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| author |   Juri Lelli <juri.lelli@redhat.com> | 2021-08-10 10:48:15 +0200 |
|---|---|---|
| committer |   Paul E. McKenney <paulmck@kernel.org> | 2021-09-13 16:32:46 -0700 |
| commit | ebb6d30d9ed1fe7137486e1be2ae9d621e918c4a (patch) | |
| tree | 8410a44321e9f576f68d2363aab8040ce53223a6 /kernel/rcu | |
| parent | rcu: Make rcutree_dying_cpu() use its "cpu" parameter (diff) | |
| download | linux-dev-ebb6d30d9ed1fe7137486e1be2ae9d621e918c4a.tar.xz linux-dev-ebb6d30d9ed1fe7137486e1be2ae9d621e918c4a.zip | |
rcu: Make rcu_normal_after_boot writable again
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>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tree_exp.h | 1 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 2 |
2 files changed, 1 insertions, 2 deletions
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 2796084ef85a..d9e4f8eb9ae2 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -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 (;;) { diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index c21b38cc25e9..bd551134e2f4 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -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 */ |