rcu: Make rcu_normal_after_boot writable again

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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>

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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

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1

kernel/rcu/tree_exp.h

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2

kernel/rcu/update.c

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