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Commit a0a46196 authored by David S. Miller's avatar David S. Miller
Browse files

[NET]: Add NAPI_STATE_DISABLE. 



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: default avatarDavid S. Miller <davem@davemloft.net>
parent bdb95b17

include/linux/netdevice.h

+13 −3
Original line number Original line Diff line number Diff line
@@ -319,21 +319,29 @@ struct napi_struct { 
enum

enum

{

{

	NAPI_STATE_SCHED,	/* Poll is scheduled */

	NAPI_STATE_SCHED,	/* Poll is scheduled */

	NAPI_STATE_DISABLE,	/* Disable pending */

};

};





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

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

 *	napi_schedule_prep - check if napi can be scheduled

 *	@n: napi context

 *	@n: napi context

 *

 *

 * Test if NAPI routine is already running, and if not mark

 * Test if NAPI routine is already running, and if not mark

 * it as running.  This is used as a condition variable

 * 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)

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)

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))

	while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))

		msleep(1);

		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,

static inline int netif_rx_schedule_prep(struct net_device *dev,

					 struct napi_struct *napi)

					 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

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