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| author | Eric Dumazet <eric.dumazet@gmail.com> | 2012-01-28 16:11:03 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-01-30 12:45:07 -0500 |
| commit | 6f01fd6e6f6809061b56e78f1e8d143099716d70 (patch) | |
| tree | bd6b09a01a5f1af65fc12c6ac533f2b1f4caa777 /net | |
| parent | 5b35e1e6e9ca651e6b291c96d1106043c9af314a (diff) | |
| download | linux-6f01fd6e6f6809061b56e78f1e8d143099716d70.tar.gz | |
af_unix: fix EPOLLET regression for stream sockets
Commit 0884d7aa24 (AF_UNIX: Fix poll blocking problem when reading from a stream socket) added a regression for epoll() in Edge Triggered mode (EPOLLET) Appropriate fix is to use skb_peek()/skb_unlink() instead of skb_dequeue(), and only call skb_unlink() when skb is fully consumed. This remove the need to requeue a partial skb into sk_receive_queue head and the extra sk->sk_data_ready() calls that added the regression. This is safe because once skb is given to sk_receive_queue, it is not modified by a writer, and readers are serialized by u->readlock mutex. This also reduce number of spinlock acquisition for small reads or MSG_PEEK users so should improve overall performance. Reported-by: Nick Mathewson <nickm@freehaven.net> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: Alexey Moiseytsev <himeraster@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/unix/af_unix.c | 19 |
1 files changed, 4 insertions, 15 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index aad8fb699989..85d3bb7490aa 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1918,7 +1918,7 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, struct sk_buff *skb; unix_state_lock(sk); - skb = skb_dequeue(&sk->sk_receive_queue); + skb = skb_peek(&sk->sk_receive_queue); if (skb == NULL) { unix_sk(sk)->recursion_level = 0; if (copied >= target) @@ -1958,11 +1958,8 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, if (check_creds) { /* Never glue messages from different writers */ if ((UNIXCB(skb).pid != siocb->scm->pid) || - (UNIXCB(skb).cred != siocb->scm->cred)) { - skb_queue_head(&sk->sk_receive_queue, skb); - sk->sk_data_ready(sk, skb->len); + (UNIXCB(skb).cred != siocb->scm->cred)) break; - } } else { /* Copy credentials */ scm_set_cred(siocb->scm, UNIXCB(skb).pid, UNIXCB(skb).cred); @@ -1977,8 +1974,6 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, chunk = min_t(unsigned int, skb->len, size); if (memcpy_toiovec(msg->msg_iov, skb->data, chunk)) { - skb_queue_head(&sk->sk_receive_queue, skb); - sk->sk_data_ready(sk, skb->len); if (copied == 0) copied = -EFAULT; break; @@ -1993,13 +1988,10 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, if (UNIXCB(skb).fp) unix_detach_fds(siocb->scm, skb); - /* put the skb back if we didn't use it up.. */ - if (skb->len) { - skb_queue_head(&sk->sk_receive_queue, skb); - sk->sk_data_ready(sk, skb->len); + if (skb->len) break; - } + skb_unlink(skb, &sk->sk_receive_queue); consume_skb(skb); if (siocb->scm->fp) @@ -2010,9 +2002,6 @@ static int unix_stream_recvmsg(struct kiocb *iocb, struct socket *sock, if (UNIXCB(skb).fp) siocb->scm->fp = scm_fp_dup(UNIXCB(skb).fp); - /* put message back and return */ - skb_queue_head(&sk->sk_receive_queue, skb); - sk->sk_data_ready(sk, skb->len); break; } } while (size); |