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rcu: Add CONFIG_RCU_LAZY delays to call_rcu() kernel-doc header

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This commit adds a description of the energy-efficiency delays that
call_rcu() can impose, along with a pointer to call_rcu_hurry() for
latency-sensitive kernel code.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This commit is contained in:
Paul E. McKenney 2025-01-08 19:42:42 -08:00 committed by Boqun Feng
parent 366ba3f7f9
commit 053ca72554
1 changed files with 7 additions and 0 deletions
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7
kernel/rcu/tree.c
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@ -3172,6 +3172,13 @@ EXPORT_SYMBOL_GPL(call_rcu_hurry);
*
* Implementation of these memory-ordering guarantees is described here:
* Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst.
*
* Specific to call_rcu() (as opposed to the other call_rcu*() functions),
* in kernels built with CONFIG_RCU_LAZY=y, call_rcu() might delay for many
* seconds before starting the grace period needed by the corresponding
* callback. This delay can significantly improve energy-efficiency
* on low-utilization battery-powered devices. To avoid this delay,
* in latency-sensitive kernel code, use call_rcu_hurry().
*/
void call_rcu(struct rcu_head *head, rcu_callback_t func)
{