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tcp: tsq: remove one locked operation in tcp_wfree()

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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>
This commit is contained in:
Eric Dumazet
2016-12-03 11:14:51 -08:00
committed by David S. Miller
parent 40fc3423b9
commit 408f0a6c21
1 changed files with 10 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
net/ipv4/tcp_output.c
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@@ -860,6 +860,7 @@ void tcp_wfree(struct sk_buff *skb)
{ {
struct sock *sk = skb->sk; struct sock *sk = skb->sk;
struct tcp_sock *tp = tcp_sk(sk); struct tcp_sock *tp = tcp_sk(sk);
unsigned long flags, nval, oval;
int wmem; int wmem;
/* Keep one reference on sk_wmem_alloc. /* 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) if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current)
goto out; goto out;
if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) && for (oval = READ_ONCE(tp->tsq_flags);; oval = nval) {
!test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) {
unsigned long flags;
struct tsq_tasklet *tsq; 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 */ /* queue this socket to tasklet queue */
local_irq_save(flags); local_irq_save(flags);
tsq = this_cpu_ptr(&tsq_tasklet); tsq = this_cpu_ptr(&tsq_tasklet);