From 408f0a6c21e124cc4f6c7aa370b38aa47e55428d Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 3 Dec 2016 11:14:51 -0800 Subject: [PATCH] tcp: tsq: remove one locked operation in tcp_wfree() Instead of atomically clear TSQ_THROTTLED and atomically set TSQ_QUEUED bits, use one cmpxchg() to perform a single locked operation. Since the following patch will also set TCP_TSQ_DEFERRED here, this cmpxchg() will make this addition free. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 8f0289b0fb24..4adaf8e1bb63 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -860,6 +860,7 @@ void tcp_wfree(struct sk_buff *skb) { struct sock *sk = skb->sk; struct tcp_sock *tp = tcp_sk(sk); + unsigned long flags, nval, oval; int wmem; /* Keep one reference on sk_wmem_alloc. @@ -877,11 +878,17 @@ void tcp_wfree(struct sk_buff *skb) if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current) goto out; - if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) && - !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) { - unsigned long flags; + for (oval = READ_ONCE(tp->tsq_flags);; oval = nval) { struct tsq_tasklet *tsq; + if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED)) + goto out; + + nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED; + nval = cmpxchg(&tp->tsq_flags, oval, nval); + if (nval != oval) + continue; + /* queue this socket to tasklet queue */ local_irq_save(flags); tsq = this_cpu_ptr(&tsq_tasklet); -- 2.20.1