rcu: Separately compile large rcu_segcblist functions

This commit creates a new kernel/rcu/rcu_segcblist.c file that
contains non-trivial segcblist functions.  Trivial functions
remain as static inline functions in kernel/rcu/rcu_segcblist.h

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 35 insertions, 498 deletions

diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index d98d2f9b8d59..86bc1101b806 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -1,5 +1,5 @@
 /*
- * RCU segmented callback lists
+ * RCU segmented callback lists, internal-to-rcu header file
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -22,15 +22,6 @@
 
 #include <linux/rcu_segcblist.h>
 
-/* Initialize simple callback list. */
-static inline void rcu_cblist_init(struct rcu_cblist *rclp)
-{
-	rclp->head = NULL;
-	rclp->tail = &rclp->head;
-	rclp->len = 0;
-	rclp->len_lazy = 0;
-}
-
 /* Is simple callback list empty? */
 static inline bool rcu_cblist_empty(struct rcu_cblist *rclp)
 {
@@ -50,45 +41,6 @@ static inline long rcu_cblist_n_lazy_cbs(struct rcu_cblist *rclp)
 }
 
 /*
- * Debug function to actually count the number of callbacks.
- * If the number exceeds the limit specified, return -1.
- */
-static inline long rcu_cblist_count_cbs(struct rcu_cblist *rclp, long lim)
-{
-	int cnt = 0;
-	struct rcu_head **rhpp = &rclp->head;
-
-	for (;;) {
-		if (!*rhpp)
-			return cnt;
-		if (++cnt > lim)
-			return -1;
-		rhpp = &(*rhpp)->next;
-	}
-}
-
-/*
- * Dequeue the oldest rcu_head structure from the specified callback
- * list.  This function assumes that the callback is non-lazy, but
- * the caller can later invoke rcu_cblist_dequeued_lazy() if it
- * finds otherwise (and if it cares about laziness).  This allows
- * different users to have different ways of determining laziness.
- */
-static inline struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp)
-{
-	struct rcu_head *rhp;
-
-	rhp = rclp->head;
-	if (!rhp)
-		return NULL;
-	rclp->len--;
-	rclp->head = rhp->next;
-	if (!rclp->head)
-		rclp->tail = &rclp->head;
-	return rhp;
-}
-
-/*
  * Account for the fact that a previously dequeued callback turned out
  * to be marked as lazy.
  */
@@ -118,21 +70,9 @@ static inline struct rcu_head **rcu_cblist_tail(struct rcu_cblist *rclp)
 	return rclp->tail;
 }
 
-/*
- * Initialize an rcu_segcblist structure.
- */
-static inline void rcu_segcblist_init(struct rcu_segcblist *rsclp)
-{
-	int i;
-
-	BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq));
-	BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq));
-	rsclp->head = NULL;
-	for (i = 0; i < RCU_CBLIST_NSEGS; i++)
-		rsclp->tails[i] = &rsclp->head;
-	rsclp->len = 0;
-	rsclp->len_lazy = 0;
-}
+void rcu_cblist_init(struct rcu_cblist *rclp);
+long rcu_cblist_count_cbs(struct rcu_cblist *rclp, long lim);
+struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp);
 
 /*
  * Is the specified rcu_segcblist structure empty?
@@ -180,29 +120,6 @@ static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
 }
 
 /*
- * Disable the specified rcu_segcblist structure, so that callbacks can
- * no longer be posted to it.  This structure must be empty.
- */
-static inline void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
-{
-	WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));
-	WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));
-	WARN_ON_ONCE(rcu_segcblist_n_lazy_cbs(rsclp));
-	rsclp->tails[RCU_NEXT_TAIL] = NULL;
-}
-
-/*
- * Is the specified segment of the specified rcu_segcblist structure
- * empty of callbacks?
- */
-static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
-{
-	if (seg == RCU_DONE_TAIL)
-		return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
-	return rsclp->tails[seg - 1] == rsclp->tails[seg];
-}
-
-/*
  * Are all segments following the specified segment of the specified
  * rcu_segcblist structure empty of callbacks?  (The specified
  * segment might well contain callbacks.)
@@ -213,417 +130,6 @@ static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
 }
 
 /*
- * Does the specified rcu_segcblist structure contain callbacks that
- * are ready to be invoked?
- */
-static inline bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp)
-{
-	return rcu_segcblist_is_enabled(rsclp) &&
-	       &rsclp->head != rsclp->tails[RCU_DONE_TAIL];
-}
-
-/*
- * Does the specified rcu_segcblist structure contain callbacks that
- * are still pending, that is, not yet ready to be invoked?
- */
-static inline bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp)
-{
-	return rcu_segcblist_is_enabled(rsclp) &&
-	       !rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL);
-}
-
-/*
- * Dequeue and return the first ready-to-invoke callback.  If there
- * are no ready-to-invoke callbacks, return NULL.  Disables interrupts
- * to avoid interference.  Does not protect from interference from other
- * CPUs or tasks.
- */
-static inline struct rcu_head *
-rcu_segcblist_dequeue(struct rcu_segcblist *rsclp)
-{
-	unsigned long flags;
-	int i;
-	struct rcu_head *rhp;
-
-	local_irq_save(flags);
-	if (!rcu_segcblist_ready_cbs(rsclp)) {
-		local_irq_restore(flags);
-		return NULL;
-	}
-	rhp = rsclp->head;
-	BUG_ON(!rhp);
-	rsclp->head = rhp->next;
-	for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) {
-		if (rsclp->tails[i] != &rhp->next)
-			break;
-		rsclp->tails[i] = &rsclp->head;
-	}
-	smp_mb(); /* Dequeue before decrement for rcu_barrier(). */
-	WRITE_ONCE(rsclp->len, rsclp->len - 1);
-	local_irq_restore(flags);
-	return rhp;
-}
-
-/*
- * Account for the fact that a previously dequeued callback turned out
- * to be marked as lazy.
- */
-static inline void rcu_segcblist_dequeued_lazy(struct rcu_segcblist *rsclp)
-{
-	unsigned long flags;
-
-	local_irq_save(flags);
-	rsclp->len_lazy--;
-	local_irq_restore(flags);
-}
-
-/*
- * Return a pointer to the first callback in the specified rcu_segcblist
- * structure.  This is useful for diagnostics.
- */
-static inline struct rcu_head *
-rcu_segcblist_first_cb(struct rcu_segcblist *rsclp)
-{
-	if (rcu_segcblist_is_enabled(rsclp))
-		return rsclp->head;
-	return NULL;
-}
-
-/*
- * Return a pointer to the first pending callback in the specified
- * rcu_segcblist structure.  This is useful just after posting a given
- * callback -- if that callback is the first pending callback, then
- * you cannot rely on someone else having already started up the required
- * grace period.
- */
-static inline struct rcu_head *
-rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp)
-{
-	if (rcu_segcblist_is_enabled(rsclp))
-		return *rsclp->tails[RCU_DONE_TAIL];
-	return NULL;
-}
-
-/*
- * Does the specified rcu_segcblist structure contain callbacks that
- * have not yet been processed beyond having been posted, that is,
- * does it contain callbacks in its last segment?
- */
-static inline bool rcu_segcblist_new_cbs(struct rcu_segcblist *rsclp)
-{
-	return rcu_segcblist_is_enabled(rsclp) &&
-	       !rcu_segcblist_restempty(rsclp, RCU_NEXT_READY_TAIL);
-}
-
-/*
- * Enqueue the specified callback onto the specified rcu_segcblist
- * structure, updating accounting as needed.  Note that the ->len
- * field may be accessed locklessly, hence the WRITE_ONCE().
- * The ->len field is used by rcu_barrier() and friends to determine
- * if it must post a callback on this structure, and it is OK
- * for rcu_barrier() to sometimes post callbacks needlessly, but
- * absolutely not OK for it to ever miss posting a callback.
- */
-static inline void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
-					 struct rcu_head *rhp, bool lazy)
-{
-	WRITE_ONCE(rsclp->len, rsclp->len + 1); /* ->len sampled locklessly. */
-	if (lazy)
-		rsclp->len_lazy++;
-	smp_mb(); /* Ensure counts are updated before callback is enqueued. */
-	rhp->next = NULL;
-	*rsclp->tails[RCU_NEXT_TAIL] = rhp;
-	rsclp->tails[RCU_NEXT_TAIL] = &rhp->next;
-}
-
-/*
- * Entrain the specified callback onto the specified rcu_segcblist at
- * the end of the last non-empty segment.  If the entire rcu_segcblist
- * is empty, make no change, but return false.
- *
- * This is intended for use by rcu_barrier()-like primitives, -not-
- * for normal grace-period use.  IMPORTANT:  The callback you enqueue
- * will wait for all prior callbacks, NOT necessarily for a grace
- * period.  You have been warned.
- */
-static inline bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
-					 struct rcu_head *rhp, bool lazy)
-{
-	int i;
-
-	if (rcu_segcblist_n_cbs(rsclp) == 0)
-		return false;
-	WRITE_ONCE(rsclp->len, rsclp->len + 1);
-	if (lazy)
-		rsclp->len_lazy++;
-	smp_mb(); /* Ensure counts are updated before callback is entrained. */
-	rhp->next = NULL;
-	for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--)
-		if (rsclp->tails[i] != rsclp->tails[i - 1])
-			break;
-	*rsclp->tails[i] = rhp;
-	for (; i <= RCU_NEXT_TAIL; i++)
-		rsclp->tails[i] = &rhp->next;
-	return true;
-}
-
-/*
- * Extract only the counts from the specified rcu_segcblist structure,
- * and place them in the specified rcu_cblist structure.  This function
- * supports both callback orphaning and invocation, hence the separation
- * of counts and callbacks.  (Callbacks ready for invocation must be
- * orphaned and adopted separately from pending callbacks, but counts
- * apply to all callbacks.  Locking must be used to make sure that
- * both orphaned-callbacks lists are consistent.)
- */
-static inline void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
-					       struct rcu_cblist *rclp)
-{
-	rclp->len_lazy += rsclp->len_lazy;
-	rclp->len += rsclp->len;
-	rsclp->len_lazy = 0;
-	WRITE_ONCE(rsclp->len, 0); /* ->len sampled locklessly. */
-}
-
-/*
- * Extract only those callbacks ready to be invoked from the specified
- * rcu_segcblist structure and place them in the specified rcu_cblist
- * structure.
- */
-static inline void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
-						  struct rcu_cblist *rclp)
-{
-	int i;
-
-	if (!rcu_segcblist_ready_cbs(rsclp))
-		return; /* Nothing to do. */
-	*rclp->tail = rsclp->head;
-	rsclp->head = *rsclp->tails[RCU_DONE_TAIL];
-	*rsclp->tails[RCU_DONE_TAIL] = NULL;
-	rclp->tail = rsclp->tails[RCU_DONE_TAIL];
-	for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--)
-		if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL])
-			rsclp->tails[i] = &rsclp->head;
-}
-
-/*
- * Extract only those callbacks still pending (not yet ready to be
- * invoked) from the specified rcu_segcblist structure and place them in
- * the specified rcu_cblist structure.  Note that this loses information
- * about any callbacks that might have been partway done waiting for
- * their grace period.  Too bad!  They will have to start over.
- */
-static inline void
-rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
-			       struct rcu_cblist *rclp)
-{
-	int i;
-
-	if (!rcu_segcblist_pend_cbs(rsclp))
-		return; /* Nothing to do. */
-	*rclp->tail = *rsclp->tails[RCU_DONE_TAIL];
-	rclp->tail = rsclp->tails[RCU_NEXT_TAIL];
-	*rsclp->tails[RCU_DONE_TAIL] = NULL;
-	for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++)
-		rsclp->tails[i] = rsclp->tails[RCU_DONE_TAIL];
-}
-
-/*
- * Move the entire contents of the specified rcu_segcblist structure,
- * counts, callbacks, and all, to the specified rcu_cblist structure.
- * @@@ Why do we need this???  Moving early-boot CBs to NOCB lists?
- * @@@ Memory barrier needed?  (Not if only used at boot time...)
- */
-static inline void rcu_segcblist_extract_all(struct rcu_segcblist *rsclp,
-					     struct rcu_cblist *rclp)
-{
-	rcu_segcblist_extract_done_cbs(rsclp, rclp);
-	rcu_segcblist_extract_pend_cbs(rsclp, rclp);
-	rcu_segcblist_extract_count(rsclp, rclp);
-}
-
-/*
- * Insert counts from the specified rcu_cblist structure in the
- * specified rcu_segcblist structure.
- */
-static inline void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
-					      struct rcu_cblist *rclp)
-{
-	rsclp->len_lazy += rclp->len_lazy;
-	/* ->len sampled locklessly. */
-	WRITE_ONCE(rsclp->len, rsclp->len + rclp->len);
-	rclp->len_lazy = 0;
-	rclp->len = 0;
-}
-
-/*
- * Move callbacks from the specified rcu_cblist to the beginning of the
- * done-callbacks segment of the specified rcu_segcblist.
- */
-static inline void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
-						 struct rcu_cblist *rclp)
-{
-	int i;
-
-	if (!rclp->head)
-		return; /* No callbacks to move. */
-	*rclp->tail = rsclp->head;
-	rsclp->head = rclp->head;
-	for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
-		if (&rsclp->head == rsclp->tails[i])
-			rsclp->tails[i] = rclp->tail;
-		else
-			break;
-	rclp->head = NULL;
-	rclp->tail = &rclp->head;
-}
-
-/*
- * Move callbacks from the specified rcu_cblist to the end of the
- * new-callbacks segment of the specified rcu_segcblist.
- */
-static inline void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
-						 struct rcu_cblist *rclp)
-{
-	if (!rclp->head)
-		return; /* Nothing to do. */
-	*rsclp->tails[RCU_NEXT_TAIL] = rclp->head;
-	rsclp->tails[RCU_NEXT_TAIL] = rclp->tail;
-	rclp->head = NULL;
-	rclp->tail = &rclp->head;
-}
-
-/*
- * Advance the callbacks in the specified rcu_segcblist structure based
- * on the current value passed in for the grace-period counter.
- */
-static inline void rcu_segcblist_advance(struct rcu_segcblist *rsclp,
-					 unsigned long seq)
-{
-	int i, j;
-
-	WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
-	if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
-		return;
-
-	/*
-	 * Find all callbacks whose ->gp_seq numbers indicate that they
-	 * are ready to invoke, and put them into the RCU_DONE_TAIL segment.
-	 */
-	for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
-		if (ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
-			break;
-		rsclp->tails[RCU_DONE_TAIL] = rsclp->tails[i];
-	}
-
-	/* If no callbacks moved, nothing more need be done. */
-	if (i == RCU_WAIT_TAIL)
-		return;
-
-	/* Clean up tail pointers that might have been misordered above. */
-	for (j = RCU_WAIT_TAIL; j < i; j++)
-		rsclp->tails[j] = rsclp->tails[RCU_DONE_TAIL];
-
-	/*
-	 * Callbacks moved, so clean up the misordered ->tails[] pointers
-	 * that now point into the middle of the list of ready-to-invoke
-	 * callbacks.  The overall effect is to copy down the later pointers
-	 * into the gap that was created by the now-ready segments.
-	 */
-	for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
-		if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL])
-			break;  /* No more callbacks. */
-		rsclp->tails[j] = rsclp->tails[i];
-		rsclp->gp_seq[j] = rsclp->gp_seq[i];
-	}
-}
-
-/*
- * "Accelerate" callbacks based on more-accurate grace-period information.
- * The reason for this is that RCU does not synchronize the beginnings and
- * ends of grace periods, and that callbacks are posted locally.  This in
- * turn means that the callbacks must be labelled conservatively early
- * on, as getting exact information would degrade both performance and
- * scalability.  When more accurate grace-period information becomes
- * available, previously posted callbacks can be "accelerated", marking
- * them to complete at the end of the earlier grace period.
- *
- * This function operates on an rcu_segcblist structure, and also the
- * grace-period sequence number seq at which new callbacks would become
- * ready to invoke.  Returns true if there are callbacks that won't be
- * ready to invoke until seq, false otherwise.
- */
-static inline bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp,
-					    unsigned long seq)
-{
-	int i;
-
-	WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
-	if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
-		return false;
-
-	/*
-	 * Find the segment preceding the oldest segment of callbacks
-	 * whose ->gp_seq[] completion is at or after that passed in via
-	 * "seq", skipping any empty segments.  This oldest segment, along
-	 * with any later segments, can be merged in with any newly arrived
-	 * callbacks in the RCU_NEXT_TAIL segment, and assigned "seq"
-	 * as their ->gp_seq[] grace-period completion sequence number.
-	 */
-	for (i = RCU_NEXT_READY_TAIL; i > RCU_DONE_TAIL; i--)
-		if (rsclp->tails[i] != rsclp->tails[i - 1] &&
-		    ULONG_CMP_LT(rsclp->gp_seq[i], seq))
-			break;
-
-	/*
-	 * If all the segments contain callbacks that correspond to
-	 * earlier grace-period sequence numbers than "seq", leave.
-	 * Assuming that the rcu_segcblist structure has enough
-	 * segments in its arrays, this can only happen if some of
-	 * the non-done segments contain callbacks that really are
-	 * ready to invoke.  This situation will get straightened
-	 * out by the next call to rcu_segcblist_advance().
-	 *
-	 * Also advance to the oldest segment of callbacks whose
-	 * ->gp_seq[] completion is at or after that passed in via "seq",
-	 * skipping any empty segments.
-	 */
-	if (++i >= RCU_NEXT_TAIL)
-		return false;
-
-	/*
-	 * Merge all later callbacks, including newly arrived callbacks,
-	 * into the segment located by the for-loop above.  Assign "seq"
-	 * as the ->gp_seq[] value in order to correctly handle the case
-	 * where there were no pending callbacks in the rcu_segcblist
-	 * structure other than in the RCU_NEXT_TAIL segment.
-	 */
-	for (; i < RCU_NEXT_TAIL; i++) {
-		rsclp->tails[i] = rsclp->tails[RCU_NEXT_TAIL];
-		rsclp->gp_seq[i] = seq;
-	}
-	return true;
-}
-
-/*
- * Scan the specified rcu_segcblist structure for callbacks that need
- * a grace period later than the one specified by "seq".  We don't look
- * at the RCU_DONE_TAIL or RCU_NEXT_TAIL segments because they don't
- * have a grace-period sequence number.
- */
-static inline bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp,
-						  unsigned long seq)
-{
-	int i;
-
-	for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
-		if (rsclp->tails[i - 1] != rsclp->tails[i] &&
-		    ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
-			return true;
-	return false;
-}
-
-/*
  * Interim function to return rcu_segcblist head pointer.  Longer term, the
  * rcu_segcblist will be used more pervasively, removing the need for this
  * function.
@@ -643,3 +149,34 @@ static inline struct rcu_head **rcu_segcblist_tail(struct rcu_segcblist *rsclp)
 	WARN_ON_ONCE(rcu_segcblist_empty(rsclp));
 	return rsclp->tails[RCU_NEXT_TAIL];
 }
+
+void rcu_segcblist_init(struct rcu_segcblist *rsclp);
+void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
+bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg);
+bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
+bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
+struct rcu_head *rcu_segcblist_dequeue(struct rcu_segcblist *rsclp);
+void rcu_segcblist_dequeued_lazy(struct rcu_segcblist *rsclp);
+struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
+struct rcu_head *rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp);
+bool rcu_segcblist_new_cbs(struct rcu_segcblist *rsclp);
+void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
+			   struct rcu_head *rhp, bool lazy);
+bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
+			   struct rcu_head *rhp, bool lazy);
+void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
+				 struct rcu_cblist *rclp);
+void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
+				    struct rcu_cblist *rclp);
+void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
+				    struct rcu_cblist *rclp);
+void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
+				struct rcu_cblist *rclp);
+void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
+				   struct rcu_cblist *rclp);
+void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
+				   struct rcu_cblist *rclp);
+void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq);
+bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq);
+bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp,
+				    unsigned long seq);