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Rozycki" , Andrew Burgess Subject: [PATCH v2 1/6] sim: Allow an overdue event to be descheduled Date: Fri, 21 Aug 2026 05:22:59 +0200 Message-ID: <20260821032304.293603-2-sebastian.huber@embedded-brains.de> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260821032304.293603-1-sebastian.huber@embedded-brains.de> References: <20260821032304.293603-1-sebastian.huber@embedded-brains.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-DKIM-Status: pass [(embedded-brains.de) - 78.47.166.52] X-Virus-Scanned: Clear (ClamAV 1.4.3/28098/Thu Aug 20 08:24:22 2026) 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 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. Approved-By: Andrew Burgess --- 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..e832992c266 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 !=3D NULL) ? dead->trace : "")); sim_events_free (sd, dead); update_time_from_event (sd); - SIM_ASSERT ((events->time_from_event >=3D 0) =3D=3D (events->queu= e !=3D NULL)); + /* sim_events_slip() advances the time past an event + which is still queued. The head of the queue is then + overdue rather than pending. */ + SIM_ASSERT (events->queue !=3D NULL + || events->time_from_event < 0); return; } } --=20 2.51.0