From 89c4b442b78bdba388337cc746fe63caba85f46c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 16 Nov 2016 14:54:50 -0800 Subject: netpoll: more efficient locking 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: 217f69743681 ("net: busy-poll: allow preemption in sk_busy_loop()") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/netpoll.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'net/core/netpoll.c') diff --git a/net/core/netpoll.c b/net/core/netpoll.c index 53599bd0c82d..9424673009c1 100644 --- a/net/core/netpoll.c +++ b/net/core/netpoll.c @@ -171,12 +171,12 @@ static void poll_one_napi(struct napi_struct *napi) static void poll_napi(struct net_device *dev) { struct napi_struct *napi; + int cpu = smp_processor_id(); list_for_each_entry(napi, &dev->napi_list, dev_list) { - if (napi->poll_owner != smp_processor_id() && - spin_trylock(&napi->poll_lock)) { + if (cmpxchg(&napi->poll_owner, -1, cpu) == -1) { poll_one_napi(napi); - spin_unlock(&napi->poll_lock); + smp_store_release(&napi->poll_owner, -1); } } } -- cgit v1.2.3-59-g8ed1b