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SUNRPC: Avoid spurious wake-up during UDP connect processing

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To clear out old state, the UDP connect workers unconditionally invoke
xs_close() before proceeding with a new connect.  Nowadays this causes
a spurious wake-up of the task waiting for the connect to complete.

This is a little racey, but usually harmless.  The waiting task
immediately retries the connect via a call_bind/call_connect sequence,
which usually finds the transport already in the connected state
because the connect worker has finished in the background.

To avoid a spurious wake-up, factor the xs_close() logic that resets
the underlying socket into a helper, and have the UDP connect workers
call that helper instead of xs_close().

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Chuck Lever 2009-03-11 14:10:21 -04:00 committed by Trond Myklebust
parent 01d37c428a
commit fe315e76fc
1 changed files with 26 additions and 18 deletions
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44
net/sunrpc/xprtsock.c
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@ -767,23 +767,13 @@ static void xs_restore_old_callbacks(struct sock_xprt *transport, struct sock *s
sk->sk_error_report = transport->old_error_report;
}
/**
* xs_close - close a socket
* @xprt: transport
*
* This is used when all requests are complete; ie, no DRC state remains
* on the server we want to save.
*/
static void xs_close(struct rpc_xprt *xprt)
static void xs_reset_transport(struct sock_xprt *transport)
{
struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
struct socket *sock = transport->sock;
struct sock *sk = transport->inet;
if (!sk)
goto clear_close_wait;
dprintk("RPC: xs_close xprt %p\n", xprt);
if (sk == NULL)
return;
write_lock_bh(&sk->sk_callback_lock);
transport->inet = NULL;
@ -797,7 +787,23 @@ static void xs_close(struct rpc_xprt *xprt)
sk->sk_no_check = 0;
sock_release(sock);
clear_close_wait:
}
/**
* xs_close - close a socket
* @xprt: transport
*
* This is used when all requests are complete; ie, no DRC state remains
* on the server we want to save.
*/
static void xs_close(struct rpc_xprt *xprt)
{
struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
dprintk("RPC: xs_close xprt %p\n", xprt);
xs_reset_transport(transport);
smp_mb__before_clear_bit();
clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
clear_bit(XPRT_CLOSING, &xprt->state);
@ -1537,9 +1543,10 @@ static void xs_udp_connect_worker4(struct work_struct *work)
goto out;
/* Start by resetting any existing state */
xs_close(xprt);
xs_reset_transport(transport);
if ((err = sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock)) < 0) {
err = sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock);
if (err < 0) {
dprintk("RPC: can't create UDP transport socket (%d).\n", -err);
goto out;
}
@ -1578,9 +1585,10 @@ static void xs_udp_connect_worker6(struct work_struct *work)
goto out;
/* Start by resetting any existing state */
xs_close(xprt);
xs_reset_transport(transport);
if ((err = sock_create_kern(PF_INET6, SOCK_DGRAM, IPPROTO_UDP, &sock)) < 0) {
err = sock_create_kern(PF_INET6, SOCK_DGRAM, IPPROTO_UDP, &sock);
if (err < 0) {
dprintk("RPC: can't create UDP transport socket (%d).\n", -err);
goto out;
}