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author | Scott Wood <swood@redhat.com> | 2020-12-15 15:16:46 +0100 |
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committer | Paul E. McKenney <paulmck@kernel.org> | 2021-01-04 13:43:51 -0800 |
commit | 8b9a0ecc7ef5e1ed3afbc926de17399a37128c82 (patch) | |
tree | 66d0c14ef24894b8ac54e1c1eebe4f27777fa28b /kernel | |
parent | 2341bc4a0311e4319ced6c2828bb19309dee74fd (diff) | |
download | linux-stable-8b9a0ecc7ef5e1ed3afbc926de17399a37128c82.tar.gz linux-stable-8b9a0ecc7ef5e1ed3afbc926de17399a37128c82.tar.bz2 linux-stable-8b9a0ecc7ef5e1ed3afbc926de17399a37128c82.zip |
rcu: Unconditionally use rcuc threads on PREEMPT_RT
PREEMPT_RT systems have long used the rcutree.use_softirq kernel
boot parameter to avoid use of RCU_SOFTIRQ handlers, which can disrupt
real-time applications by invoking callbacks during return from interrupts
that arrived while executing time-critical code. This kernel boot
parameter instead runs RCU core processing in an 'rcuc' kthread, thus
allowing the scheduler to do its job of avoiding disrupting time-critical
code.
This commit therefore disables the rcutree.use_softirq kernel boot
parameter on PREEMPT_RT systems, thus forcing such systems to do RCU
core processing in 'rcuc' kthreads. This approach has long been in
use by users of the -rt patchset, and there have been no complaints.
There is therefore no way for the system administrator to override this
choice, at least without modifying and rebuilding the kernel.
Signed-off-by: Scott Wood <swood@redhat.com>
[bigeasy: Reword commit message]
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')
-rw-r--r-- | kernel/rcu/tree.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 40e5e3dd253e..d60903581300 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -100,8 +100,10 @@ static struct rcu_state rcu_state = { static bool dump_tree; module_param(dump_tree, bool, 0444); /* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */ -static bool use_softirq = true; +static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT); +#ifndef CONFIG_PREEMPT_RT module_param(use_softirq, bool, 0444); +#endif /* Control rcu_node-tree auto-balancing at boot time. */ static bool rcu_fanout_exact; module_param(rcu_fanout_exact, bool, 0444); |