On 16.01.2019 07:24, Frederic Weisbecker wrote: > On Fri, Dec 28, 2018 at 12:11:12AM +0100, Heiner Kallweit wrote: >> >> # tracer: nop >> # >> # _-----=> irqs-off >> # / _----=> need-resched >> # | / _---=> hardirq/softirq >> # || / _--=> preempt-depth >> # ||| / delay >> # TASK-PID CPU# |||| TIMESTAMP FUNCTION >> # | | | |||| | | >> <idle>-0 [001] d.h2 1479.099092: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.099098: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.099106: softirq_raise: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.099114: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.099120: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.099121: softirq_entry: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.099134: softirq_exit: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.099135: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.099141: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.100094: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.100109: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.100116: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.101091: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.101113: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.101118: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.102094: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.102114: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.102121: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.103091: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.103097: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.103105: softirq_raise: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.103114: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.103118: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.103119: softirq_entry: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.103131: softirq_exit: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.103132: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.103138: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.105092: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.105115: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.105119: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.106092: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.106112: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] .Ns2 1479.106144: softirq_exit: vec=9 >> [action=RCU] >> cpuhp/1-13 [001] d..2 1479.106279: timer_cancel: >> timer=0000000009a25653 >> <idle>-0 [001] d.h2 1479.106965: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.106969: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.106974: softirq_raise: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.106981: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.106984: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.106985: softirq_entry: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.106994: softirq_exit: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.106995: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.106999: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.107996: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.108010: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.108014: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.109009: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.109013: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.109024: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.109028: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.109028: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.109033: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.110013: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.110033: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] ..s2 1479.110040: softirq_exit: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.111011: softirq_raise: vec=1 >> [action=TIMER] >> <idle>-0 [001] d.h2 1479.111017: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] d.h2 1479.111026: softirq_raise: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.111035: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.111040: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] ..s2 1479.111040: softirq_entry: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.111052: softirq_exit: vec=7 >> [action=SCHED] >> <idle>-0 [001] ..s2 1479.111052: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] .Ns2 1479.111079: softirq_exit: vec=9 >> [action=RCU] >> cpuhp/1-13 [001] dNh2 1479.112930: softirq_raise: vec=1 >> [action=TIMER] >> cpuhp/1-13 [001] dNh2 1479.112935: softirq_raise: vec=9 >> [action=RCU] >> <idle>-0 [001] d..1 1479.113077: <stack trace> >> => can_stop_idle_tick.isra.14 >> => tick_nohz_get_sleep_length >> => menu_select >> => cpuidle_select >> => do_idle >> => cpu_startup_entry >> => start_secondary >> => secondary_startup_64 >> <idle>-0 [001] .Ns2 1479.113110: softirq_entry: vec=1 >> [action=TIMER] >> <idle>-0 [001] .Ns2 1479.113114: softirq_exit: vec=1 >> [action=TIMER] >> <idle>-0 [001] .Ns2 1479.113115: softirq_entry: vec=9 >> [action=RCU] >> <idle>-0 [001] .Ns2 1479.113139: softirq_exit: vec=9 >> [action=RCU] > > > So, I'm being very doubtful now actually. > > First of all, I realize my patch only fixes things halfway. Only softirq > raised from > hardirqs are going to be handled after ksoftirqd is parked. If it's raised > outside > interrupts, the softirq is going to be ignored. If other smpboot kthreads, > following > ksoftirqd parking, raise softirqs from their park() callback we should at > least warn > that we are ignoring that. > > Also, I'm still not sure if you're running threaded IRQs. Very likely not as > the softirqs in your traces are executed in idle, which means from an IRQ > interrupting > idle. You haven't passed "threadirqs" in your kernel parameters, right? > In any case we need to figure out why your softirqs raised at 1479.112930 and > 1479.112935 don't get handled. > The only softirq I'm aware of is network NAPI processing. And no, I have no kernel command line parameter "threadirqs" set.
> Finally I don't understand why you have so many timer softirqs and yet no > timer traces > at all, I turned them on in the script I gave you. So something weird is > happening with > the timers code. At best we are wasting lots of CPU cycles with those empty > softirqs, at > worst we are miscalculating some expiration somewhere, possibly ignoring a > timer. > > So I'll need to cook up an updated debug patch for you to trigger if you don't > mind. > I don't mind .. > Thanks. > Heiner
