From: Andrew Burgess <aburgess@redhat.com>
To: Patrick Monnerat <patrick@monnerat.net>, gdb-patches@sourceware.org
Subject: Re: [PATCH] Add a timeout parameter to gdb_do_one_event
Date: Thu, 18 Aug 2022 12:16:51 +0100 [thread overview]
Message-ID: <87tu69ajj0.fsf@redhat.com> (raw)
In-Reply-To: <20220317130846.162955-1-patrick@monnerat.net>
Patrick Monnerat via Gdb-patches <gdb-patches@sourceware.org> writes:
> Since commit b2d8657, having a per-interpreter event/command loop is not
> possible anymore.
>
> As Insight uses a GUI that has its own event loop, gdb and GUI event
> loops have then to be "merged" (i.e.: work together). But this is
> problematic as gdb_do_one_event is not aware of this alternate event
> loop and thus may wait forever.
>
> The solution is to implement a wait timeout to gdb_do_one_event. This
> cannot be done externally as gdb timers are event sources themselves.
>
> The new parameter defaults to "no timeout": as it is used by Insight
> only, there is no need to update calls from the gdb source tree.
> ---
> gdbsupport/event-loop.cc | 45 +++++++++++++++++++++++++++++++---------
> gdbsupport/event-loop.h | 2 +-
> 2 files changed, 36 insertions(+), 11 deletions(-)
>
> diff --git a/gdbsupport/event-loop.cc b/gdbsupport/event-loop.cc
> index 385b45b2de1..14168cae5a6 100644
> --- a/gdbsupport/event-loop.cc
> +++ b/gdbsupport/event-loop.cc
> @@ -33,6 +33,8 @@
> #include <sys/types.h>
> #include "gdbsupport/gdb_sys_time.h"
> #include "gdbsupport/gdb_select.h"
> +#include "gdbsupport/gdb_optional.h"
> +#include "gdbsupport/scope-exit.h"
>
> /* See event-loop.h. */
>
> @@ -177,12 +179,17 @@ static int update_wait_timeout (void);
> static int poll_timers (void);
> \f
> /* Process one high level event. If nothing is ready at this time,
> - wait for something to happen (via gdb_wait_for_event), then process
> - it. Returns >0 if something was done otherwise returns <0 (this
> - can happen if there are no event sources to wait for). */
> + wait at most MSTIMEOUT milliseconds for something to happen (via
> + gdb_wait_for_event), then process it. Returns >0 if something was
> + done, <0 if there are no event sources to wait for, =0 if timeout occurred.
> + A timeout of 0 allows to serve an already pending event, but does not
> + wait if none found.
> + Setting the timeout to a negative value disables it.
> + The timeout is never used by gdb itself, it is however needed to
> + integrate gdb event handling within Insight's GUI event loop. */
>
> int
> -gdb_do_one_event (void)
> +gdb_do_one_event (int mstimeout)
> {
> static int event_source_head = 0;
> const int number_of_sources = 3;
> @@ -229,17 +236,35 @@ gdb_do_one_event (void)
> return 1;
> }
>
> + if (!mstimeout)
> + return 0; /* Null timeout: do not wait for an event. */
> +
This should be:
if (mstimeout == 0)
As mstimeout is an int, not a bool.
> /* Block waiting for a new event. If gdb_wait_for_event returns -1,
> we should get out because this means that there are no event
> sources left. This will make the event loop stop, and the
> - application exit. */
> + application exit.
> + If a timeout has been given, a new timer is set accordingly
> + to abort event wait. It is deleted upon gdb_wait_for_event
> + termination and thus should never be triggered.
> + When the timeout is reached, events are not monitored again:
> + they already have been checked in the loop above. */
>
> - if (gdb_wait_for_event (1) < 0)
> - return -1;
> + gdb::optional<int> timer_id;
>
> - /* If gdb_wait_for_event has returned 1, it means that one event has
> - been handled. We break out of the loop. */
> - return 1;
> + SCOPE_EXIT
> + {
> + if (timer_id.has_value ())
> + delete_timer (*timer_id);
> + };
> +
> + if (mstimeout > 0)
> + timer_id = create_timer (mstimeout,
> + [] (gdb_client_data arg)
> + {
> + ((gdb::optional<int> *) arg)->reset ();
> + },
> + &timer_id);
> + return gdb_wait_for_event (1);
More just a warning really, but this isn't going to work in all cases.
If a target doesn't support async-mode then GDB will block waiting for
events in the check_async_event_handlers call above, and never gets down
this far.
I'm interested in this because I also want to have the event loop run
under a timeout for a patch I'm working on, and everything works fine
except for the case when I run with async support disabled.
I'm currently investigating having non-async targets ask the event loop
for a maximum wait time before they block, then return to the event loop
in order to check timers.
If I can get this working, I'll want to move your create_timer call to
the start of gdb_do_one_event, so that the timer is in place before the
call to check_async_event_handlers - though I'm not quite sure how this
would be expected to interact with the case where 'mstimeout == 0'.
Thanks,
Andrew
> }
>
> /* See event-loop.h */
> diff --git a/gdbsupport/event-loop.h b/gdbsupport/event-loop.h
> index 9ed592877ab..c82493e9bdf 100644
> --- a/gdbsupport/event-loop.h
> +++ b/gdbsupport/event-loop.h
> @@ -76,7 +76,7 @@ typedef void (timer_handler_func) (gdb_client_data);
>
> /* Exported functions from event-loop.c */
>
> -extern int gdb_do_one_event (void);
> +extern int gdb_do_one_event (int mstimeout = -1);
> extern void delete_file_handler (int fd);
>
> /* Add a file handler/descriptor to the list of descriptors we are
> --
> 2.35.1
next prev parent reply other threads:[~2022-08-18 11:16 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-17 13:08 Patrick Monnerat
2022-04-15 16:21 ` Tom Tromey
2022-04-16 0:38 ` Patrick Monnerat
2022-07-22 13:41 ` Simon Marchi
2022-07-22 22:45 ` Patrick Monnerat
2022-07-25 1:07 ` Simon Marchi
2022-08-18 11:16 ` Andrew Burgess [this message]
2022-08-19 11:29 ` Patrick Monnerat
2022-08-23 18:38 ` Tom Tromey
-- strict thread matches above, loose matches on Subject: below --
2022-03-14 14:49 Patrick Monnerat
2022-03-14 16:17 ` Pedro Alves
2021-08-26 18:30 Patrick Monnerat
2021-08-23 18:23 Patrick Monnerat
2021-08-26 3:24 ` Simon Marchi
2021-08-26 11:36 ` Patrick Monnerat
2021-08-26 13:47 ` Simon Marchi
2021-08-26 15:14 ` Patrick Monnerat
2021-08-27 18:08 ` Tom Tromey
2021-08-28 0:07 ` Patrick Monnerat
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