Messages in this thread | | | Subject | Re: Fix 80d20d35af1e ("nohz: Fix local_timer_softirq_pending()") may have revealed another problem | From | Heiner Kallweit <> | Date | Fri, 28 Dec 2018 00:11:12 +0100 |
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On 27.12.2018 07:53, Frederic Weisbecker wrote: > On Mon, Oct 15, 2018 at 10:58:54PM +0200, Heiner Kallweit wrote: >> On 28.09.2018 15:18, Frederic Weisbecker wrote: >>> On Thu, Sep 27, 2018 at 06:05:46PM +0200, Thomas Gleixner wrote: >>>> On Tue, 28 Aug 2018, Frederic Weisbecker wrote: >>>>> On Fri, Aug 24, 2018 at 07:06:32PM +0200, Heiner Kallweit wrote: >>>>>> I tested it and Frederic is right, it doesn't help. Can it be somehow related to >>>>>> the cpu being brought down during suspend? Because I get the warning only during >>>>>> suspend when the cpu is inactive already (but still online). >>>>> >>>>> It's hard to tell, I haven't been able to reproduce on suspend to disk/mem. >>>>> >>>>> Does this script eventually trigger it after some time? >>>> >>>> Any update to this? >>> >>> Heiner? Can you please test the script I sent to you? >>> >>> Thanks. >>> >> Sorry, took some time .. And yes, running your script triggers the message too. >> [...] > > Sorry, I got sidetracked and almost forgot about it. > > So this is triggered by CPU hotplug. At some point the CPU has an > opportunity to go idle and for some reason the timer softirq is still > pending. We need to know which timer this is about and why the timer > softirq keeps pending. > > I'm going to need your help again. Can you please run the following (possibly > repeat until it triggers the bug) ? > > echo 1 > /sys/devices/system/cpu/cpu1/online > > # Pause and reset tracing > echo 0 > /sys/kernel/debug/tracing/tracing_on > echo > /sys/kernel/debug/tracing/trace > > # Turn on relevant events > echo 1 > /sys/kernel/debug/tracing/events/timer/timer_*/enable > echo 1 > /sys/kernel/debug/tracing/events/irq/softirq_*/enable > echo 1 > /sys/kernel/debug/tracing/tracing_on > > # Trigger > echo 0 > /sys/devices/system/cpu/cpu1/online > > echo 0 > /sys/kernel/debug/tracing/tracing_on > > And please apply the following patch before. With all that I'll have the > relevant informations stored in /sys/kernel/debug/tracing/per_cpu/cpu1/trace > Please send its content to me. Thanks! > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index 69e673b..0e57a3b 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -892,6 +892,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) > (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { > pr_warn("NOHZ: local_softirq_pending %02x\n", > (unsigned int) local_softirq_pending()); > + trace_dump_stack(0); > ratelimit++; > } > return false; > >
OK, did as you advised and here comes the trace. That's the related dmesg part:
[ 1479.025092] x86: Booting SMP configuration: [ 1479.025129] smpboot: Booting Node 0 Processor 1 APIC 0x2 [ 1479.094715] NOHZ: local_softirq_pending 202 [ 1479.096557] smpboot: CPU 1 is now offline
Hope it helps. Heiner
# 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]
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