From: Joel Fernandes (Google) joel@joelfernandes.org
commit 58d7668242647e661a20efe065519abd6454287e upstream.
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 the repeated error messages thrown by this (even if the hotplug errors are harmless) 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(). ]
For drivers/base/ portion: Acked-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Acked-by: Frederic Weisbecker frederic@kernel.org Cc: Frederic Weisbecker frederic@kernel.org Cc: "Paul E. McKenney" paulmck@kernel.org Cc: Zhouyi Zhou zhouzhouyi@gmail.com Cc: Will Deacon will@kernel.org Cc: Marc Zyngier maz@kernel.org Cc: rcu rcu@vger.kernel.org Cc: stable@vger.kernel.org Fixes: 2987557f52b9 ("driver-core/cpu: Expose hotpluggability to the rest of the kernel") Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Joel Fernandes (Google) joel@joelfernandes.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/base/cpu.c | 3 ++- include/linux/tick.h | 2 ++ kernel/time/tick-sched.c | 11 ++++++++--- 3 files changed, 12 insertions(+), 4 deletions(-)
--- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -487,7 +487,8 @@ static const struct attribute_group *cpu 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);
--- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -216,6 +216,7 @@ extern void tick_nohz_dep_set_signal(str 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_cp
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) { } --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -510,7 +510,7 @@ void __init tick_nohz_full_setup(cpumask tick_nohz_full_running = true; }
-static int tick_nohz_cpu_down(unsigned int cpu) +bool tick_nohz_cpu_hotpluggable(unsigned int cpu) { /* * The tick_do_timer_cpu CPU handles housekeeping duty (unbound @@ -518,8 +518,13 @@ static int tick_nohz_cpu_down(unsigned i * CPUs. It must remain online when nohz full is enabled. */ if (tick_nohz_full_running && tick_do_timer_cpu == cpu) - return -EBUSY; - return 0; + return false; + return true; +} + +static int tick_nohz_cpu_down(unsigned int cpu) +{ + return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY; }
void __init tick_nohz_init(void)