Commit de8cd0a5 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Update tree_exp.h function-header comments 



The function-header comments in kernel/rcu/tree_exp.h have gotten a bit
out of date, so this commit updates a number of them.

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent 6c7d7dbf

kernel/rcu/tree_exp.h

+13 −12
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ static void rcu_exp_gp_seq_start(void) 
}



/*

 * Return then value that expedited-grace-period counter will have

 * Return the value that the expedited-grace-period counter will have

 * at the end of the current grace period.

 */

static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void)
@@ -39,7 +39,9 @@ static void rcu_exp_gp_seq_end(void) 
}



/*

 * Take a snapshot of the expedited-grace-period counter.

 * Take a snapshot of the expedited-grace-period counter, which is the

 * earliest value that will indicate that a full grace period has

 * elapsed since the current time.

 */

static unsigned long rcu_exp_gp_seq_snap(void)

{
@@ -143,22 +145,18 @@ static void __maybe_unused sync_exp_reset_tree(void) 
 * Return non-zero if there is no RCU expedited grace period in progress

 * for the specified rcu_node structure, in other words, if all CPUs and

 * tasks covered by the specified rcu_node structure have done their bit

 * for the current expedited grace period.  Works only for preemptible

 * RCU -- other RCU implementation use other means.

 *

 * Caller must hold the specificed rcu_node structure's ->lock

 * for the current expedited grace period.

 */

static bool sync_rcu_exp_done(struct rcu_node *rnp)

{

	raw_lockdep_assert_held_rcu_node(rnp);



	return rnp->exp_tasks == NULL &&

	       READ_ONCE(rnp->expmask) == 0;

}



/*

 * Like sync_rcu_exp_done(), but this function assumes the caller doesn't

 * hold the rcu_node's ->lock, and will acquire and release the lock itself

 * Like sync_rcu_exp_done(), but where the caller does not hold the

 * rcu_node's ->lock.

 */

static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp)

{
@@ -180,8 +178,6 @@ static bool sync_rcu_exp_done_unlocked(struct rcu_node *rnp) 
 * which the task was queued or to one of that rcu_node structure's ancestors,

 * recursively up the tree.  (Calm down, calm down, we do the recursion

 * iteratively!)

 *

 * Caller must hold the specified rcu_node structure's ->lock.

 */

static void __rcu_report_exp_rnp(struct rcu_node *rnp,

				 bool wake, unsigned long flags)
@@ -189,6 +185,7 @@ static void __rcu_report_exp_rnp(struct rcu_node *rnp, 
{

	unsigned long mask;



	raw_lockdep_assert_held_rcu_node(rnp);

	for (;;) {

		if (!sync_rcu_exp_done(rnp)) {

			if (!rnp->expmask)
@@ -452,6 +449,10 @@ static void sync_rcu_exp_select_cpus(void) 
			flush_work(&rnp->rew.rew_work);

}



/*

 * Wait for the expedited grace period to elapse, issuing any needed

 * RCU CPU stall warnings along the way.

 */

static void synchronize_sched_expedited_wait(void)

{

	int cpu;
@@ -781,7 +782,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) 
 * implementations, it is still unfriendly to real-time workloads, so is

 * thus not recommended for any sort of common-case code.  In fact, if

 * you are using synchronize_rcu_expedited() in a loop, please restructure

 * your code to batch your updates, and then Use a single synchronize_rcu()

 * your code to batch your updates, and then use a single synchronize_rcu()

 * instead.

 *

 * This has the same semantics as (but is more brutal than) synchronize_rcu().