On Fri, Jan 20, 2023 at 7:53 AM Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> wrote: > > On Fri, Jan 20, 2023 at 4:45 AM Joel Fernandes (Google) > <joel@xxxxxxxxxxxxxxxxx> wrote: > > > > For CONFIG_NO_HZ_FULL systems, the tick_do_timer_cpu cannot be offlined. > > However, cpu_is_hotpluggable() still returns true for those CPUs. This causes > > torture tests that do offlining to end up trying to offline this CPU causing > > test failures. Such failure happens on all architectures. > > > > Fix it by asking the opinion of the nohz subsystem on whether the CPU can > > be hotplugged. > > > > [ Apply Frederic Weisbecker feedback on refactoring tick_nohz_cpu_down(). ] > Thanks for your fantastic work > I applied this fix to linux-5.15.y, and perform new round of rcu > torture test on PPC VM of Open Source Lab of Oregon State University. > Could you please wait for the test to finish? > > The test results of linux-5.15.y before your patch can be viewed at [1] > The patched source code of linux-5.15.y can be viewed at [2] > The ongoing test of patched linux-5.15.y can be viewed at [3] > > [1] http://140.211.169.189/linux-stable-rc/tools/testing/selftests/rcutorture/res/2023.01.18-13.22.39-torture/ > [2] http://140.211.169.189/linux-stable-rc/ > [3] http://140.211.169.189/linux-stable-rc/tools/testing/selftests/rcutorture/res/2023.01.19-23.40.55-torture/ The rcutorture test on [3] has finished, by comparing the logs of [1] and [3], we can see Joel's patch fix the HOTPLUG problem without bring any new issues. Tested-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> Thanks Zhouyi > > Hope to continue to benefit the community. > > Thank you all > Zhouyi > > > > Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> > > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > > Cc: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx> > > Cc: Will Deacon <will@xxxxxxxxxx> > > Cc: Marc Zyngier <maz@xxxxxxxxxx> > > Cc: rcu <rcu@xxxxxxxxxxxxxxx> > > Fixes: 2987557f52b9 ("driver-core/cpu: Expose hotpluggability to the rest of the kernel") > > Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> > > --- > > drivers/base/cpu.c | 3 ++- > > include/linux/tick.h | 2 ++ > > kernel/time/tick-sched.c | 12 +++++++++++- > > 3 files changed, 15 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c > > index 55405ebf23ab..450dca235a2f 100644 > > --- a/drivers/base/cpu.c > > +++ b/drivers/base/cpu.c > > @@ -487,7 +487,8 @@ static const struct attribute_group *cpu_root_attr_groups[] = { > > bool cpu_is_hotpluggable(unsigned int cpu) > > { > > struct device *dev = get_cpu_device(cpu); > > - return dev && container_of(dev, struct cpu, dev)->hotpluggable; > > + return dev && container_of(dev, struct cpu, dev)->hotpluggable > > + && tick_nohz_cpu_hotpluggable(cpu); > > } > > EXPORT_SYMBOL_GPL(cpu_is_hotpluggable); > > > > diff --git a/include/linux/tick.h b/include/linux/tick.h > > index bfd571f18cfd..9459fef5b857 100644 > > --- a/include/linux/tick.h > > +++ b/include/linux/tick.h > > @@ -216,6 +216,7 @@ extern void tick_nohz_dep_set_signal(struct task_struct *tsk, > > enum tick_dep_bits bit); > > extern void tick_nohz_dep_clear_signal(struct signal_struct *signal, > > enum tick_dep_bits bit); > > +extern bool tick_nohz_cpu_hotpluggable(unsigned int cpu); > > > > /* > > * The below are tick_nohz_[set,clear]_dep() wrappers that optimize off-cases > > @@ -280,6 +281,7 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { } > > > > static inline void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) { } > > static inline void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { } > > +static inline bool tick_nohz_cpu_hotpluggable(unsigned int cpu) { return true; } > > > > static inline void tick_dep_set(enum tick_dep_bits bit) { } > > static inline void tick_dep_clear(enum tick_dep_bits bit) { } > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > > index 9c6f661fb436..383a060f30c5 100644 > > --- a/kernel/time/tick-sched.c > > +++ b/kernel/time/tick-sched.c > > @@ -510,7 +510,7 @@ void __init tick_nohz_full_setup(cpumask_var_t cpumask) > > tick_nohz_full_running = true; > > } > > > > -static int tick_nohz_cpu_down(unsigned int cpu) > > +static int tick_nohz_cpu_hotplug_ret(unsigned int cpu) > > { > > /* > > * The tick_do_timer_cpu CPU handles housekeeping duty (unbound > > @@ -522,6 +522,16 @@ static int tick_nohz_cpu_down(unsigned int cpu) > > return 0; > > } > > > > +static int tick_nohz_cpu_down(unsigned int cpu) > > +{ > > + return tick_nohz_cpu_hotplug_ret(cpu); > > +} > > + > > +bool tick_nohz_cpu_hotpluggable(unsigned int cpu) > > +{ > > + return tick_nohz_cpu_hotplug_ret(cpu) == 0; > > +} > > + > > void __init tick_nohz_init(void) > > { > > int cpu, ret; > > -- > > 2.39.0.246.g2a6d74b583-goog > >
