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, 114 insertions, 0 deletions

diff --git a/include/net/dropreason-qdisc.h b/include/net/dropreason-qdisc.h
new file mode 100644
index 000000000..fb151cd31
--- /dev/null
+++ b/include/net/dropreason-qdisc.h
@@ -0,0 +1,114 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _LINUX_DROPREASON_QDISC_H
+#define _LINUX_DROPREASON_QDISC_H
+#include <net/dropreason.h>
+
+#define DEFINE_QDISC_DROP_REASON(FN, FNe)	\
+	FN(UNSPEC)			\
+	FN(GENERIC)			\
+	FN(OVERLIMIT)			\
+	FN(CONGESTED)			\
+	FN(MAXFLOWS)			\
+	FN(FLOOD_PROTECTION)		\
+	FN(BAND_LIMIT)		\
+	FN(HORIZON_LIMIT)		\
+	FN(FLOW_LIMIT)			\
+	FN(L4S_STEP_NON_ECN)		\
+	FNe(MAX)
+
+#undef FN
+#undef FNe
+#define FN(reason)	QDISC_DROP_##reason,
+#define FNe(reason)	QDISC_DROP_##reason
+
+/**
+ * enum qdisc_drop_reason - reason why a qdisc dropped a packet
+ *
+ * Qdisc-specific drop reasons for packet drops that occur within the
+ * traffic control (TC) queueing discipline layer. These reasons provide
+ * detailed diagnostics about why packets were dropped by various qdisc
+ * algorithms, enabling fine-grained monitoring and troubleshooting of
+ * queue behavior.
+ */
+enum qdisc_drop_reason {
+	/**
+	 * @QDISC_DROP_UNSPEC: unspecified/invalid qdisc drop reason.
+	 * Value 0 serves as analogous to SKB_NOT_DROPPED_YET for enum skb_drop_reason.
+	 * Used for catching zero-initialized drop_reason fields.
+	 */
+	QDISC_DROP_UNSPEC = 0,
+	/**
+	 * @__QDISC_DROP_REASON: subsystem base value for qdisc drop reasons
+	 */
+	__QDISC_DROP_REASON = SKB_DROP_REASON_SUBSYS_QDISC <<
+				SKB_DROP_REASON_SUBSYS_SHIFT,
+	/**
+	 * @QDISC_DROP_GENERIC: generic/default qdisc drop, used when no
+	 * more specific reason applies
+	 */
+	QDISC_DROP_GENERIC,
+	/**
+	 * @QDISC_DROP_OVERLIMIT: packet dropped because the qdisc queue
+	 * length exceeded its configured limit (sch->limit). This typically
+	 * indicates the queue is full and cannot accept more packets.
+	 */
+	QDISC_DROP_OVERLIMIT,
+	/**
+	 * @QDISC_DROP_CONGESTED: packet dropped due to active congestion
+	 * control algorithms (e.g., CoDel, PIE, RED) detecting network
+	 * congestion. The qdisc proactively dropped the packet to signal
+	 * congestion to the sender and prevent bufferbloat.
+	 */
+	QDISC_DROP_CONGESTED,
+	/**
+	 * @QDISC_DROP_MAXFLOWS: packet dropped because the qdisc's flow
+	 * tracking table is full and no free slots are available to allocate
+	 * for a new flow. This indicates flow table exhaustion in flow-based
+	 * qdiscs that maintain per-flow state (e.g., SFQ).
+	 */
+	QDISC_DROP_MAXFLOWS,
+	/**
+	 * @QDISC_DROP_FLOOD_PROTECTION: packet dropped by flood protection
+	 * mechanism detecting unresponsive flows (potential DoS/flood).
+	 * Used by qdiscs implementing probabilistic drop algorithms like
+	 * BLUE (e.g., CAKE's Cobalt AQM).
+	 */
+	QDISC_DROP_FLOOD_PROTECTION,
+	/**
+	 * @QDISC_DROP_BAND_LIMIT: packet dropped because the priority band's
+	 * limit was reached. Used by qdiscs with priority bands that have
+	 * per-band packet limits (e.g., FQ).
+	 */
+	QDISC_DROP_BAND_LIMIT,
+	/**
+	 * @QDISC_DROP_HORIZON_LIMIT: packet dropped because its timestamp
+	 * is too far in the future (beyond the configured horizon).
+	 * Used by qdiscs with time-based scheduling (e.g., FQ).
+	 */
+	QDISC_DROP_HORIZON_LIMIT,
+	/**
+	 * @QDISC_DROP_FLOW_LIMIT: packet dropped because an individual flow
+	 * exceeded its per-flow packet/depth limit. Used by FQ and SFQ qdiscs
+	 * to enforce per-flow fairness and prevent a single flow from
+	 * monopolizing queue resources.
+	 */
+	QDISC_DROP_FLOW_LIMIT,
+	/**
+	 * @QDISC_DROP_L4S_STEP_NON_ECN: DualPI2 qdisc dropped a non-ECN-capable
+	 * packet because the L4S queue delay exceeded the step threshold.
+	 * Since the packet cannot be ECN-marked, it must be dropped to signal
+	 * congestion. See RFC 9332 for the DualQ Coupled AQM step mechanism.
+	 */
+	QDISC_DROP_L4S_STEP_NON_ECN,
+	/**
+	 * @QDISC_DROP_MAX: the maximum of qdisc drop reasons, which
+	 * shouldn't be used as a real 'reason' - only for tracing code gen
+	 */
+	QDISC_DROP_MAX,
+};
+
+#undef FN
+#undef FNe
+
+#endif