From: "Paul E. McKenney" <paulmck@xxxxxxxxxx> This commit documents the fact that a given RCU callback function can repost itself. Reported-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx> --- kernel/rcu/tree.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 475f31deed14..2cd193ed854c 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3107,7 +3107,7 @@ module_param(enable_rcu_lazy, bool, 0444); * critical sections have completed. * * Use this API instead of call_rcu() if you don't want the callback to be - * invoked after very long periods of time, which can happen on systems without + * delayed for very long periods of time, which can happen on systems without * memory pressure and on systems which are lightly loaded or mostly idle. * This function will cause callbacks to be invoked sooner than later at the * expense of extra power. Other than that, this function is identical to, and @@ -3138,6 +3138,12 @@ EXPORT_SYMBOL_GPL(call_rcu_hurry); * might well execute concurrently with RCU read-side critical sections * that started after call_rcu() was invoked. * + * It is perfectly legal to repost an RCU callback, potentially with + * a different callback function, from within its callback function. + * The specified function will be invoked after another full grace period + * has elapsed. This use case is similar in form to the common practice + * of reposting a timer from within its own handler. + * * RCU read-side critical sections are delimited by rcu_read_lock() * and rcu_read_unlock(), and may be nested. In addition, but only in * v5.0 and later, regions of code across which interrupts, preemption, -- 2.39.5 (Apple Git-154)
