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authorJulia Cartwright <julia@ni.com>2020-12-15 15:16:47 +0100
committerPaul E. McKenney <paulmck@kernel.org>2021-01-04 13:43:51 -0800
commit36221e109eb20ac111bc3bf3e8d5639aa457c7e0 (patch)
treeb636272ab3062d4f1db2e2ab8b11d4ddcef7a8b2 /kernel/locking
parent8b9a0ecc7ef5e1ed3afbc926de17399a37128c82 (diff)
rcu: Enable rcu_normal_after_boot unconditionally for RT
Expedited RCU grace periods send IPIs to all non-idle CPUs, and thus can disrupt time-critical code in real-time applications. However, there is a portion of boot-time processing (presumably before any real-time applications have started) where expedited RCU grace periods are the only option. And so it is that experience with the -rt patchset indicates that PREEMPT_RT systems should always set the rcupdate.rcu_normal_after_boot kernel boot parameter. This commit therefore makes the post-boot application environment safe for real-time applications by making PREEMPT_RT systems disable the rcupdate.rcu_normal_after_boot kernel boot parameter and acting as if this parameter had been set. This means that post-boot calls to synchronize_rcu_expedited() will be treated as if they were instead calls to synchronize_rcu(), thus preventing the IPIs, and thus avoiding disrupting real-time applications. Suggested-by: Luiz Capitulino <lcapitulino@redhat.com> Acked-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Julia Cartwright <julia@ni.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> [ paulmck: Update kernel-parameters.txt accordingly. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/locking')
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