rcu/nocb: Simplify (de-)offloading state machine

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Now that the (de-)offloading process can only apply to offline CPUs,
there is no more concurrency between rcu_core and nocb kthreads. Also
the mutation now happens on empty queues.

Therefore the state machine can be reduced to a single bit called
SEGCBLIST_OFFLOADED. Simplify the transition as follows:

* Upon offloading: queue the rdp to be added to the rcuog list and
  wait for the rcuog kthread to set the SEGCBLIST_OFFLOADED bit. Unpark
  rcuo kthread.

* Upon de-offloading: Park rcuo kthread. Queue the rdp to be removed
  from the rcuog list and wait for the rcuog kthread to clear the
  SEGCBLIST_OFFLOADED bit.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>

...

This commit is contained in:

Frederic Weisbecker 2024-07-04 00:56:40 +02:00 • committed by Neeraj Upadhyay

parent 91e43b9044

commit 1fcb932c8b

4 changed files with 68 additions and 87 deletions

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4

include/linux/rcu_segcblist.h

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11

kernel/rcu/rcu_segcblist.c

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2

kernel/rcu/rcu_segcblist.h

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138

kernel/rcu/tree_nocb.h

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