Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:48047 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754026AbaLAWoJ (ORCPT ); Mon, 1 Dec 2014 17:44:09 -0500 Date: Mon, 1 Dec 2014 17:44:07 -0500 From: "J. Bruce Fields" To: Jeff Layton Cc: Chris Worley , linux-nfs@vger.kernel.org Subject: Re: [PATCH 1/4] sunrpc: add a rcu_head to svc_rqst and use kfree_rcu to free it Message-ID: <20141201224407.GD30749@fieldses.org> References: <1416597571-4265-1-git-send-email-jlayton@primarydata.com> <1416597571-4265-2-git-send-email-jlayton@primarydata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1416597571-4265-2-git-send-email-jlayton@primarydata.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Nov 21, 2014 at 02:19:28PM -0500, Jeff Layton wrote: > ...also make the manipulation of sp_all_threads list use RCU-friendly > functions. > > Signed-off-by: Jeff Layton > Tested-by: Chris Worley > --- > include/linux/sunrpc/svc.h | 2 ++ > include/trace/events/sunrpc.h | 3 ++- > net/sunrpc/svc.c | 10 ++++++---- > 3 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h > index 5f0ab39bf7c3..7f80a99c59e4 100644 > --- a/include/linux/sunrpc/svc.h > +++ b/include/linux/sunrpc/svc.h > @@ -223,6 +223,7 @@ static inline void svc_putu32(struct kvec *iov, __be32 val) > struct svc_rqst { > struct list_head rq_list; /* idle list */ > struct list_head rq_all; /* all threads list */ > + struct rcu_head rq_rcu_head; /* for RCU deferred kfree */ > struct svc_xprt * rq_xprt; /* transport ptr */ > > struct sockaddr_storage rq_addr; /* peer address */ > @@ -262,6 +263,7 @@ struct svc_rqst { > #define RQ_SPLICE_OK (4) /* turned off in gss privacy > * to prevent encrypting page > * cache pages */ > +#define RQ_VICTIM (5) /* about to be shut down */ > unsigned long rq_flags; /* flags field */ > > void * rq_argp; /* decoded arguments */ > diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h > index 5848fc235869..08a5fed50f34 100644 > --- a/include/trace/events/sunrpc.h > +++ b/include/trace/events/sunrpc.h > @@ -418,7 +418,8 @@ TRACE_EVENT(xs_tcp_data_recv, > { (1UL << RQ_LOCAL), "RQ_LOCAL"}, \ > { (1UL << RQ_USEDEFERRAL), "RQ_USEDEFERRAL"}, \ > { (1UL << RQ_DROPME), "RQ_DROPME"}, \ > - { (1UL << RQ_SPLICE_OK), "RQ_SPLICE_OK"}) > + { (1UL << RQ_SPLICE_OK), "RQ_SPLICE_OK"}, \ > + { (1UL << RQ_VICTIM), "RQ_VICTIM"}) > > TRACE_EVENT(svc_recv, > TP_PROTO(struct svc_rqst *rqst, int status), > diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c > index 5d9a443d21f6..4edef32f3b9f 100644 > --- a/net/sunrpc/svc.c > +++ b/net/sunrpc/svc.c > @@ -616,7 +616,7 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node) > serv->sv_nrthreads++; > spin_lock_bh(&pool->sp_lock); > pool->sp_nrthreads++; > - list_add(&rqstp->rq_all, &pool->sp_all_threads); > + list_add_rcu(&rqstp->rq_all, &pool->sp_all_threads); > spin_unlock_bh(&pool->sp_lock); > rqstp->rq_server = serv; > rqstp->rq_pool = pool; > @@ -684,7 +684,8 @@ found_pool: > * so we don't try to kill it again. > */ > rqstp = list_entry(pool->sp_all_threads.next, struct svc_rqst, rq_all); > - list_del_init(&rqstp->rq_all); > + set_bit(RQ_VICTIM, &rqstp->rq_flags); > + list_del_rcu(&rqstp->rq_all); > task = rqstp->rq_task; > } > spin_unlock_bh(&pool->sp_lock); > @@ -782,10 +783,11 @@ svc_exit_thread(struct svc_rqst *rqstp) > > spin_lock_bh(&pool->sp_lock); > pool->sp_nrthreads--; > - list_del(&rqstp->rq_all); > + if (!test_and_set_bit(RQ_VICTIM, &rqstp->rq_flags)) > + list_del_rcu(&rqstp->rq_all); Both users of RQ_VICTIM are under the sp_lock, so we don't really need an atomic test_and_set_bit, do we? But I guess svc_exit_thread probably still needs to check for the case where it's called on a thread that svc_set_num_threads has already chosen, and this works even if it's overkill. OK, fine. --b. > spin_unlock_bh(&pool->sp_lock); > > - kfree(rqstp); > + kfree_rcu(rqstp, rq_rcu_head); > > /* Release the server */ > if (serv) > -- > 2.1.0 >