From bddf7122f7e321d5a677a695e8597064d987482c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 18 Mar 2022 08:08:14 -0700 Subject: [PATCH] rcu-tasks: Restore use of timers for non-RT kernels The use of hrtimers for RCU-tasks grace-period delays works well in general, but can result in excessive grace-period delays for some corner-case workloads. This commit therefore reverts to the use of timers for non-RT kernels to mitigate those grace-period delays. Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 71fe340ab82a..405614039515 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -654,9 +654,13 @@ static void rcu_tasks_wait_gp(struct rcu_tasks *rtp) // Slowly back off waiting for holdouts set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS); - exp = jiffies_to_nsecs(fract); - __set_current_state(TASK_IDLE); - schedule_hrtimeout_range(&exp, jiffies_to_nsecs(HZ / 2), HRTIMER_MODE_REL_HARD); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { + schedule_timeout_idle(fract); + } else { + exp = jiffies_to_nsecs(fract); + __set_current_state(TASK_IDLE); + schedule_hrtimeout_range(&exp, jiffies_to_nsecs(HZ / 2), HRTIMER_MODE_REL_HARD); + } if (fract < HZ) fract++;