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rcu/segcblist: Factor out rcu_segcblist_advance_compact() helper

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This commit extracts the tail-pointer cleanup and segment compaction
logic from rcu_segcblist_advance() into a new static helper function,
rcu_segcblist_advance_compact(). This shared logic will be reused by the
upcoming srcu_segcblist_advance() standalone implementation, which
cannot call the core rcu_segcblist_advance() because that function will
use RCU-specific globals.

No functional change.

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Puranjay Mohan 2026-06-24 06:23:45 -07:00 committed by Paul E. McKenney
parent ca1f962a82
commit 97b4c6b933
1 changed files with 32 additions and 18 deletions
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50
kernel/rcu/rcu_segcblist.c
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@ -462,13 +462,43 @@ void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], rclp->tail);
}
/*
* Clean up and compact the segmented callback list after callbacks have been
* advanced to the RCU_DONE_TAIL segment. The @i parameter is the index of the
* first segment that was NOT advanced (i.e., the segment after the last one
* moved to RCU_DONE_TAIL). This function fixes up tail pointers and compacts
* any gaps left by the moved segments.
*/
static void rcu_segcblist_advance_compact(struct rcu_segcblist *rsclp, int i)
{
int j;
/* Clean up tail pointers that might have been misordered above. */
for (j = RCU_WAIT_TAIL; j < i; j++)
WRITE_ONCE(rsclp->tails[j], rsclp->tails[RCU_DONE_TAIL]);
/*
* Callbacks moved, so there might be an empty RCU_WAIT_TAIL
* and a non-empty RCU_NEXT_READY_TAIL. If so, copy the
* RCU_NEXT_READY_TAIL segment to fill the RCU_WAIT_TAIL gap
* created by the now-ready-to-invoke 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. */
WRITE_ONCE(rsclp->tails[j], rsclp->tails[i]);
rcu_segcblist_move_seglen(rsclp, i, j);
rsclp->gp_seq[j] = rsclp->gp_seq[i];
}
}
/*
* Advance the callbacks in the specified rcu_segcblist structure based
* on the current value passed in for the grace-period counter.
*/
void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
{
int i, j;
int i;
WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
@ -489,23 +519,7 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
if (i == RCU_WAIT_TAIL)
return;
/* Clean up tail pointers that might have been misordered above. */
for (j = RCU_WAIT_TAIL; j < i; j++)
WRITE_ONCE(rsclp->tails[j], rsclp->tails[RCU_DONE_TAIL]);
/*
* Callbacks moved, so there might be an empty RCU_WAIT_TAIL
* and a non-empty RCU_NEXT_READY_TAIL. If so, copy the
* RCU_NEXT_READY_TAIL segment to fill the RCU_WAIT_TAIL gap
* created by the now-ready-to-invoke 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. */
WRITE_ONCE(rsclp->tails[j], rsclp->tails[i]);
rcu_segcblist_move_seglen(rsclp, i, j);
rsclp->gp_seq[j] = rsclp->gp_seq[i];
}
rcu_segcblist_advance_compact(rsclp, i);
}
/*