rcu: Finer-grained grace-period-end checks in rcu_dump_cpu_stacks()

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This commit pushes the grace-period-end checks further down into
rcu_dump_cpu_stacks(), and also uses lockless checks coupled with
finer-grained locking.

The result is that the current leaf rcu_node structure's ->lock is
acquired only if a stack backtrace might be needed from the current CPU,
and is held across only that CPU's backtrace.  As a result, if there are
no stalled CPUs associated with a given rcu_node structure, then its
->lock will not be acquired at all.  On large systems, it is usually
(though not always) the case that a small number of CPUs are stalling
the current grace period, which means that the ->lock need be acquired
only for a small fraction of the rcu_node structures.

[ paulmck: Apply Dan Carpenter feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

...

This commit is contained in:

Paul E. McKenney 2024-10-28 17:22:51 -07:00 • committed by Frederic Weisbecker

parent cbe644aa6f

commit 9650edd9bf

1 changed files with 11 additions and 7 deletions

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kernel/rcu/tree_stall.h

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