From mboxrd@z Thu Jan 1 00:00:00 1970 From: "santosh.shilimkar-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org" Subject: Re: [PATCH] RDS: sync congestion map updating Date: Fri, 1 Apr 2016 21:30:54 -0700 Message-ID: <56FF4AFE.9080606@oracle.com> References: <1459328902-31968-1-git-send-email-wen.gang.wang@oracle.com> <20160330161952.GA2670@leon.nu> <56FC09D6.7090602@oracle.com> <56FC82B7.3070504@oracle.com> <56FC927E.9090404@oracle.com> <56FED04C.2060806@oracle.com> <20160402011459.GC8565@leon.nu> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20160402011459.GC8565-2ukJVAZIZ/Y@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Wengang Wang , netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org On 4/1/16 6:14 PM, Leon Romanovsky wrote: > On Fri, Apr 01, 2016 at 12:47:24PM -0700, santosh shilimkar wrote: >> (cc-ing netdev) >> On 3/30/2016 7:59 PM, Wengang Wang wrote: >>> >>> >>> =E5=9C=A8 2016=E5=B9=B403=E6=9C=8831=E6=97=A5 09:51, Wengang Wang =E5= =86=99=E9=81=93: >>>> >>>> >>>> =E5=9C=A8 2016=E5=B9=B403=E6=9C=8831=E6=97=A5 01:16, santosh shili= mkar =E5=86=99=E9=81=93: >>>>> Hi Wengang, >>>>> >>>>> On 3/30/2016 9:19 AM, Leon Romanovsky wrote: >>>>>> On Wed, Mar 30, 2016 at 05:08:22PM +0800, Wengang Wang wrote: >>>>>>> Problem is found that some among a lot of parallel RDS >>>>>>> communications hang. >>>>>>> In my test ten or so among 33 communications hang. The send >>>>>>> requests got >>>>>>> -ENOBUF error meaning the peer socket (port) is congested. But >>>>>>> meanwhile, >>>>>>> peer socket (port) is not congested. >>>>>>> >>>>>>> The congestion map updating can happen in two paths: one is in >>>>>>> rds_recvmsg path >>>>>>> and the other is when it receives packets from the hardware. Th= ere >>>>>>> is no >>>>>>> synchronization when updating the congestion map. So a bit >>>>>>> operation (clearing) >>>>>>> in the rds_recvmsg path can be skipped by another bit operation >>>>>>> (setting) in >>>>>>> hardware packet receving path. >>>>>>> >>> >>> To be more detailed. Here, the two paths (user calls recvmsg and >>> hardware receives data) are for different rds socks. thus the >>> rds_sock->rs_recv_lock is not helpful to sync the updating on conge= stion >>> map. >>> >> For archive purpose, let me try to conclude the thread. I synced >> with Wengang offlist and came up with below fix. I was under >> impression that __set_bit_le() was atmoic version. After fixing >> it like patch(end of the email), the bug gets addressed. >> >> I will probably send this as fix for stable as well. >> >> >> From 5614b61f6fdcd6ae0c04e50b97efd13201762294 Mon Sep 17 00:00:00 2= 001 >> From: Santosh Shilimkar >> Date: Wed, 30 Mar 2016 23:26:47 -0700 >> Subject: [PATCH] RDS: Fix the atomicity for congestion map update >> >> Two different threads with different rds sockets may be in >> rds_recv_rcvbuf_delta() via receive path. If their ports >> both map to the same word in the congestion map, then >> using non-atomic ops to update it could cause the map to >> be incorrect. Lets use atomics to avoid such an issue. >> >> Full credit to Wengang for >> finding the issue, analysing it and also pointing out >> to offending code with spin lock based fix. > > I'm glad that you solved the issue without spinlocks. > Out of curiosity, I see that this patch is needed to be sent > to Dave and applied by him. Is it right? > Right. I was planning send this one along with one more fix together on netdev for Dave to pick it up. > =E2=9E=9C linus-tree git:(master) ./scripts/get_maintainer.pl -f net= /rds/cong.c > Santosh Shilimkar (supporter:RDS - > RELIABLE DATAGRAM SOCKETS) > "David S. Miller" (maintainer:NETWORKING > [GENERAL]) > netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list:RDS - RELIABLE DATAGRAM SOCKETS) > linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list:RDS - RELIABLE DATAGRAM SOCKETS= ) > rds-devel-N0ozoZBvEnrZJqsBc5GL+g@public.gmane.org (moderated list:RDS - RELIABLE DATAGRAM > SOCKETS) > linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org (open list) > >> >> Signed-off-by: Wengang Wang >> Signed-off-by: Santosh Shilimkar > > Reviewed-by: Leon Romanovsky > Thanks for review. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html