From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit d10f27a750312ed5638c876e4bd6aa83664cccd8 upstream.
The rpc server tries to ensure that there will be room to send a reply
before it receives a request.
It does this by tracking, in xpt_reserved, an upper bound on the total
size of the replies that is has already committed to for the socket.
Currently it is adding in the estimate for a new reply *before* it
checks whether there is space available. If it finds that there is not
space, it then subtracts the estimate back out.
This may lead the subsequent svc_xprt_enqueue to decide that there is
space after all.
The results is a svc_recv() that will repeatedly return -EAGAIN, causing
server threads to loop without doing any actual work.
Reported-by: Michael Tokarev <mjt@xxxxxxxxxx>
Tested-by: Michael Tokarev <mjt@xxxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
net/sunrpc/svc_xprt.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 957a7e88e827..afa0bceb67ad 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -310,7 +310,6 @@ static void svc_thread_dequeue(struct svc_pool *pool, struct svc_rqst *rqstp)
*/
void svc_xprt_enqueue(struct svc_xprt *xprt)
{
- struct svc_serv *serv = xprt->xpt_server;
struct svc_pool *pool;
struct svc_rqst *rqstp;
int cpu;
@@ -384,8 +383,6 @@ void svc_xprt_enqueue(struct svc_xprt *xprt)
rqstp, rqstp->rq_xprt);
rqstp->rq_xprt = xprt;
svc_xprt_get(xprt);
- rqstp->rq_reserved = serv->sv_max_mesg;
- atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
pool->sp_stats.threads_woken++;
BUG_ON(xprt->xpt_pool != pool);
wake_up(&rqstp->rq_wait);
@@ -663,8 +660,6 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
if (xprt) {
rqstp->rq_xprt = xprt;
svc_xprt_get(xprt);
- rqstp->rq_reserved = serv->sv_max_mesg;
- atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
} else {
/* No data pending. Go to sleep */
svc_thread_enqueue(pool, rqstp);
@@ -754,6 +749,8 @@ int svc_recv(struct svc_rqst *rqstp, long timeout)
} else
len = xprt->xpt_ops->xpo_recvfrom(rqstp);
dprintk("svc: got len=%d\n", len);
+ rqstp->rq_reserved = serv->sv_max_mesg;
+ atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
}
/* No data, incomplete (TCP) read, or accept() */
--
1.8.5.2
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html