RE: [PATCH 3/3] gdb: add assertion when marking the remote async flag

["Terekhov, Mikhail" <Mikhail.Terekhov@dell.com>]

> -----Original Message-----
> From: Gdb-patches <gdb-patches-
> bounces+mikhail.terekhov=dell.com@sourceware.org> On Behalf Of Simon
> Marchi via Gdb-patches
> Sent: Tuesday, October 3, 2023 10:04 PM
> To: gdb-patches@sourceware.org
> Cc: Simon Marchi <simon.marchi@efficios.com>
> Subject: [PATCH 3/3] gdb: add assertion when marking the remote async flag
>
>
> [EXTERNAL EMAIL]
>
> From: Simon Marchi <simon.marchi@efficios.com>
>
> As reported in bug 30630 [1], we hit a case where the remote target's async flag
> is marked while the target is not configured (yet) to work async.  This should not
> happen.  It is caught thanks to this assert in
> remote_target::wait:
>
>     /* Start by clearing the flag that asks for our wait method to be called,
>        we'll mark it again at the end if needed.  If the target is not in
>        async mode then the async token should not be marked.  */
>     if (target_is_async_p ())
>       rs->clear_async_event_handler ();
>     else
>       gdb_assert (!rs->async_event_handler_marked ());
>
> This is helpful, but I think that we could have caught the problem earlier than
> that, at the moment we marked the handler.  Catching problems earlier makes
> them easier to debug.
>
> [1]
> https://urldefense.com/v3/__https://sourceware.org/bugzilla/show_bug.cgi?id
> =30630__;!!LpKI!j0fTzubsC8RVdwinGn-r82-
> mX7hLUvNffNCQWwFTCYyR9EWj0CtlY9ERyT_AXgqsNQ0ZjS4Ls53fdBnUrLhWIw
> hIBW9P$ [sourceware[.]org]
>
> Change-Id: I7e229c74b04da82bef6a817d5a676be5cf52e833
> ---
>  gdb/remote.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/remote.c b/gdb/remote.c index 38d0027dbf9e..7830b5cec33f
> 100644
> --- a/gdb/remote.c
> +++ b/gdb/remote.c
> @@ -424,7 +424,10 @@ class remote_state
>    }
>
>    void mark_async_event_handler ()
> -  { ::mark_async_event_handler (m_async_event_handler_token); }
> +  {
> +    gdb_assert (this->is_async_p ());
> +    ::mark_async_event_handler (m_async_event_handler_token);  }

This change made the need for fix suggested in [1] more obvious.
The assert in mark_async_event_handler () is stronger than check in
remote_target::queued_stop_reply().
I.e. mark_async_event_handler () should not be called in
remote_target::queued_stop_reply() unless async_handler != NULL i.e.
target_is_async_p() !=0.

I'd suggest to merge in fix from [1] into this series.

>
>    void clear_async_event_handler ()
>    { ::clear_async_event_handler (m_async_event_handler_token); }
> --
> 2.42.0


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