On 2020-12-07 15:29:50 [+0100], Thomas Gleixner wrote: > On Mon, Dec 07 2020 at 14:07, Sebastian Andrzej Siewior wrote: > > One thing I noticed while testing it is that the "corner" case in > > timer_sync_wait_running() is quite reliably hit by rcu_preempt > > rcu_gp_fqs_loop() -> swait_event_idle_timeout_exclusive() invocation. > > I assume it's something like this: > > timeout -> wakeup > > ->preemption > del_timer_sync() > .....
Yes, but it triggers frequently. Like `rcuc' is somehow is aligned with the timeout. | <idle>-0 [007] dN.h4.. 46.299705: sched_wakeup: comm=rcuc/7 pid=53 prio=98 target_cpu=007 | <idle>-0 [007] d...2.. 46.299728: sched_switch: prev_comm=swapper/7 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=rcuc/7 next_pid=53 next_prio=98 | rcuc/7-53 [007] d...2.. 46.299742: sched_switch: prev_comm=rcuc/7 prev_pid=53 prev_prio=98 prev_state=S ==> next_comm=ksoftirqd/7 next_pid=54 next_prio=120 | ksoftirqd/7-54 [007] .....13 46.299750: timer_expire_entry: timer=000000003bd1e045 function=process_timeout now=4294903802 baseclk=4294903802 | ksoftirqd/7-54 [007] d...213 46.299750: sched_waking: comm=rcu_preempt pid=11 prio=98 target_cpu=007 | ksoftirqd/7-54 [007] dN..313 46.299754: sched_wakeup: comm=rcu_preempt pid=11 prio=98 target_cpu=007 | ksoftirqd/7-54 [007] dN..213 46.299756: sched_stat_runtime: comm=ksoftirqd/7 pid=54 runtime=13265 [ns] vruntime=3012610540 [ns] | ksoftirqd/7-54 [007] d...213 46.299760: sched_switch: prev_comm=ksoftirqd/7 prev_pid=54 prev_prio=120 prev_state=R+ ==> next_comm=rcu_preempt next_pid=11 next_prio=98 | rcu_preempt-11 [007] d...311 46.299766: sched_pi_setprio: comm=ksoftirqd/7 pid=54 oldprio=120 newprio=98 del_timer_sync() | rcu_preempt-11 [007] d...211 46.299773: sched_switch: prev_comm=rcu_preempt prev_pid=11 prev_prio=98 prev_state=R+ ==> next_comm=ksoftirqd/7 next_pid=54 next_prio=98 | ksoftirqd/7-54 [007] .....13 46.299774: timer_expire_exit: timer=000000003bd1e045 | ksoftirqd/7-54 [007] dN..311 46.299784: sched_pi_setprio: comm=ksoftirqd/7 pid=54 oldprio=98 newprio=120 | ksoftirqd/7-54 [007] dN..311 46.299788: sched_waking: comm=rcu_preempt pid=11 prio=98 target_cpu=007 | ksoftirqd/7-54 [007] dN..411 46.299790: sched_wakeup: comm=rcu_preempt pid=11 prio=98 target_cpu=007 | ksoftirqd/7-54 [007] dN..311 46.299792: sched_stat_runtime: comm=ksoftirqd/7 pid=54 runtime=7404 [ns] vruntime=3012617944 [ns] | ksoftirqd/7-54 [007] d...2.. 46.299797: sched_switch: prev_comm=ksoftirqd/7 prev_pid=54 prev_prio=120 prev_state=S ==> next_comm=rcu_preempt next_pid=11 next_prio=98 > Thanks, > > tglx Sebastian
