->kind () == TARGET_WAITKIND_EXITED)
> -    return filter_exit_event (event_child, ourstatus);
> -
> -  return ptid_of (current_thread);
> +  return filter_exit_event (event_child, ourstatus);
>  }
>  
>  /* Get rid of any pending event in the pipe.  */
> @@ -5909,7 +5921,7 @@ linux_process_target::supports_vfork_events ()
>  gdb_thread_options
>  linux_process_target::supported_thread_options ()
>  {
> -  return GDB_THREAD_OPTION_CLONE;
> +  return GDB_THREAD_OPTION_CLONE | GDB_THREAD_OPTION_EXIT;
>  }
>  
>  /* Check if exec events are supported.  */
> diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
> index c9f9db71e09..1c1754d2b59 100644
> --- a/gdbserver/linux-low.h
> +++ b/gdbserver/linux-low.h
> @@ -575,10 +575,11 @@ class linux_process_target : public process_stratum_target
>       exited.  */
>    void check_zombie_leaders ();
>  
> -  /* Convenience function that is called when the kernel reports an exit
> -     event.  This decides whether to report the event to GDB as a
> -     process exit event, a thread exit event, or to suppress the
> -     event.  */
> +  /* Convenience function that is called when we're about to return an
> +     event to the core.  If the event is an exit or signalled event,
> +     then this decides whether to report it as process-wide event, as
> +     a thread exit event, or to suppress it.  All other event kinds
> +     are passed through unmodified.  */
>    ptid_t filter_exit_event (lwp_info *event_child,
>  			    target_waitstatus *ourstatus);
>  
> -- 
> 2.36.0