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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 2A646C49ED9 for ; Tue, 10 Sep 2019 16:15:28 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 F153C2082C for ; Tue, 10 Sep 2019 16:15:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F153C2082C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:42036 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7ine-0005B1-Op for qemu-devel@archiver.kernel.org; Tue, 10 Sep 2019 12:15:26 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:42512) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i7ikH-0001dx-Rm for qemu-devel@nongnu.org; Tue, 10 Sep 2019 12:11:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i7ikG-00046T-Qu for qemu-devel@nongnu.org; Tue, 10 Sep 2019 12:11:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53730) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i7ikE-000436-CJ; Tue, 10 Sep 2019 12:11:54 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AB618300DA2C; Tue, 10 Sep 2019 16:11:53 +0000 (UTC) Received: from dhcp-4-67.tlv.redhat.com (dhcp-4-67.tlv.redhat.com [10.35.4.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3A81C1001948; Tue, 10 Sep 2019 16:11:52 +0000 (UTC) Message-ID: <781db018f83aa375b9a7476028c7ef8c4c24d848.camel@redhat.com> From: Maxim Levitsky To: Max Reitz , qemu-block@nongnu.org Date: Tue, 10 Sep 2019 19:11:51 +0300 In-Reply-To: <20190910124136.10565-4-mreitz@redhat.com> References: <20190910124136.10565-1-mreitz@redhat.com> <20190910124136.10565-4-mreitz@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Tue, 10 Sep 2019 16:11:53 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v2 3/7] curl: Check completion in curl_multi_do() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , qemu-stable@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 2019-09-10 at 14:41 +0200, Max Reitz wrote: > While it is more likely that transfers complete after some file > descriptor has data ready to read, we probably should not rely on it. > Better be safe than sorry and call curl_multi_check_completion() in > curl_multi_do(), too, just like it is done in curl_multi_read(). > > With this change, curl_multi_do() and curl_multi_read() are actually the > same, so drop curl_multi_read() and use curl_multi_do() as the sole FD > handler. I understand the reasoning, but I still a bit worry that this could paper over some bug/race in the future. If curl asks us only to deal with write, that would mean that it doesn't expect any data to be received. Do you by a chance have an example, of this patch affecting the code? Maybe when a unexpected error reply is received from the server? I don't really know the CURL library, so I probably missed something important. Other than that, Reviewed-by: Maxim Levitsky Best regards, Maxim Levitsky > > Signed-off-by: Max Reitz > --- > block/curl.c | 14 ++------------ > 1 file changed, 2 insertions(+), 12 deletions(-) > > diff --git a/block/curl.c b/block/curl.c > index 95d7b77dc0..5838afef99 100644 > --- a/block/curl.c > +++ b/block/curl.c > @@ -139,7 +139,6 @@ typedef struct BDRVCURLState { > > static void curl_clean_state(CURLState *s); > static void curl_multi_do(void *arg); > -static void curl_multi_read(void *arg); > > #ifdef NEED_CURL_TIMER_CALLBACK > /* Called from curl_multi_do_locked, with s->mutex held. */ > @@ -186,7 +185,7 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action, > switch (action) { > case CURL_POLL_IN: > aio_set_fd_handler(s->aio_context, fd, false, > - curl_multi_read, NULL, NULL, state); > + curl_multi_do, NULL, NULL, state); > break; > case CURL_POLL_OUT: > aio_set_fd_handler(s->aio_context, fd, false, > @@ -194,7 +193,7 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action, > break; > case CURL_POLL_INOUT: > aio_set_fd_handler(s->aio_context, fd, false, > - curl_multi_read, curl_multi_do, NULL, state); > + curl_multi_do, curl_multi_do, NULL, state); > break; > case CURL_POLL_REMOVE: > aio_set_fd_handler(s->aio_context, fd, false, > @@ -416,15 +415,6 @@ static void curl_multi_do(void *arg) > { > CURLState *s = (CURLState *)arg; > > - qemu_mutex_lock(&s->s->mutex); > - curl_multi_do_locked(s); > - qemu_mutex_unlock(&s->s->mutex); > -} > - > -static void curl_multi_read(void *arg) > -{ > - CURLState *s = (CURLState *)arg; > - > qemu_mutex_lock(&s->s->mutex); > curl_multi_do_locked(s); > curl_multi_check_completion(s->s);