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rcu: Document self-propagating callbacks

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This commit documents the fact that a given RCU callback function can
repost itself.

Reported-by: Jens Axboe <axboe@kernel.dk>
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 16:53:02 -08:00 committed by Boqun Feng
parent df0cee4311
commit 21ef249862
1 changed files with 7 additions and 1 deletions
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8
kernel/rcu/tree.c
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@ -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,