Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 173 insertions, 0 deletions

diff --git a/include/net/netdev_queues.h b/include/net/netdev_queues.h
new file mode 100644
index 0000000000..8b8ed4e13d
--- /dev/null
+++ b/include/net/netdev_queues.h
@@ -0,0 +1,173 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_NET_QUEUES_H
+#define _LINUX_NET_QUEUES_H
+
+#include <linux/netdevice.h>
+
+/**
+ * DOC: Lockless queue stopping / waking helpers.
+ *
+ * The netif_txq_maybe_stop() and __netif_txq_completed_wake()
+ * macros are designed to safely implement stopping
+ * and waking netdev queues without full lock protection.
+ *
+ * We assume that there can be no concurrent stop attempts and no concurrent
+ * wake attempts. The try-stop should happen from the xmit handler,
+ * while wake up should be triggered from NAPI poll context.
+ * The two may run concurrently (single producer, single consumer).
+ *
+ * The try-stop side is expected to run from the xmit handler and therefore
+ * it does not reschedule Tx (netif_tx_start_queue() instead of
+ * netif_tx_wake_queue()). Uses of the ``stop`` macros outside of the xmit
+ * handler may lead to xmit queue being enabled but not run.
+ * The waking side does not have similar context restrictions.
+ *
+ * The macros guarantee that rings will not remain stopped if there's
+ * space available, but they do *not* prevent false wake ups when
+ * the ring is full! Drivers should check for ring full at the start
+ * for the xmit handler.
+ *
+ * All descriptor ring indexes (and other relevant shared state) must
+ * be updated before invoking the macros.
+ */
+
+#define netif_txq_try_stop(txq, get_desc, start_thrs)			\
+	({								\
+		int _res;						\
+									\
+		netif_tx_stop_queue(txq);				\
+		/* Producer index and stop bit must be visible		\
+		 * to consumer before we recheck.			\
+		 * Pairs with a barrier in __netif_txq_completed_wake(). \
+		 */							\
+		smp_mb__after_atomic();					\
+									\
+		/* We need to check again in a case another		\
+		 * CPU has just made room available.			\
+		 */							\
+		_res = 0;						\
+		if (unlikely(get_desc >= start_thrs)) {			\
+			netif_tx_start_queue(txq);			\
+			_res = -1;					\
+		}							\
+		_res;							\
+	})								\
+
+/**
+ * netif_txq_maybe_stop() - locklessly stop a Tx queue, if needed
+ * @txq:	struct netdev_queue to stop/start
+ * @get_desc:	get current number of free descriptors (see requirements below!)
+ * @stop_thrs:	minimal number of available descriptors for queue to be left
+ *		enabled
+ * @start_thrs:	minimal number of descriptors to re-enable the queue, can be
+ *		equal to @stop_thrs or higher to avoid frequent waking
+ *
+ * All arguments may be evaluated multiple times, beware of side effects.
+ * @get_desc must be a formula or a function call, it must always
+ * return up-to-date information when evaluated!
+ * Expected to be used from ndo_start_xmit, see the comment on top of the file.
+ *
+ * Returns:
+ *	 0 if the queue was stopped
+ *	 1 if the queue was left enabled
+ *	-1 if the queue was re-enabled (raced with waking)
+ */
+#define netif_txq_maybe_stop(txq, get_desc, stop_thrs, start_thrs)	\
+	({								\
+		int _res;						\
+									\
+		_res = 1;						\
+		if (unlikely(get_desc < stop_thrs))			\
+			_res = netif_txq_try_stop(txq, get_desc, start_thrs); \
+		_res;							\
+	})								\
+
+/* Variant of netdev_tx_completed_queue() which guarantees smp_mb() if
+ * @bytes != 0, regardless of kernel config.
+ */
+static inline void
+netdev_txq_completed_mb(struct netdev_queue *dev_queue,
+			unsigned int pkts, unsigned int bytes)
+{
+	if (IS_ENABLED(CONFIG_BQL))
+		netdev_tx_completed_queue(dev_queue, pkts, bytes);
+	else if (bytes)
+		smp_mb();
+}
+
+/**
+ * __netif_txq_completed_wake() - locklessly wake a Tx queue, if needed
+ * @txq:	struct netdev_queue to stop/start
+ * @pkts:	number of packets completed
+ * @bytes:	number of bytes completed
+ * @get_desc:	get current number of free descriptors (see requirements below!)
+ * @start_thrs:	minimal number of descriptors to re-enable the queue
+ * @down_cond:	down condition, predicate indicating that the queue should
+ *		not be woken up even if descriptors are available
+ *
+ * All arguments may be evaluated multiple times.
+ * @get_desc must be a formula or a function call, it must always
+ * return up-to-date information when evaluated!
+ * Reports completed pkts/bytes to BQL.
+ *
+ * Returns:
+ *	 0 if the queue was woken up
+ *	 1 if the queue was already enabled (or disabled but @down_cond is true)
+ *	-1 if the queue was left unchanged (@start_thrs not reached)
+ */
+#define __netif_txq_completed_wake(txq, pkts, bytes,			\
+				   get_desc, start_thrs, down_cond)	\
+	({								\
+		int _res;						\
+									\
+		/* Report to BQL and piggy back on its barrier.		\
+		 * Barrier makes sure that anybody stopping the queue	\
+		 * after this point sees the new consumer index.	\
+		 * Pairs with barrier in netif_txq_try_stop().		\
+		 */							\
+		netdev_txq_completed_mb(txq, pkts, bytes);		\
+									\
+		_res = -1;						\
+		if (pkts && likely(get_desc >= start_thrs)) {		\
+			_res = 1;					\
+			if (unlikely(netif_tx_queue_stopped(txq)) &&	\
+			    !(down_cond)) {				\
+				netif_tx_wake_queue(txq);		\
+				_res = 0;				\
+			}						\
+		}							\
+		_res;							\
+	})
+
+#define netif_txq_completed_wake(txq, pkts, bytes, get_desc, start_thrs) \
+	__netif_txq_completed_wake(txq, pkts, bytes, get_desc, start_thrs, false)
+
+/* subqueue variants follow */
+
+#define netif_subqueue_try_stop(dev, idx, get_desc, start_thrs)		\
+	({								\
+		struct netdev_queue *txq;				\
+									\
+		txq = netdev_get_tx_queue(dev, idx);			\
+		netif_txq_try_stop(txq, get_desc, start_thrs);		\
+	})
+
+#define netif_subqueue_maybe_stop(dev, idx, get_desc, stop_thrs, start_thrs) \
+	({								\
+		struct netdev_queue *txq;				\
+									\
+		txq = netdev_get_tx_queue(dev, idx);			\
+		netif_txq_maybe_stop(txq, get_desc, stop_thrs, start_thrs); \
+	})
+
+#define netif_subqueue_completed_wake(dev, idx, pkts, bytes,		\
+				      get_desc, start_thrs)		\
+	({								\
+		struct netdev_queue *txq;				\
+									\
+		txq = netdev_get_tx_queue(dev, idx);			\
+		netif_txq_completed_wake(txq, pkts, bytes,		\
+					 get_desc, start_thrs);		\
+	})
+
+#endif