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Commit 408f0a6c authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 40fc3423

net/ipv4/tcp_output.c

+10 −3
Original line number Diff line number Diff line
@@ -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);