On Fri, 09 Nov 2018 18:41:03 +0000, Qian Cai <c...@gmx.us> wrote: > > > > > On Nov 9, 2018, at 12:41 PM, Marc Zyngier <marc.zyng...@arm.com> wrote: > > > > On 09/11/18 17:28, Sudeep Holla wrote: > >> On Fri, Nov 9, 2018 at 4:10 PM Marc Zyngier <marc.zyng...@arm.com> wrote: > >>> > >> [...] > >> > >>> > >>> See bb42ca474010 and d003d029cea8 for details. > >>> > >>> Now, activating this workaround leads to lockdep being really angry, > >>> most likely because the cpus_read_lock is not taken, which is a change > >>> in behaviour... > >>> > >>> I'm trying to dig into this now. > >>> > >> > >> Yes we found similar issue in kernel/sched/core.c sched_init_smp > >> There's a fix with detailed description in -next > >> (Commit 40fa3780bac2 ("sched/core: Take the hotplug lock in > >> sched_init_smp()") > >> > >> The behaviour changed since commit cb538267ea1e ("jump_label/lockdep: > >> Assert we hold the hotplug lock for _cpuslocked() operations") > > > > I indeed came to the same conclusion, but the fix is slightly less than > > obvious. I have the following arm64-specific crap, but it is pretty > > terrible: > > > > diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c > > index f258636273c9..9e96e9eaca9b 100644 > > --- a/arch/arm64/kernel/time.c > > +++ b/arch/arm64/kernel/time.c > > @@ -36,6 +36,7 @@ > > #include <linux/clocksource.h> > > #include <linux/clk-provider.h> > > #include <linux/acpi.h> > > +#include <linux/cpu.h> > > > > #include <clocksource/arm_arch_timer.h> > > > > @@ -69,7 +70,9 @@ void __init time_init(void) > > u32 arch_timer_rate; > > > > of_clk_init(NULL); > > + cpus_read_lock(); > > timer_probe(); > > + cpus_read_unlock(); > > > > tick_setup_hrtimer_broadcast(); > > > > Qian, can you please let me know if this helps? If it does, we'll have > > to think of something a bit better… > After applied the above patch, the original warning is gone but there > Is now a new warning.
[...] Which was ful;ly expected, given that I've taken the cpu lock at some semi-random location. I'll try to talk to PeterZ this week to try and solve this. Thanks, M. -- Jazz is not dead, it just smell funny.