From: Frederic Weisbecker frederic@kernel.org
cpusets is going to use the NOCB (de-)offloading interface while holding hotplug lock. Therefore pull out the responsibility of protecting against concurrent CPU-hotplug changes to the callers of rcu_nocb_cpumask_update().
Signed-off-by: Frederic Weisbecker frederic@kernel.org Cc: Zefan Li lizefan.x@bytedance.com Cc: Tejun Heo tj@kernel.org Cc: Johannes Weiner hannes@cmpxchg.org Cc: Paul E. McKenney paulmck@kernel.org Cc: Phil Auld pauld@redhat.com Cc: Nicolas Saenz Julienne nsaenz@kernel.org Cc: Marcelo Tosatti mtosatti@redhat.com Cc: Paul Gortmaker paul.gortmaker@windriver.com Cc: Waiman Long longman@redhat.com Cc: Daniel Bristot de Oliveira bristot@kernel.org Cc: Peter Zijlstra peterz@infradead.org --- kernel/rcu/rcutorture.c | 2 ++ kernel/rcu/tree_nocb.h | 4 ++-- 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 228a5488eb5e..e935152346ff 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -2139,6 +2139,7 @@ static int rcu_nocb_toggle(void *arg) do { r = torture_random(&rand); cpu = (r >> 1) % (maxcpu + 1); + cpus_read_lock(); if (r & 0x1) { rcu_nocb_cpumask_update(cpumask_of(cpu), true); atomic_long_inc(&n_nocb_offload); @@ -2146,6 +2147,7 @@ static int rcu_nocb_toggle(void *arg) rcu_nocb_cpumask_update(cpumask_of(cpu), false); atomic_long_inc(&n_nocb_deoffload); } + cpus_read_unlock(); toggle_delay = torture_random(&rand) % toggle_fuzz + toggle_interval; set_current_state(TASK_INTERRUPTIBLE); schedule_hrtimeout(&toggle_delay, HRTIMER_MODE_REL); diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 60b0a15ed6e2..bbcf6f4152a3 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -1301,12 +1301,13 @@ int rcu_nocb_cpumask_update(const struct cpumask *cpumask, bool offload) int err_cpu; cpumask_var_t saved_nocb_mask;
+ lockdep_assert_cpus_held(); + if (!alloc_cpumask_var(&saved_nocb_mask, GFP_KERNEL)) return -ENOMEM;
cpumask_copy(saved_nocb_mask, rcu_nocb_mask);
- cpus_read_lock(); mutex_lock(&rcu_state.barrier_mutex); for_each_cpu(cpu, cpumask) { if (offload) { @@ -1340,7 +1341,6 @@ int rcu_nocb_cpumask_update(const struct cpumask *cpumask, bool offload) }
mutex_unlock(&rcu_state.barrier_mutex); - cpus_read_unlock();
free_cpumask_var(saved_nocb_mask);