srcu: Add SRCU_READ_FLAVOR_FAST_UPDOWN CPP macro

This commit adds the SRCU_READ_FLAVOR_FAST_UPDOWN=0x8 macro
and adjusts rcutorture to make use of it.  In this commit, both
SRCU_READ_FLAVOR_FAST=0x4 and the new SRCU_READ_FLAVOR_FAST_UPDOWN
test SRCU-fast.  When the SRCU-fast-updown is added, the new
SRCU_READ_FLAVOR_FAST_UPDOWN macro will test it when passed to the
rcutorture.reader_flavor module parameter.

The old SRCU_READ_FLAVOR_FAST macro's value changed from 0x8 to 0x4.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: <bpf@vger.kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

Author: paulmckrcu

include/linux/srcu.h

@@ -56,13 +56,15 @@ int init_srcu_struct_fast(struct srcu_struct *ssp);
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
 /* Values for SRCU Tree srcu_data ->srcu_reader_flavor, but also used by rcutorture. */
-#define SRCU_READ_FLAVOR_NORMAL	0x1		// srcu_read_lock().
-#define SRCU_READ_FLAVOR_NMI	0x2		// srcu_read_lock_nmisafe().
-//				0x4		// SRCU-lite is no longer with us.
-#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_FAST) // All of the above.
-#define SRCU_READ_FLAVOR_SLOWGP	SRCU_READ_FLAVOR_FAST
+#define SRCU_READ_FLAVOR_NORMAL		0x1		// srcu_read_lock().
+#define SRCU_READ_FLAVOR_NMI		0x2		// srcu_read_lock_nmisafe().
+//					0x4		// SRCU-lite is no longer with us.
+#define SRCU_READ_FLAVOR_FAST		0x4		// srcu_read_lock_fast().
+#define SRCU_READ_FLAVOR_FAST_UPDOWN	0x8		// srcu_read_lock_fast().
+#define SRCU_READ_FLAVOR_ALL		(SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
+					 SRCU_READ_FLAVOR_FAST | SRCU_READ_FLAVOR_FAST_UPDOWN)
+						// All of the above.
+#define SRCU_READ_FLAVOR_SLOWGP		(SRCU_READ_FLAVOR_FAST | SRCU_READ_FLAVOR_FAST_UPDOWN)
 						// Flavors requiring synchronize_rcu()
 						// instead of smp_mb().
 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);

kernel/rcu/rcutorture.c

@@ -702,6 +702,8 @@ static void srcu_torture_init(void)
 	rcu_sync_torture_init();
 	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
 		srcu_ctlp = &srcu_ctlf;
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
+		srcu_ctlp = &srcu_ctlf;
 }
 
 static void srcu_get_gp_data(int *flags, unsigned long *gp_seq)
@@ -728,6 +730,12 @@ static int srcu_torture_read_lock(void)
 		ret += idx << 1;
 	}
 	if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
+		scp = srcu_read_lock_fast(srcu_ctlp);
+		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
+		WARN_ON_ONCE(idx & ~0x1);
+		ret += idx << 2;
+	}
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN) {
 		scp = srcu_read_lock_fast(srcu_ctlp);
 		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
 		WARN_ON_ONCE(idx & ~0x1);
@@ -758,8 +766,10 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 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)
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
 		srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+		srcu_read_unlock_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 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))
@@ -793,7 +803,7 @@ static int srcu_torture_down_read(void)
 		WARN_ON_ONCE(idx & ~0x1);
 		return idx;
 	}
-	if (reader_flavor & SRCU_READ_FLAVOR_FAST) {
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN) {
 		scp = srcu_down_read_fast(srcu_ctlp);
 		idx = __srcu_ptr_to_ctr(srcu_ctlp, scp);
 		WARN_ON_ONCE(idx & ~0x1);
@@ -806,7 +816,7 @@ static int srcu_torture_down_read(void)
 static void srcu_torture_up_read(int idx)
 {
 	WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
-	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
 		srcu_up_read_fast(srcu_ctlp, __srcu_ctr_to_ptr(srcu_ctlp, (idx & 0x8) >> 3));
 	else if ((reader_flavor & SRCU_READ_FLAVOR_NORMAL) ||
 		 !(reader_flavor & SRCU_READ_FLAVOR_ALL))
@@ -901,14 +911,16 @@ static struct rcu_torture_ops srcu_ops = {
 	.no_pi_lock	= IS_ENABLED(CONFIG_TINY_SRCU),
 	.debug_objects	= 1,
 	.have_up_down	= IS_ENABLED(CONFIG_TINY_SRCU)
-				? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
+				? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST_UPDOWN,
 	.name		= "srcu"
 };
 
 static void srcud_torture_init(void)
 {
 	rcu_sync_torture_init();
-	if (reader_flavor & SRCU_READ_FLAVOR_FAST)
+	if (reader_flavor & SRCU_READ_FLAVOR_FAST_UPDOWN)
+		WARN_ON(init_srcu_struct_fast(&srcu_ctld));
+	else if (reader_flavor & SRCU_READ_FLAVOR_FAST)
 		WARN_ON(init_srcu_struct_fast(&srcu_ctld));
 	else
 		WARN_ON(init_srcu_struct(&srcu_ctld));
@@ -953,7 +965,7 @@ static struct rcu_torture_ops srcud_ops = {
 	.no_pi_lock	= IS_ENABLED(CONFIG_TINY_SRCU),
 	.debug_objects	= 1,
 	.have_up_down	= IS_ENABLED(CONFIG_TINY_SRCU)
-				? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST,
+				? 0 : SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_FAST_UPDOWN,
 	.name		= "srcud"
 };