Commit 053ca725 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Boqun Feng
Browse files

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



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: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
parent 366ba3f7

kernel/rcu/tree.c

+7 −0
Original line number Diff line number Diff line
@@ -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)

{