linux-kernel - [PATCH tip/core/rcu 06/17] rcutorture: Make rcu_torture_fakewriter() use blocking wait primitives

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Date:   Wed,  6 Jan 2021 09:16:59 -0800
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH tip/core/rcu 06/17] rcutorture: Make rcu_torture_fakewriter() use blocking wait primitives

From: "Paul E. McKenney" <paulmck@...nel.org>

Full testing of the new SRCU polling API requires that the fake
writers also use it in order to test concurrent calls to all of the API
members, especially start_poll_synchronize_srcu().  This commit makes
rcu_torture_fakewriter() use all available blocking grace-period-wait
primitives available from the RCU flavor under test.

Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 kernel/rcu/rcutorture.c | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index ea44a2b..1b70aa4 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -1289,6 +1289,8 @@ rcu_torture_writer(void *arg)
 static int
 rcu_torture_fakewriter(void *arg)
 {
+	unsigned long gp_snap;
+	int i;
 	DEFINE_TORTURE_RANDOM(rand);
 
 	VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
@@ -1300,15 +1302,37 @@ rcu_torture_fakewriter(void *arg)
 		if (cur_ops->cb_barrier != NULL &&
 		    torture_random(&rand) % (nfakewriters * 8) == 0) {
 			cur_ops->cb_barrier();
-		} else if (gp_normal == gp_exp) {
-			if (cur_ops->sync && torture_random(&rand) & 0x80)
-				cur_ops->sync();
-			else if (cur_ops->exp_sync)
+		} else {
+			switch (synctype[torture_random(&rand) % nsynctypes]) {
+			case RTWS_DEF_FREE:
+				break;
+			case RTWS_EXP_SYNC:
 				cur_ops->exp_sync();
-		} else if (gp_normal && cur_ops->sync) {
-			cur_ops->sync();
-		} else if (cur_ops->exp_sync) {
-			cur_ops->exp_sync();
+				break;
+			case RTWS_COND_GET:
+				gp_snap = cur_ops->get_gp_state();
+				i = torture_random(&rand) % 16;
+				if (i != 0)
+					schedule_timeout_interruptible(i);
+				udelay(torture_random(&rand) % 1000);
+				cur_ops->cond_sync(gp_snap);
+				break;
+			case RTWS_POLL_GET:
+				gp_snap = cur_ops->start_gp_poll();
+				while (!cur_ops->poll_gp_state(gp_snap)) {
+					i = torture_random(&rand) % 16;
+					if (i != 0)
+						schedule_timeout_interruptible(i);
+					udelay(torture_random(&rand) % 1000);
+				}
+				break;
+			case RTWS_SYNC:
+				cur_ops->sync();
+				break;
+			default:
+				WARN_ON_ONCE(1);
+				break;
+			}
 		}
 		stutter_wait("rcu_torture_fakewriter");
 	} while (!torture_must_stop());
-- 
2.9.5