Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755549AbaBEUPc (ORCPT ); Wed, 5 Feb 2014 15:15:32 -0500 Received: from mail.windriver.com ([147.11.1.11]:55586 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755317AbaBEUH7 (ORCPT ); Wed, 5 Feb 2014 15:07:59 -0500 From: Paul Gortmaker To: , CC: "J. Bruce Fields" , Paul Gortmaker Subject: [v2.6.34-stable 196/213] svcrpc: fix svc_xprt_enqueue/svc_recv busy-looping Date: Wed, 5 Feb 2014 15:02:31 -0500 Message-ID: <1391630568-49251-197-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.8.5.2 In-Reply-To: <1391630568-49251-1-git-send-email-paul.gortmaker@windriver.com> References: <1391630568-49251-1-git-send-email-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "J. Bruce Fields" ------------------- 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 Tested-by: Michael Tokarev Signed-off-by: J. Bruce Fields Signed-off-by: Paul Gortmaker --- 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 linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/