iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

rcu: Make rcu_normal_after_boot writable again

Browse Source 
Certain configurations (e.g., systems that make heavy use of netns)
need to use synchronize_rcu_expedited() to service RCU grace periods
even after boot.

Even though synchronize_rcu_expedited() has been traditionally
considered harmful for RT for the heavy use of IPIs, it is perfectly
usable under certain conditions (e.g. nohz_full).

Make rcupdate.rcu_normal_after_boot= again writeable on RT (if NO_HZ_
FULL is defined), but keep its default value to 1 (enabled) to avoid
regressions. Users who need synchronize_rcu_expedited() will boot with
rcupdate.rcu_normal_after_ boot=0 in the kernel cmdline.

Reflect the change in synchronize_rcu_expedited_wait() by removing the
WARN related to CONFIG_PREEMPT_RT.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Juri Lelli 2021-08-10 10:48:15 +02:00 committed by Paul E. McKenney
parent 4aa846f97c
commit ebb6d30d9e
2 changed files with 1 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
kernel/rcu/tree_exp.h
View File

@ -512,7 +512,6 @@ static void synchronize_rcu_expedited_wait(void)
j = READ_ONCE(jiffies_till_first_fqs);
if (synchronize_rcu_expedited_wait_once(j + HZ))
return;
WARN_ON_ONCE(IS_ENABLED(CONFIG_PREEMPT_RT));
}
for (;;) {

2
kernel/rcu/update.c
View File

@ -57,7 +57,7 @@
module_param(rcu_expedited, int, 0);
module_param(rcu_normal, int, 0);
static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT);
#ifndef CONFIG_PREEMPT_RT
#if !defined(CONFIG_PREEMPT_RT) || defined(CONFIG_NO_HZ_FULL)
module_param(rcu_normal_after_boot, int, 0);
#endif
#endif /* #ifndef CONFIG_TINY_RCU */