[PATCH v2 8/8] rcutorture: Add atomic SRCU cross-CPU IRQ context mismatch test

["Paul E. McKenney" <paulmck@kernel.org>]

From: Kunwu Chan <kunwu.chan@gmail.com>

Add testtype 7 to verify that lockdep detects an IRQ-context
mismatch when an atomic SRCU read-side critical section is held
with IRQs enabled on one CPU and synchronize_srcu_atomic() is
called from an IPI handler on another CPU.

This covers the cross-CPU case that cannot be detected by
checking the current task's held locks.

Co-developed-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Zqiang <qiang.zhang@linux.dev>
Signed-off-by: Kunwu Chan <kunwu.chan@gmail.com>
Acked-by: Boqun Feng <boqun@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcutorture.c                       | 27 +++++++++++++-
 .../selftests/rcutorture/bin/srcu_lockdep.sh  | 36 +++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 35dc61d871b98..968343be4e0d1 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -4695,6 +4695,8 @@ DEFINE_STATIC_SRCU_ATOMIC(srcu7_atomic);
 DEFINE_STATIC_SRCU_ATOMIC(srcu8_atomic);
 DEFINE_STATIC_SRCU_ATOMIC(srcu9_atomic);
 
+DEFINE_STATIC_SRCU_ATOMIC(srcu_irq);
+
 static int srcu_lockdep_next(const char *f, const char *fl, const char *fs, const char *fu, int i,
 			     int cyclelen, int deadlock)
 {
@@ -4709,6 +4711,11 @@ static int srcu_lockdep_next(const char *f, const char *fl, const char *fs, cons
 	return j;
 }
 
+static void srcu_sync_irq(void *unused)
+{
+	synchronize_srcu_atomic(&srcu_irq);
+}
+
 // Test lockdep on SRCU-based deadlock scenarios.
 static void rcu_torture_init_srcu_lockdep(void)
 {
@@ -4892,13 +4899,31 @@ static void rcu_torture_init_srcu_lockdep(void)
 		return;
 	}
 
+	if (testtype == 7) {
+		int cpu;
+
+		for (i = 0; i < cyclelen; i++) {
+			idx = srcu_read_lock_atomic(&srcu_irq);
+			cpu = cpumask_any_but(cpu_online_mask,
+					      smp_processor_id());
+			if (cpu < nr_cpu_ids) {
+				pr_info("%s: CPU%d sending IPI to CPU%d\n",
+					__func__, smp_processor_id(), cpu);
+				smp_call_function_single(cpu, srcu_sync_irq,
+					NULL, 1);
+			}
+			srcu_read_unlock_atomic(&srcu_irq, idx);
+		}
+		return;
+	}
+
 err_out:
 	pr_info("%s: test_srcu_lockdep = %05d does nothing.\n", __func__, test_srcu_lockdep);
 	pr_info("%s: test_srcu_lockdep = DNNL.\n", __func__);
 	pr_info("%s: D: Deadlock if nonzero.\n", __func__);
 	pr_info("%s: NN: Test number, 0=SRCU, 1=SRCU/mutex, 2=SRCU/rwsem, 3=SRCU/Tasks Trace RCU, 4=SRCU_ATOMIC, ",
 		__func__);
-	pr_cont("5=SRCU_ATOMIC/raw_spinlock, 6=synchronize_srcu_atomic inside rcu_read_lock.\n");
+	pr_cont("5=SRCU_ATOMIC/raw_spinlock, 6=synchronize_srcu_atomic inside rcu_read_lock, 7=atomic SRCU cross-CPU IRQ context mismatch.\n");
 	pr_info("%s: L: Cycle length.\n", __func__);
 	if (!IS_ENABLED(CONFIG_TASKS_TRACE_RCU))
 		pr_info("%s: NN=3 disallowed because kernel is built with CONFIG_TASKS_TRACE_RCU=n\n", __func__);
diff --git a/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
index 3acaffe52c784..c29a39f7d8914 100755
--- a/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
+++ b/tools/testing/selftests/rcutorture/bin/srcu_lockdep.sh
@@ -115,6 +115,42 @@ do
 	fi
 done
 
+# Verify that synchronize_srcu_atomic() detects IRQ context mismatch
+# when SRCU reader previously ran with IRQs enabled.
+for c in 1 2 3
+do
+	err=
+	val=$((1000+7*10+c))
+	tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 5s \
+		--configs "SRCU-P" \
+		--kconfig "CONFIG_FORCE_NEED_SRCU_NMI_SAFE=y" \
+		--bootargs "rcutorture.test_srcu_lockdep=$val" \
+		--trust-make --datestamp "$ds/$val" > "$T/kvm.sh.out" 2>&1
+	ret=$?
+	mv "$T/kvm.sh.out" "$RCUTORTURE/res/$ds/$val"
+	if ! grep -q '^CONFIG_PROVE_LOCKING=y' .config
+	then
+		echo "rcu_torture_init_srcu_lockdep:Error: CONFIG_PROVE_LOCKING" \
+				"disabled in rcutorture SRCU-P scenario"
+		err=1
+	fi
+	if test "$ret" -eq 0
+	then
+		err=1
+		echo -n Missing lockdep warning for > "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+	elif ! grep -q "inconsistent {HARDIRQ-ON-R}" "$RCUTORTURE/res/$ds/$val/SRCU-P/console.log"
+	then
+		err=1
+		echo -n Missing lockdep warning for > "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+	fi
+	if test -n "$err"
+	then
+		grep "rcu_torture_init_srcu_lockdep: test_srcu_lockdep = " "$RCUTORTURE/res/$ds/$val/SRCU-P/console.log" | sed -e 's/^.*rcu_torture_init_srcu_lockdep://' >> "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+		cat "$RCUTORTURE/res/$ds/$val/kvm.sh.err"
+		nerrs=$((nerrs+1))
+	fi
+done
+
 # Test lockdep-enabled testing of mixed SRCU readers.
 for val in 0x1 0xf
 do
-- 
2.40.1