/branches/18.06.1/target/linux/generic/backport-4.9/024-2-tcp-tsq-remove-one-locked-operation-in-tcp_wfree.patch |
@@ -0,0 +1,48 @@ |
From 408f0a6c21e124cc4f6c7aa370b38aa47e55428d Mon Sep 17 00:00:00 2001 |
From: Eric Dumazet <edumazet@google.com> |
Date: Sat, 3 Dec 2016 11:14:51 -0800 |
Subject: [PATCH 02/10] 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 <edumazet@google.com> |
Signed-off-by: David S. Miller <davem@davemloft.net> |
--- |
net/ipv4/tcp_output.c | 13 ++++++++++--- |
1 file changed, 10 insertions(+), 3 deletions(-) |
|
--- a/net/ipv4/tcp_output.c |
+++ b/net/ipv4/tcp_output.c |
@@ -865,6 +865,7 @@ 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. |
@@ -882,11 +883,17 @@ 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); |