From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95B78C433F5 for ; Thu, 16 Sep 2021 04:23:08 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 30B5A61178 for ; Thu, 16 Sep 2021 04:23:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 30B5A61178 Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631766187; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=CPHedjWZom4fVH/AvWx3/kzNgpHmSky15EA7QQ/pQ3w=; b=ZZyd7EM3j6jMuhhsqGeSosPeuIgQ3/Yd3jpowcJo23a6vOgTHcco7xD2D9SNNOYHJ/4ewd XwxT5La63uq+sNuNxj9MyG1NeuQv1Ltwdesl9828k8bRL8Wx8L5lE4ow8vhZDXoFvuyBGc lPO/fa9Yy8j9ga4l79ykJwb2/4borP8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-100-VMxz3DWKO965I6a_4ARntQ-1; Thu, 16 Sep 2021 00:23:05 -0400 X-MC-Unique: VMxz3DWKO965I6a_4ARntQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 67207801B3D; Thu, 16 Sep 2021 04:23:01 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 45D2E60C9F; Thu, 16 Sep 2021 04:23:01 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id 1A60E4EA29; Thu, 16 Sep 2021 04:23:01 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 18G4MxOV004853 for ; Thu, 16 Sep 2021 00:22:59 -0400 Received: by smtp.corp.redhat.com (Postfix) id D7F1E5D9D3; Thu, 16 Sep 2021 04:22:59 +0000 (UTC) Received: from octiron.msp.redhat.com (unknown [10.15.80.209]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 87FC75D9CA; Thu, 16 Sep 2021 04:22:55 +0000 (UTC) Received: from octiron.msp.redhat.com (localhost.localdomain [127.0.0.1]) by octiron.msp.redhat.com (8.14.9/8.14.9) with ESMTP id 18G4MrUV007918; Wed, 15 Sep 2021 23:22:54 -0500 Received: (from bmarzins@localhost) by octiron.msp.redhat.com (8.14.9/8.14.9/Submit) id 18G4MrYl007917; Wed, 15 Sep 2021 23:22:53 -0500 Date: Wed, 15 Sep 2021 23:22:53 -0500 From: Benjamin Marzinski To: mwilck@suse.com Message-ID: <20210916042253.GS3087@octiron.msp.redhat.com> References: <20210910114120.13665-1-mwilck@suse.com> <20210910114120.13665-34-mwilck@suse.com> MIME-Version: 1.0 In-Reply-To: <20210910114120.13665-34-mwilck@suse.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-loop: dm-devel@redhat.com Cc: lixiaokeng@huawei.com, dm-devel@redhat.com, Chongyun Wu Subject: Re: [dm-devel] [PATCH 33/35] multipathd: uxlsnr: use poll loop for sending, too X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Fri, Sep 10, 2021 at 01:41:18PM +0200, mwilck@suse.com wrote: > From: Martin Wilck > > send_packet() may busy-loop. By polling for POLLOUT, we can > avoid that, even if it's very unlikely in practice. > > Signed-off-by: Martin Wilck > --- > multipathd/uxlsnr.c | 39 ++++++++++++++++++++++++++++++++------- > 1 file changed, 32 insertions(+), 7 deletions(-) > > diff --git a/multipathd/uxlsnr.c b/multipathd/uxlsnr.c > index 1bf4126..c18b2c4 100644 > --- a/multipathd/uxlsnr.c > +++ b/multipathd/uxlsnr.c > @@ -588,15 +588,37 @@ static void handle_client(struct client *c, struct vectors *vecs, short revents) > if (get_strbuf_len(&c->reply) == 0) > default_reply(c, c->error); > > - const char *buf = get_strbuf_str(&c->reply); > + if (c->cmd_len == 0) { > + size_t len = get_strbuf_len(&c->reply) + 1; > > - if (send_packet(c->fd, buf) != 0) > - dead_client(c); > - else > - condlog(4, "cli[%d]: Reply [%zu bytes]", c->fd, > - get_strbuf_len(&c->reply) + 1); > - reset_strbuf(&c->reply); > + if (send(c->fd, &len, sizeof(len), MSG_NOSIGNAL) > + != sizeof(len)) { This assumes that failing to send the size is always an error. What about if we get EINTR/EAGAIN? Also, it seems pretty likely that we will either send all of the size or none of it, but I'm not sure we can guarantee that. send_packet() handled partitial writes of the length. Actually, mpath_recv_reply_len() which is still used by CLT_RECV still uses read_all(), instead of just polling again on partial reads. Also, the fd is not set to be non-blocking. and if we fall through to CLT_SEND, we haven't checked for a POLLOUT revent, so technically, I believe the write could block here. -Ben > + c->error = -ECONNRESET; > + return; > + } > + c->cmd_len = len; > + return; > + } > > + if (c->len < c->cmd_len) { > + const char *buf = get_strbuf_str(&c->reply); > + > + n = send(c->fd, buf + c->len, c->cmd_len, MSG_NOSIGNAL); > + if (n == -1) { > + if (errno == EAGAIN || errno == EINTR) > + return; > + else { > + c->error = -ECONNRESET; > + return; > + } > + } > + c->len += n; > + } > + if (c->len < c->cmd_len) > + /* continue polling */ > + return; > + > + condlog(4, "cli[%d]: Reply [%zu bytes]", c->fd, c->cmd_len); > set_client_state(c, CLT_RECV); > break; > > @@ -701,6 +723,9 @@ void *uxsock_listen(long ux_sock, void *trigger_data) > case CLT_RECV: > polls[i].events = POLLIN; > break; > + case CLT_SEND: > + polls[i].events = POLLOUT; > + break; > default: > /* don't poll for this client */ > continue; > -- > 2.33.0 -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel