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[NET]: Add NAPI_STATE_DISABLE.

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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>
This commit is contained in:
David S. Miller 2008-01-07 20:35:07 -08:00
parent bdb95b1792
commit a0a46196cd
1 changed files with 13 additions and 3 deletions
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16
include/linux/netdevice.h
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@ -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