The RCU Tasks Rude grace period is implemented by invoking the schedule_on_each_cpu() with an empty work function, which forces a context switch on every online CPU and guarantees that all rude-tasks read-side critical sections have completed. However, schedule_on_each_cpu() can fail (via alloc_percpu() returning -ENOMEM) and returns immediately, in which case those context switches never happen, too-short grace period happen.
This commit therefore wraps the schedule_on_each_cpu() call in WARN_ONCE() so that this failure is reported as a "Too-short grace period" warning. Signed-off-by: Zqiang <[email protected]> --- kernel/rcu/tasks.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index fcac7361ec51..91c25717402e 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -1361,7 +1361,8 @@ static void rcu_tasks_be_rude(struct work_struct *work) static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp) { rtp->n_ipis += cpumask_weight(cpu_online_mask); - schedule_on_each_cpu(rcu_tasks_be_rude); + WARN_ONCE(schedule_on_each_cpu(rcu_tasks_be_rude), + "%s: Too-short grace period, OOM is now expected behavior!!!\n", rtp->name); } static void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func); -- 2.17.1
