diff options
| author | J. Bruce Fields <bfields@redhat.com> | 2012-08-17 17:31:53 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-09-14 10:00:19 -0700 |
| commit | 973caa9ec69452d87f65e67019429be5265f2534 (patch) | |
| tree | c2fd5a6e895d37f93e9dad62c773481ca251d366 | |
| parent | 389aec33837aeaf7e7e3cb31b6f1c6da6b009fb6 (diff) | |
| download | lwn-973caa9ec69452d87f65e67019429be5265f2534.tar.gz lwn-973caa9ec69452d87f65e67019429be5265f2534.zip | |
svcrpc: fix svc_xprt_enqueue/svc_recv busy-looping
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@tls.msk.ru>
Tested-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | net/sunrpc/svc_xprt.c | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 4bda09d7e1a4..9c9131bef48d 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -316,7 +316,6 @@ static bool svc_xprt_has_something_to_do(struct svc_xprt *xprt) */ 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; @@ -362,8 +361,6 @@ 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++; wake_up(&rqstp->rq_wait); } else { @@ -643,8 +640,6 @@ 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); /* As there is a shortage of threads and this request * had to be queued, don't allow the thread to wait so @@ -741,6 +736,8 @@ 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); } svc_xprt_received(xprt); |