scftorture: Count single_rpc offline failures in statistics outputgrafted

scf_torture_stats_print() aggregates each invoker thread's counters
into a local scf_statistics structure before printing, but the
n_single_rpc_ofl field is missing from the aggregation loop.  As a
result, the "single_rpc_ofl" value printed in the statistics line is
always zero, even when smp_call_function_single() invocations for the
RPC test have failed due to offline CPUs and been counted by the
invoker threads.

Add the missing accumulation so that the printed value reflects the
actual counts.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/is_single_threaded.c b/lib/is_single_threaded.c
new file mode 100644
index 000000000..8c98b20bf
--- /dev/null
+++ b/lib/is_single_threaded.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Function to determine if a thread group is single threaded or not
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ * - Derived from security/selinux/hooks.c
+ */
+#include <linux/sched/signal.h>
+#include <linux/sched/task.h>
+#include <linux/sched/mm.h>
+
+/*
+ * Returns true if the task does not share ->mm with another thread/process.
+ */
+bool current_is_single_threaded(void)
+{
+	struct task_struct *task = current;
+	struct mm_struct *mm = task->mm;
+	struct task_struct *p, *t;
+	bool ret;
+
+	if (atomic_read(&task->signal->live) != 1)
+		return false;
+
+	if (atomic_read(&mm->mm_users) == 1)
+		return true;
+
+	ret = false;
+	rcu_read_lock();
+	for_each_process(p) {
+		if (unlikely(p->flags & PF_KTHREAD))
+			continue;
+		if (unlikely(p == task->group_leader))
+			continue;
+
+		for_each_thread(p, t) {
+			if (unlikely(t->mm == mm))
+				goto found;
+			if (likely(t->mm))
+				break;
+			/*
+			 * t->mm == NULL. Make sure next_thread/next_task
+			 * will see other CLONE_VM tasks which might be
+			 * forked before exiting.
+			 */
+			smp_rmb();
+		}
+	}
+	ret = true;
+found:
+	rcu_read_unlock();
+
+	return ret;
+}