/* 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 voidnetdev_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