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Commit 77d8485a authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: improve kerneldoc for rcu_read_lock(), call_rcu(), and synchronize_rcu() 



Make it explicit that new RCU read-side critical sections that start
after call_rcu() and synchronize_rcu() start might still be running
after the end of the relevant grace period.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent 742734ee

include/linux/rcupdate.h

+9 −7
Original line number Diff line number Diff line
@@ -450,7 +450,7 @@ extern int rcu_my_thread_group_empty(void); 
 * until after the all the other CPUs exit their critical sections.

 *

 * Note, however, that RCU callbacks are permitted to run concurrently

 * with RCU read-side critical sections.  One way that this can happen

 * with new RCU read-side critical sections.  One way that this can happen

 * is via the following sequence of events: (1) CPU 0 enters an RCU

 * read-side critical section, (2) CPU 1 invokes call_rcu() to register

 * an RCU callback, (3) CPU 0 exits the RCU read-side critical section,
@@ -608,11 +608,13 @@ extern void wakeme_after_rcu(struct rcu_head *head); 
/**

 * call_rcu() - Queue an RCU callback for invocation after a grace period.

 * @head: structure to be used for queueing the RCU updates.

 * @func: actual update function to be invoked after the grace period

 * @func: actual callback function to be invoked after the grace period

 *

 * The update function will be invoked some time after a full grace

 * period elapses, in other words after all currently executing RCU

 * read-side critical sections have completed.  RCU read-side critical

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all pre-existing RCU read-side

 * critical sections have completed.  However, the callback function

 * might well execute concurrently with RCU read-side critical sections

 * that started after call_rcu() was invoked.  RCU read-side critical

 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),

 * and may be nested.

 */
@@ -622,9 +624,9 @@ extern void call_rcu(struct rcu_head *head, 
/**

 * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.

 * @head: structure to be used for queueing the RCU updates.

 * @func: actual update function to be invoked after the grace period

 * @func: actual callback function to be invoked after the grace period

 *

 * The update function will be invoked some time after a full grace

 * The callback function will be invoked some time after a full grace

 * period elapses, in other words after all currently executing RCU

 * read-side critical sections have completed. call_rcu_bh() assumes

 * that the read-side critical sections end on completion of a softirq

kernel/rcutree_plugin.h

+5 −3
Original line number Diff line number Diff line
@@ -546,9 +546,11 @@ EXPORT_SYMBOL_GPL(call_rcu); 
 *

 * Control will return to the caller some time after a full grace

 * period has elapsed, in other words after all currently executing RCU

 * read-side critical sections have completed.  RCU read-side critical

 * sections are delimited by rcu_read_lock() and rcu_read_unlock(),

 * and may be nested.

 * read-side critical sections have completed.  Note, however, that

 * upon return from synchronize_rcu(), the caller might well be executing

 * concurrently with new RCU read-side critical sections that began while

 * synchronize_rcu() was waiting.  RCU read-side critical sections are

 * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested.

 */

void synchronize_rcu(void)

{