Re: [PATCH][gdb] Fix assert in remote_async_get_pending_events_handler

[Andrew Burgess <andrew.burgess@embecosm.com>]

* Tom de Vries <tdevries@suse.de> [2021-04-22 10:51:29 +0200]:

> Hi,
> 
> Occassionally I run into the following assert:
> ...
> (gdb) PASS: gdb.multi/multi-target-continue.exp: inferior 5
> Remote debugging from host ::1, port 49990^M
> Process multi-target-continue created; pid = 31241^M
> src/gdb/remote-notif.c:113: internal-error: \
>   void remote_async_get_pending_events_handler(gdb_client_data): \
>   Assertion `target_is_non_stop_p ()' failed.^M
> ...
> 
> The assert checks target_is_non_stop_p, which is related to the current
> target.
> 
> Fix this by changing the assert such that it checks non-stopness related to
> the event it's handling.
> 
> Tested on x86_64-linux.
> 
> Any comments?

This seems fine to me.  I wonder though if you considered converting
target_is_non_stop_p into a member function on target_ops?  If we did
then we would avoid having to switch targets just to ask this
question.  All of the helper functions that target_is_non_stop_p calls
are already available as member functions so there would be no
additional changes needed I think.

Just a thought.

Thanks,
Andrew

> 
> Thanks,
> - Tom
> 
> [gdb] Fix assert in remote_async_get_pending_events_handler
> 
> 2021-04-16  Simon Marchi  <simon.marchi@polymtl.ca>
> 	    Tom de Vries  <tdevries@suse.de>
> 
> 	PR remote/27710
> 	* remote.c (remote_target_is_non_stop_p): New function.
> 	* remote.h (remote_target_is_non_stop_p): Declare.
> 	* remote-notif.c (remote_async_get_pending_events_handler): Fix assert
> 	to check non-stopness using notif_state->remote rather current target.
> 
> ---
>  gdb/remote-notif.c |  2 +-
>  gdb/remote.c       | 11 +++++++++++
>  gdb/remote.h       |  1 +
>  3 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/gdb/remote-notif.c b/gdb/remote-notif.c
> index 5a3e1395b76..4245015ae37 100644
> --- a/gdb/remote-notif.c
> +++ b/gdb/remote-notif.c
> @@ -110,7 +110,7 @@ remote_async_get_pending_events_handler (gdb_client_data data)
>  {
>    remote_notif_state *notif_state = (remote_notif_state *) data;
>    clear_async_event_handler (notif_state->get_pending_events_token);
> -  gdb_assert (target_is_non_stop_p ());
> +  gdb_assert (remote_target_is_non_stop_p (notif_state->remote));
>    remote_notif_process (notif_state, NULL);
>  }
>  
> diff --git a/gdb/remote.c b/gdb/remote.c
> index 7429e1a86b3..2e365df9bba 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -14730,6 +14730,17 @@ remote_target::store_memtags (CORE_ADDR address, size_t len,
>    return packet_check_result (rs->buf.data ()) == PACKET_OK;
>  }
>  
> +/* Return true if remote target T is non-stop.  */
> +
> +bool
> +remote_target_is_non_stop_p (remote_target *t)
> +{
> +  scoped_restore_current_thread restore_thread;
> +  switch_to_target_no_thread (t);
> +
> +  return target_is_non_stop_p ();
> +}
> +
>  #if GDB_SELF_TEST
>  
>  namespace selftests {
> diff --git a/gdb/remote.h b/gdb/remote.h
> index 18352ddb866..46bfa01fc79 100644
> --- a/gdb/remote.h
> +++ b/gdb/remote.h
> @@ -77,4 +77,5 @@ extern int remote_register_number_and_offset (struct gdbarch *gdbarch,
>  
>  extern void remote_notif_get_pending_events (remote_target *remote,
>  					     struct notif_client *np);
> +extern bool remote_target_is_non_stop_p (remote_target *t);
>  #endif