From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:54074) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fBzGT-0007hb-43 for qemu-devel@nongnu.org; Fri, 27 Apr 2018 05:02:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fBzGP-00017N-DT for qemu-devel@nongnu.org; Fri, 27 Apr 2018 05:02:01 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38000 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fBzGP-00016l-85 for qemu-devel@nongnu.org; Fri, 27 Apr 2018 05:01:57 -0400 Date: Fri, 27 Apr 2018 10:01:52 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20180427090152.GB32172@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <1524666934-8064-1-git-send-email-lidongchen@tencent.com> <1524666934-8064-4-git-send-email-lidongchen@tencent.com> <20180426164011.GM2631@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180426164011.GM2631@work-vm> Subject: Re: [Qemu-devel] [PATCH v2 3/5] migration: remove unnecessary variables len in QIOChannelRDMA List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Lidong Chen , quintela@redhat.com, qemu-devel@nongnu.org, galsha@mellanox.com, aviadye@mellanox.com, licq@mellanox.com, adido@mellanox.com, Lidong Chen On Thu, Apr 26, 2018 at 05:40:11PM +0100, Dr. David Alan Gilbert wrote: > * Lidong Chen (jemmy858585@gmail.com) wrote: > > Because qio_channel_rdma_writev and qio_channel_rdma_readv maybe invoked > > by different threads concurrently, this patch removes unnecessary variables > > len in QIOChannelRDMA and use local variable instead. > > > > Signed-off-by: Lidong Chen > > I'm OK with this patch as is; but now you're making me worried that I > don't quite understand what thrads are accessing it at the same time; we > need to document/comment what's accessed concurrently. FWIW, I have always intended that QIOChannel impls be able to support bidirectional I/O from multiple threads, provided they each are using it in a different direction. So this is a mistake in my original RDMA impl. > > Reviewed-by: Dr. David Alan Gilbert > > > --- > > migration/rdma.c | 15 +++++++-------- > > 1 file changed, 7 insertions(+), 8 deletions(-) > > > > diff --git a/migration/rdma.c b/migration/rdma.c > > index c745427..f5c1d02 100644 > > --- a/migration/rdma.c > > +++ b/migration/rdma.c > > @@ -404,7 +404,6 @@ struct QIOChannelRDMA { > > QIOChannel parent; > > RDMAContext *rdma; > > QEMUFile *file; > > - size_t len; > > bool blocking; /* XXX we don't actually honour this yet */ > > }; > > > > @@ -2640,6 +2639,7 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc, > > int ret; > > ssize_t done = 0; > > size_t i; > > + size_t len = 0; > > > > CHECK_ERROR_STATE(); > > > > @@ -2659,10 +2659,10 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc, > > while (remaining) { > > RDMAControlHeader head; > > > > - rioc->len = MIN(remaining, RDMA_SEND_INCREMENT); > > - remaining -= rioc->len; > > + len = MIN(remaining, RDMA_SEND_INCREMENT); > > + remaining -= len; > > > > - head.len = rioc->len; > > + head.len = len; > > head.type = RDMA_CONTROL_QEMU_FILE; > > > > ret = qemu_rdma_exchange_send(rdma, &head, data, NULL, NULL, NULL); > > @@ -2672,8 +2672,8 @@ static ssize_t qio_channel_rdma_writev(QIOChannel *ioc, > > return ret; > > } > > > > - data += rioc->len; > > - done += rioc->len; > > + data += len; > > + done += len; > > } > > } > > > > @@ -2768,8 +2768,7 @@ static ssize_t qio_channel_rdma_readv(QIOChannel *ioc, > > } > > } > > } > > - rioc->len = done; > > - return rioc->len; > > + return done; > > } > > > > /* > > -- > > 1.8.3.1 > > > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|