[NET]: Add NAPI_STATE_DISABLE. (a0a46196) · Commits · 戴 / test

Create a bit to signal that a napi_disable() is in progress. This sets up infrastructure such that net_rx_action() can generically break out of the ->poll() loop on a NAPI context that has a pending napi_disable() yet is being bombed with packets (and thus would otherwise poll endlessly and not allow the napi_disable() to finish). Now, what napi_disable() does is first set the NAPI_STATE_DISABLE bit (to indicate that a disable is pending), then it polls for the NAPI_STATE_SCHED bit, and once the NAPI_STATE_SCHED bit is acquired the NAPI_STATE_DISABLE bit is cleared. Here, the test_and_set_bit() provides the necessary memory barrier between the various bitops. napi_schedule_prep() now tests for a pending disable as it's first action and won't try to obtain the NAPI_STATE_SCHED bit if a disable is pending. As a result, we can remove the netif_running() check in netif_rx_schedule_prep() because the NAPI disable pending state serves this purpose. And, it does so in a NAPI centric manner which is what we really want. Signed-off-by:

David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

+13 −3

Original line number	Diff line number	Diff line
		@@ -319,21 +319,29 @@ struct napi_struct {
		enum
		{
		NAPI_STATE_SCHED, /* Poll is scheduled */
		NAPI_STATE_DISABLE, /* Disable pending */
		};

		extern void FASTCALL(__napi_schedule(struct napi_struct *n));

		static inline int napi_disable_pending(struct napi_struct *n)
		{
		return test_bit(NAPI_STATE_DISABLE, &n->state);
		}

		/**
		* napi_schedule_prep - check if napi can be scheduled
		* @n: napi context
		*
		* Test if NAPI routine is already running, and if not mark
		* it as running. This is used as a condition variable
		* insure only one NAPI poll instance runs
		* insure only one NAPI poll instance runs. We also make
		* sure there is no pending NAPI disable.
		*/
		static inline int napi_schedule_prep(struct napi_struct *n)
		{
		return !test_and_set_bit(NAPI_STATE_SCHED, &n->state);
		return !napi_disable_pending(n) &&
		!test_and_set_bit(NAPI_STATE_SCHED, &n->state);
		}

		/**
		@@ -389,8 +397,10 @@ static inline void napi_complete(struct napi_struct *n)
		*/
		static inline void napi_disable(struct napi_struct *n)
		{
		set_bit(NAPI_STATE_DISABLE, &n->state);
		while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
		msleep(1);
		clear_bit(NAPI_STATE_DISABLE, &n->state);
		}

		/**
		@@ -1268,7 +1278,7 @@ static inline u32 netif_msg_init(int debug_value, int default_msg_enable_bits)
		static inline int netif_rx_schedule_prep(struct net_device *dev,
		struct napi_struct *napi)
		{
		return netif_running(dev) && napi_schedule_prep(napi);
		return napi_schedule_prep(napi);
		}

		/* Add interface to tail of rx poll list. This assumes that _prep has

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