rcutorture: Add reader_flavor parameter for SRCU readers

This commit adds an rcutorture.reader_flavor parameter whose bits
correspond to reader flavors.  For example, SRCU's readers are 0x1 for
normal and 0x2 for NMI-safe.

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: <[email protected]>
Reviewed-by: Neeraj Upadhyay <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>

Author: paulmckrcu

Documentation/admin-guide/kernel-parameters.txt

@@ -5426,6 +5426,14 @@
 			The delay, in seconds, between successive
 			read-then-exit testing episodes.
 
+	rcutorture.reader_flavor= [KNL]
+			A bit mask indicating which readers to use.
+			If there is more than one bit set, the readers
+			are entered from low-order bit up, and are
+			exited in the opposite order.  For SRCU, the
+			0x1 bit is normal readers and the 0x2 bit is
+			for NMI-safe readers.
+
 	rcutorture.shuffle_interval= [KNL]
 			Set task-shuffle interval (s).  Shuffling tasks
 			allows some CPUs to go into dyntick-idle mode

kernel/rcu/rcutorture.c

@@ -111,6 +111,7 @@ torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disab
 torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
 torture_param(int, read_exit_delay, 13, "Delay between read-then-exit episodes (s)");
 torture_param(int, read_exit_burst, 16, "# of read-then-exit bursts per episode, zero to disable");
+torture_param(int, reader_flavor, 0x1, "Reader flavors to use, one per bit.");
 torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
 torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
 torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
@@ -644,10 +645,20 @@ static void srcu_get_gp_data(int *flags, unsigned long *gp_seq)
 
 static int srcu_torture_read_lock(void)
 {
-	if (cur_ops == &srcud_ops)
-		return srcu_read_lock_nmisafe(srcu_ctlp);
-	else
-		return srcu_read_lock(srcu_ctlp);
+	int idx;
+	int ret = 0;
+
+	if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) {
+		idx = srcu_read_lock(srcu_ctlp);
+		WARN_ON_ONCE(idx & ~0x1);
+		ret += idx;
+	}
+	if (reader_flavor & 0x2) {
+		idx = srcu_read_lock_nmisafe(srcu_ctlp);
+		WARN_ON_ONCE(idx & ~0x1);
+		ret += idx << 1;
+	}
+	return ret;
 }
 
 static void
@@ -671,10 +682,11 @@ srcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
 
 static void srcu_torture_read_unlock(int idx)
 {
-	if (cur_ops == &srcud_ops)
-		srcu_read_unlock_nmisafe(srcu_ctlp, idx);
-	else
-		srcu_read_unlock(srcu_ctlp, idx);
+	WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor && (idx & ~0x1)));
+	if (reader_flavor & 0x2)
+		srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1);
+	if ((reader_flavor & 0x1) || !(reader_flavor & 0x7))
+		srcu_read_unlock(srcu_ctlp, idx & 0x1);
 }
 
 static int torture_srcu_read_lock_held(void)
@@ -2389,6 +2401,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 "n_barrier_cbs=%d "
 		 "onoff_interval=%d onoff_holdoff=%d "
 		 "read_exit_delay=%d read_exit_burst=%d "
+		 "reader_flavor=%x "
 		 "nocbs_nthreads=%d nocbs_toggle=%d "
 		 "test_nmis=%d\n",
 		 torture_type, tag, nrealreaders, nfakewriters,
@@ -2401,6 +2414,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
 		 n_barrier_cbs,
 		 onoff_interval, onoff_holdoff,
 		 read_exit_delay, read_exit_burst,
+		 reader_flavor,
 		 nocbs_nthreads, nocbs_toggle,
 		 test_nmis);
 }