On 2024-08-20 15:13, Pavel Begunkov wrote: >>>>> On 8/20/24 2:08 PM, David Wei wrote: >>>> To rephase the question, why is the original code calling >>>> schedule_hrtimeout_range_clock() not needing to differentiate behaviour >>>> between defer taskrun and not? >>> >>> Because that part is the same, the task schedules out and goes to sleep. >>> That has always been the same regardless of how the ring is setup. Only >>> difference is that DEFER_TASKRUN doesn't add itself to ctx->wait, and >>> hence cannot be woken by a wake_up(ctx->wait). We have to wake the task >>> manually. >>> >> >> io_cqring_timer_wakeup() is the timer expired callback which calls >> wake_up_process() or io_cqring_wake() depending on DEFER_TASKRUN. >> >> The original code calling schedule_hrtimeout_range_clock() uses >> hrtimer_sleeper instead, which has a default timer expired callback set >> to hrtimer_wakeup(). >> >> hrtimer_wakeup() only calls wake_up_process(). >> >> My question is: why this asymmetry? Why does the new custom callback >> require io_cqring_wake()? > > That's what I'm saying, it doesn't need and doesn't really want it. > From the correctness point of view, it's ok since we wake up a > (unnecessarily) larger set of tasks. > Yeah your explanation that came in while I was writing the email answered it, thanks Pavel.
