[PATCH rcu 12/12] refscale: Add srcu_read_lock_lite() support using "srcu-lite"

[Paul E. McKenney]

This commit creates a new srcu-lite option for the refscale.scale_type
module parameter that selects srcu_read_lock_lite() and
srcu_read_unlock_lite().

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>
---
 kernel/rcu/refscale.c | 51 +++++++++++++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 11 deletions(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index be66e5a67ee19..897d5b5494949 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -216,6 +216,36 @@ static const struct ref_scale_ops srcu_ops = {
        .name           = "srcu"
 };
 
+static void srcu_lite_ref_scale_read_section(const int nloops)
+{
+       int i;
+       int idx;
+
+       for (i = nloops; i >= 0; i--) {
+               idx = srcu_read_lock_lite(srcu_ctlp);
+               srcu_read_unlock_lite(srcu_ctlp, idx);
+       }
+}
+
+static void srcu_lite_ref_scale_delay_section(const int nloops, const int udl, 
const int ndl)
+{
+       int i;
+       int idx;
+
+       for (i = nloops; i >= 0; i--) {
+               idx = srcu_read_lock_lite(srcu_ctlp);
+               un_delay(udl, ndl);
+               srcu_read_unlock_lite(srcu_ctlp, idx);
+       }
+}
+
+static const struct ref_scale_ops srcu_lite_ops = {
+       .init           = rcu_sync_scale_init,
+       .readsection    = srcu_lite_ref_scale_read_section,
+       .delaysection   = srcu_lite_ref_scale_delay_section,
+       .name           = "srcu-lite"
+};
+
 #ifdef CONFIG_TASKS_RCU
 
 // Definitions for RCU Tasks ref scale testing: Empty read markers.
@@ -1133,27 +1163,26 @@ ref_scale_init(void)
        long i;
        int firsterr = 0;
        static const struct ref_scale_ops *scale_ops[] = {
-               &rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, 
&rwlock_ops,
-               &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, 
&sched_clock_ops, &clock_ops,
-               &jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops, 
&typesafe_seqlock_ops,
+               &rcu_ops, &srcu_ops, &srcu_lite_ops, RCU_TRACE_OPS RCU_TASKS_OPS
+               &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, 
&acqrel_ops,
+               &sched_clock_ops, &clock_ops, &jiffies_ops, &typesafe_ref_ops, 
&typesafe_lock_ops,
+               &typesafe_seqlock_ops,
        };
 
        if (!torture_init_begin(scale_type, verbose))
                return -EBUSY;
 
        for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
-               cur_ops = scale_ops[i];
-               if (strcmp(scale_type, cur_ops->name) == 0)
+               cur_ops = scale_ops[i]; if (strcmp(scale_type,
+               cur_ops->name) == 0)
                        break;
        }
        if (i == ARRAY_SIZE(scale_ops)) {
-               pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
-               pr_alert("rcu-scale types:");
-               for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
+               pr_alert("rcu-scale: invalid scale type: \"%s\"\n",
+               scale_type); pr_alert("rcu-scale types:"); for (i = 0;
+               i < ARRAY_SIZE(scale_ops); i++)
                        pr_cont(" %s", scale_ops[i]->name);
-               pr_cont("\n");
-               firsterr = -EINVAL;
-               cur_ops = NULL;
+               pr_cont("\n"); firsterr = -EINVAL; cur_ops = NULL;
                goto unwind;
        }
        if (cur_ops->init)
-- 
2.40.1