rcutorture: Remove support for SRCU-lite

Because SRCU-lite is being replaced by SRCU-fast, this commit removes
support for SRCU-lite from rcutorture.c

Both SRCU-lite and SRCU-fast provide faster readers by dropping the
smp_mb() call from their lock and unlock primitives, but incur a pair
of added RCU grace periods during the SRCU grace period.  There is a
trivial mapping from the SRCU-lite API to that of SRCU-fast, so there
should be no transition issues.

[ paulmck: Apply Christoph Hellwig feedback. ]

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>

Author: paulmckrcu

include/linux/srcu.h

@@ -49,7 +49,7 @@ int init_srcu_struct(struct srcu_struct *ssp);
 #define SRCU_READ_FLAVOR_LITE	0x4		// srcu_read_lock_lite().
 #define SRCU_READ_FLAVOR_FAST	0x8		// srcu_read_lock_fast().
 #define SRCU_READ_FLAVOR_ALL   (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
-				SRCU_READ_FLAVOR_LITE | SRCU_READ_FLAVOR_FAST) // All of the above.
+				SRCU_READ_FLAVOR_FAST) // All of the above.
 #define SRCU_READ_FLAVOR_SLOWGP	(SRCU_READ_FLAVOR_LITE | SRCU_READ_FLAVOR_FAST)
 						// Flavors requiring synchronize_rcu()
 						// instead of smp_mb().

kernel/rcu/rcutorture.c

@@ -718,11 +718,6 @@ static int srcu_torture_read_lock(void)
 		WARN_ON_ONCE(idx & ~0x1);
 		ret += idx << 1;
 	}
-	if (reader_flavor & SRCU_READ_FLAVOR_LITE) {
-		idx = srcu_read_lock_lite(srcu_ctlp);
-		WARN_ON_ONCE(idx & ~0x1);
-		ret += idx << 2;
-	}
 	if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
 		scp = srcu_read_lock_fast(srcu_ctlp);
 		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
@@ -756,8 +751,6 @@ static void srcu_torture_read_unlock(int idx)
 	WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
 	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
 		srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
-	if (reader_flavor & SRCU_READ_FLAVOR_LITE)
-		srcu_read_unlock_lite(srcu_ctlp, (idx & 0x4) >> 2);
 	if (reader_flavor & SRCU_READ_FLAVOR_NMI)
 		srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1);
 	if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) || !(reader_flavor & SRCU_READ_FLAVOR_ALL))