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netpoll: more efficient locking

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Callers of netpoll_poll_lock() own NAPI_STATE_SCHED

Callers of netpoll_poll_unlock() have BH blocked between
the NAPI_STATE_SCHED being cleared and poll_lock is released.

We can avoid the spinlock which has no contention, and use cmpxchg()
on poll_owner which we need to set anyway.

This removes a possible lockdep violation after the cited commit,
since sk_busy_loop() re-enables BH before calling busy_poll_stop()

Fixes: 217f697436 ("net: busy-poll: allow preemption in sk_busy_loop()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2016-11-16 14:54:50 -08:00 • committed by David S. Miller
parent 1629dd4f76
commit 89c4b442b7
4 changed files with 10 additions and 11 deletions
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1
include/linux/netdevice.h
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@ -316,7 +316,6 @@ struct napi_struct {
unsigned int gro_count;
int (*poll)(struct napi_struct *, int);
#ifdef CONFIG_NETPOLL
spinlock_t poll_lock;
int poll_owner;
#endif
struct net_device *dev;