Richard Henderson <richard.hender...@linaro.org> writes: > On 2/7/25 07:45, Peter Maydell wrote: >> This is where things go wrong -- icount_start_warp_timer() >> notices that all CPU threads are currently idle, and >> decides it needs to warp the timer forwards to the >> next deadline, which is at the end of time -- INT64_MAX. >> But once timer_mod_ns() returns, the generic timer code >> is going to raise an interrupt (this goes through the GIC >> code and comes back into the CPU which calls cpu_interrupt()), >> so we don't want to warp the timer at all. The clock should >> stay exactly at the value it has and the CPU is going to >> have more work to do. >> How is this supposed to work? Shouldn't we only be doing >> the "start moving the icount forward to the next deadline" >> once we've completed all the "run timers and AIO stuff" that >> icount_handle_deadline() triggers, not randomly in the middle >> of that when this timer callback or some other one might do >> something to trigger an interrupt? > > I don't understand timer warping at all. And you're right, it doesn't > seem like this should happen outside of a specific point in the main > loop.
This has come up before - and the conclusion was we don't know what sleep=on/off is meant to mean. If the processor is asleep and there are no timers to fire then nothing will happen. It was off-list though: Subject: Re: qemu-system-aarch64 & icount behavior Date: Wed, 22 Jul 2020 at 11:21 From: Kumar Gala <kumar.g...@linaro.org> Subject: Fwd: qemu-system-aarch64 & icount behavior Message-ID: <cafeaca9dnbqfnoc1hjav2dylwsqu+yye5ryzp5wrlxyc1gz...@mail.gmail.com> Date: Fri, 24 Jul 2020 17:25:51 +0100 From: Peter Maydell <peter.mayd...@linaro.org> >> ... But I don't think there's any reason why >> timer callbacks should be obliged to reprogram their timers >> last, and in any case you can imagine scenarios where there >> are multiple timer callbacks for different timers and it's >> only the second timer that raises an interrupt... > > Agreed. > > > r~ -- Alex Bennée Virtualisation Tech Lead @ Linaro
