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[87.115.72.67]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-482a5b81715sm10868990f8f.35.2026.08.18.02.59.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Aug 2026 02:59:10 -0700 (PDT) From: Andrew Burgess To: Sebastian Huber , gdb-patches@sourceware.org Subject: Re: [PATCH 1/4] sim: Allow an overdue event to be descheduled In-Reply-To: <20260816234357.278358-2-sebastian.huber@embedded-brains.de> References: <20260816234357.278358-1-sebastian.huber@embedded-brains.de> <20260816234357.278358-2-sebastian.huber@embedded-brains.de> Date: Tue, 18 Aug 2026 10:59:10 +0100 Message-ID: <87zeyj21ht.fsf@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: REc2TVUdWaUnsRmp3JwGw4OacsUFTBchjYiDpAzp1_I_1787047152 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces~public-inbox=simark.ca@sourceware.org Sebastian Huber writes: > sim_events_deschedule() asserted that a non-empty event queue implies a > non-negative time from event. That is not an invariant. > sim_events_slip() decrements the time from event unconditionally, so the > time can pass an event which is still queued. update_time_from_event() > then computes a negative time from event for the head of the queue, > which is overdue rather than pending. The next tick raises the pending > work flag and sim_events_process() consumes it, so nothing is lost. > > An event handler which deschedules another overdue event triggers the > assertion. The MIPS jmr3904 board reaches this with two timers running: > they queue events for the same time, a branch delay slot slips the time > past both, and the handler of the first deschedules the second. > > Assert only the direction which holds: an empty queue gives a negative > time from event. > > Signed-off-by: Sebastian Huber > --- > sim/common/sim-events.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/sim/common/sim-events.c b/sim/common/sim-events.c > index f87f133efc3..e908c40f764 100644 > --- a/sim/common/sim-events.c > +++ b/sim/common/sim-events.c > @@ -852,7 +852,11 @@ sim_events_deschedule (SIM_DESC sd, > (dead->trace != NULL) ? dead->trace : "")); > sim_events_free (sd, dead); > update_time_from_event (sd); > - SIM_ASSERT ((events->time_from_event >= 0) == (events->queue != NULL)); > + /* sim_events_slip() advances the time past an event > + which is still queued. The head of the queue is then Two spaces after the period please. With that fixed: Approved-By: Andrew Burgess Thanks, Andrew > + overdue rather than pending. */ > + SIM_ASSERT (events->queue != NULL > + || events->time_from_event < 0); > return; > } > } > -- > 2.51.0