From 81ad58be2f83f9bd675f67ca5b8f420358ddf13c Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Tue, 15 Dec 2020 15:16:49 +0100 Subject: doc: Use CONFIG_PREEMPTION CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same functionality which today depends on CONFIG_PREEMPT. Update the documents and mention CONFIG_PREEMPTION. Spell out CONFIG_PREEMPT_RT (instead PREEMPT_RT) since it is an option now. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney --- Documentation/RCU/rcubarrier.rst | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'Documentation/RCU/rcubarrier.rst') diff --git a/Documentation/RCU/rcubarrier.rst b/Documentation/RCU/rcubarrier.rst index f64f4413a47c..3b4a24877496 100644 --- a/Documentation/RCU/rcubarrier.rst +++ b/Documentation/RCU/rcubarrier.rst @@ -9,7 +9,7 @@ RCU (read-copy update) is a synchronization mechanism that can be thought of as a replacement for read-writer locking (among other things), but with very low-overhead readers that are immune to deadlock, priority inversion, and unbounded latency. RCU read-side critical sections are delimited -by rcu_read_lock() and rcu_read_unlock(), which, in non-CONFIG_PREEMPT +by rcu_read_lock() and rcu_read_unlock(), which, in non-CONFIG_PREEMPTION kernels, generate no code whatsoever. This means that RCU writers are unaware of the presence of concurrent @@ -329,10 +329,10 @@ Answer: This cannot happen. The reason is that on_each_cpu() has its last to smp_call_function() and further to smp_call_function_on_cpu(), causing this latter to spin until the cross-CPU invocation of rcu_barrier_func() has completed. This by itself would prevent - a grace period from completing on non-CONFIG_PREEMPT kernels, + a grace period from completing on non-CONFIG_PREEMPTION kernels, since each CPU must undergo a context switch (or other quiescent state) before the grace period can complete. However, this is - of no use in CONFIG_PREEMPT kernels. + of no use in CONFIG_PREEMPTION kernels. Therefore, on_each_cpu() disables preemption across its call to smp_call_function() and also across the local call to -- cgit v1.2.3