On Fri, Jun 26, 2020 at 02:05:06PM -0700, Paul E. McKenney wrote: > Currently, can_stop_idle_tick() prints "NOHZ: local_softirq_pending HH" > (where "HH" is the hexadecimal softirq vector number) when one or more > non-RCU softirq handlers are still enablded when checking to stop the > scheduler-tick interrupt. This message is not as enlightening as one > might hope, so this commit changes it to "NOHZ tick-stop error: Non-RCU > local softirq work is pending, handler #HH. > > Reported-by: Andy Lutomirski <[email protected]> > Signed-off-by: Paul E. McKenney <[email protected]>
CPU hotplug will sometimes trigger this warning on linux-next from NUMA bare-metal which the commit makes it feel more like errors. [ 267.734981] smpboot: CPU 42 is now offline [ 267.991940] smpboot: Booting Node 2 Processor 42 APIC 0x29 [ 267.998370] numa_add_cpu cpu 42 node 2: mask now 8-11,40-43 [ 268.092380] ACPI: \_SB_.SCK0.C015: Found 2 idle states [ 268.181917] NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #282 [ 268.190585] numa_remove_cpu cpu 1 node 0: mask now 0,2-3,32-35 [ 268.194075] smpboot: CPU 1 is now offline [ 268.415320] x86: Booting SMP configuration: [ 268.420245] smpboot: Booting Node 0 Processor 1 APIC 0x2 # git clone https://github.com/cailca/linux-mm # cd linux-mm; make # ./random 4 (it just soft offline and online each CPU) The x86.config is also included there. This is only reproducible on x86 so far. > > --- > > tick-sched.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > index f0199a4..349a25a 100644 > --- a/kernel/time/tick-sched.c > +++ b/kernel/time/tick-sched.c > @@ -927,7 +927,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched > *ts) > > if (ratelimit < 10 && > (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { > - pr_warn("NOHZ: local_softirq_pending %02x\n", > + pr_warn("NOHZ tick-stop error: Non-RCU local softirq > work is pending, handler #%02x\n", > (unsigned int) local_softirq_pending()); > ratelimit++; > }
