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rcu-tasks: Restore use of timers for non-RT kernels

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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 <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-03-18 08:08:14 -07:00
parent 777570d9ef
commit bddf7122f7
1 changed files with 7 additions and 3 deletions
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10
kernel/rcu/tasks.h
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@ -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++;