Author: rmacklem
Date: Thu Jun 25 00:28:43 2009
New Revision: 194934
URL: http://svn.freebsd.org/changeset/base/194934
Log:
Fix two known problems in clnt_rc.c, plus issues w.r.t. smp noted
during reading of the code. Change the code so that it never accesses
rc_connecting, rc_closed or rc_client when the rc_lock mutex is not held.
Also, it now performs the CLNT_CLOSE(client) and CLNT_RELEASE(client)
calls after the rc_lock mutex has been released, since those calls do
msleep()s with another mutex held. Change clnt_reconnect_call() so that
releasing the reference count is delayed until after the
"if (rc->rc_client == client)" check, so that rc_client cannot have been
recycled.
Tested by: pho
Reviewed by: dfr
Approved by: kib (mentor)
Modified:
head/sys/rpc/clnt_rc.c
Modified: head/sys/rpc/clnt_rc.c
==============================================================================
--- head/sys/rpc/clnt_rc.c Thu Jun 25 00:14:27 2009 (r194933)
+++ head/sys/rpc/clnt_rc.c Thu Jun 25 00:28:43 2009 (r194934)
@@ -146,33 +146,33 @@ clnt_reconnect_connect(CLIENT *cl)
int error;
int one = 1;
struct ucred *oldcred;
+ CLIENT *newclient = NULL;
mtx_lock(&rc->rc_lock);
-again:
+ while (rc->rc_connecting) {
+ error = msleep(rc, &rc->rc_lock,
+ rc->rc_intr ? PCATCH : 0, "rpcrecon", 0);
+ if (error) {
+ mtx_unlock(&rc->rc_lock);
+ return (RPC_INTR);
+ }
+ }
if (rc->rc_closed) {
mtx_unlock(&rc->rc_lock);
return (RPC_CANTSEND);
}
- if (rc->rc_connecting) {
- while (!rc->rc_closed && !rc->rc_client && rc->rc_connecting) {
- error = msleep(rc, &rc->rc_lock,
- rc->rc_intr ? PCATCH : 0, "rpcrecon", 0);
- if (error) {
- mtx_unlock(&rc->rc_lock);
- return (RPC_INTR);
- }
- }
- /*
- * If the other guy failed to connect, we might as
- * well have another go.
- */
- if (!rc->rc_client || rc->rc_closed)
- goto again;
+ if (rc->rc_client) {
mtx_unlock(&rc->rc_lock);
return (RPC_SUCCESS);
- } else {
- rc->rc_connecting = TRUE;
}
+
+ /*
+ * My turn to attempt a connect. The rc_connecting variable
+ * serializes the following code sequence, so it is guaranteed
+ * that rc_client will still be NULL after it is re-locked below,
+ * since that is the only place it is set non-NULL.
+ */
+ rc->rc_connecting = TRUE;
mtx_unlock(&rc->rc_lock);
so = __rpc_nconf2socket(rc->rc_nconf);
@@ -188,43 +188,52 @@ again:
bindresvport(so, NULL);
if (rc->rc_nconf->nc_semantics == NC_TPI_CLTS)
- rc->rc_client = clnt_dg_create(so,
+ newclient = clnt_dg_create(so,
(struct sockaddr *) &rc->rc_addr, rc->rc_prog, rc->rc_vers,
rc->rc_sendsz, rc->rc_recvsz);
else
- rc->rc_client = clnt_vc_create(so,
+ newclient = clnt_vc_create(so,
(struct sockaddr *) &rc->rc_addr, rc->rc_prog, rc->rc_vers,
rc->rc_sendsz, rc->rc_recvsz);
td->td_ucred = oldcred;
- if (!rc->rc_client) {
+ if (!newclient) {
soclose(so);
rc->rc_err = rpc_createerr.cf_error;
stat = rpc_createerr.cf_stat;
goto out;
}
- CLNT_CONTROL(rc->rc_client, CLSET_FD_CLOSE, 0);
- CLNT_CONTROL(rc->rc_client, CLSET_CONNECT, &one);
- CLNT_CONTROL(rc->rc_client, CLSET_TIMEOUT, &rc->rc_timeout);
- CLNT_CONTROL(rc->rc_client, CLSET_RETRY_TIMEOUT, &rc->rc_retry);
- CLNT_CONTROL(rc->rc_client, CLSET_WAITCHAN, rc->rc_waitchan);
- CLNT_CONTROL(rc->rc_client, CLSET_INTERRUPTIBLE, &rc->rc_intr);
+ CLNT_CONTROL(newclient, CLSET_FD_CLOSE, 0);
+ CLNT_CONTROL(newclient, CLSET_CONNECT, &one);
+ CLNT_CONTROL(newclient, CLSET_TIMEOUT, &rc->rc_timeout);
+ CLNT_CONTROL(newclient, CLSET_RETRY_TIMEOUT, &rc->rc_retry);
+ CLNT_CONTROL(newclient, CLSET_WAITCHAN, rc->rc_waitchan);
+ CLNT_CONTROL(newclient, CLSET_INTERRUPTIBLE, &rc->rc_intr);
stat = RPC_SUCCESS;
out:
mtx_lock(&rc->rc_lock);
- if (rc->rc_closed) {
- if (rc->rc_client) {
- CLNT_CLOSE(rc->rc_client);
- CLNT_RELEASE(rc->rc_client);
- rc->rc_client = NULL;
- }
+ KASSERT(rc->rc_client == NULL, ("rc_client not null"));
+ if (!rc->rc_closed) {
+ rc->rc_client = newclient;
+ newclient = NULL;
}
rc->rc_connecting = FALSE;
wakeup(rc);
mtx_unlock(&rc->rc_lock);
+ if (newclient) {
+ /*
+ * It has been closed, so discard the new client.
+ * nb: clnt_[dg|vc]_close()/clnt_[dg|vc]_destroy() cannot
+ * be called with the rc_lock mutex held, since they may
+ * msleep() while holding a different mutex.
+ */
+ CLNT_CLOSE(newclient);
+ CLNT_RELEASE(newclient);
+ }
+
return (stat);
}
@@ -240,19 +249,24 @@ clnt_reconnect_call(
struct rc_data *rc = (struct rc_data *)cl->cl_private;
CLIENT *client;
enum clnt_stat stat;
- int tries;
+ int tries, error;
tries = 0;
do {
+ mtx_lock(&rc->rc_lock);
if (rc->rc_closed) {
+ mtx_unlock(&rc->rc_lock);
return (RPC_CANTSEND);
}
if (!rc->rc_client) {
+ mtx_unlock(&rc->rc_lock);
stat = clnt_reconnect_connect(cl);
if (stat == RPC_SYSTEMERROR) {
- (void) tsleep(&fake_wchan, 0,
- "rpccon", hz);
+ error = tsleep(&fake_wchan,
+ rc->rc_intr ? PCATCH : 0, "rpccon", hz);
+ if (error == EINTR || error == ERESTART)
+ return (RPC_INTR);
tries++;
if (tries >= rc->rc_retries)
return (stat);
@@ -260,9 +274,9 @@ clnt_reconnect_call(
}
if (stat != RPC_SUCCESS)
return (stat);
+ mtx_lock(&rc->rc_lock);
}
- mtx_lock(&rc->rc_lock);
if (!rc->rc_client) {
mtx_unlock(&rc->rc_lock);
stat = RPC_FAILED;
@@ -279,7 +293,6 @@ clnt_reconnect_call(
CLNT_GETERR(client, &rc->rc_err);
}
- CLNT_RELEASE(client);
if (stat == RPC_TIMEDOUT) {
/*
* Check for async send misfeature for NLM
@@ -290,6 +303,7 @@ clnt_reconnect_call(
|| (rc->rc_timeout.tv_sec == -1
&& utimeout.tv_sec == 0
&& utimeout.tv_usec == 0)) {
+ CLNT_RELEASE(client);
break;
}
}
@@ -297,8 +311,10 @@ clnt_reconnect_call(
if (stat == RPC_TIMEDOUT || stat == RPC_CANTSEND
|| stat == RPC_CANTRECV) {
tries++;
- if (tries >= rc->rc_retries)
+ if (tries >= rc->rc_retries) {
+ CLNT_RELEASE(client);
break;
+ }
if (ext && ext->rc_feedback)
ext->rc_feedback(FEEDBACK_RECONNECT, proc,
@@ -307,14 +323,22 @@ clnt_reconnect_call(
mtx_lock(&rc->rc_lock);
/*
* Make sure that someone else hasn't already
- * reconnected.
+ * reconnected by checking if rc_client has changed.
+ * If not, we are done with the client and must
+ * do CLNT_RELEASE(client) twice to dispose of it,
+ * because there is both an initial refcnt and one
+ * acquired by CLNT_ACQUIRE() above.
*/
if (rc->rc_client == client) {
- CLNT_RELEASE(rc->rc_client);
rc->rc_client = NULL;
+ mtx_unlock(&rc->rc_lock);
+ CLNT_RELEASE(client);
+ } else {
+ mtx_unlock(&rc->rc_lock);
}
- mtx_unlock(&rc->rc_lock);
+ CLNT_RELEASE(client);
} else {
+ CLNT_RELEASE(client);
break;
}
} while (stat != RPC_SUCCESS);
@@ -333,6 +357,10 @@ clnt_reconnect_geterr(CLIENT *cl, struct
*errp = rc->rc_err;
}
+/*
+ * Since this function requires that rc_client be valid, it can
+ * only be called when that is guaranteed to be the case.
+ */
static bool_t
clnt_reconnect_freeres(CLIENT *cl, xdrproc_t xdr_res, void *res_ptr)
{
@@ -347,6 +375,10 @@ clnt_reconnect_abort(CLIENT *h)
{
}
+/*
+ * CLNT_CONTROL() on the client returned by clnt_reconnect_create() must
+ * always be called before CLNT_CALL_MBUF() by a single thread only.
+ */
static bool_t
clnt_reconnect_control(CLIENT *cl, u_int request, void *info)
{
_______________________________________________
svn-src-all@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-all
To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
