[PATCH rcu 03/20] srcu: Use ->srcu_gp_seq for rcutorture reader batch

[Boqun Feng]

From: "Paul E. McKenney" <paul...@kernel.org>

This commit stops using ->srcu_idx for rcutorture's reader-batch
consistency checking, using ->srcu_gp_seq instead.  This is a first
step towards a faster srcu_read_{,un}lock_lite() that avoids the array
accesses that use ->srcu_idx.

Signed-off-by: Paul E. McKenney <paul...@kernel.org>
Cc: Alexei Starovoitov <a...@kernel.org>
Cc: Andrii Nakryiko <and...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Kent Overstreet <kent.overstr...@linux.dev>
Cc: <b...@vger.kernel.org>
Signed-off-by: Boqun Feng <boqun.f...@gmail.com>
---
 kernel/rcu/rcutorture.c | 2 ++
 kernel/rcu/srcutree.c   | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index d26fb1d33ed9..1d2de50fb5d6 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -791,6 +791,7 @@ static struct rcu_torture_ops srcu_ops = {
        .readunlock     = srcu_torture_read_unlock,
        .readlock_held  = torture_srcu_read_lock_held,
        .get_gp_seq     = srcu_torture_completed,
+       .gp_diff        = rcu_seq_diff,
        .deferred_free  = srcu_torture_deferred_free,
        .sync           = srcu_torture_synchronize,
        .exp_sync       = srcu_torture_synchronize_expedited,
@@ -834,6 +835,7 @@ static struct rcu_torture_ops srcud_ops = {
        .readunlock     = srcu_torture_read_unlock,
        .readlock_held  = torture_srcu_read_lock_held,
        .get_gp_seq     = srcu_torture_completed,
+       .gp_diff        = rcu_seq_diff,
        .deferred_free  = srcu_torture_deferred_free,
        .sync           = srcu_torture_synchronize,
        .exp_sync       = srcu_torture_synchronize_expedited,
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index b83c74c4dcc0..e69ce9d59abf 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1675,7 +1675,7 @@ EXPORT_SYMBOL_GPL(srcu_barrier);
  */
 unsigned long srcu_batches_completed(struct srcu_struct *ssp)
 {
-       return READ_ONCE(ssp->srcu_idx);
+       return READ_ONCE(ssp->srcu_sup->srcu_gp_seq);
 }
 EXPORT_SYMBOL_GPL(srcu_batches_completed);
 
-- 
2.39.5 (Apple Git-154)