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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 8F508C433DB for ; Wed, 3 Feb 2021 16:41:16 +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 B89FE64E4B for ; Wed, 3 Feb 2021 16:41:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B89FE64E4B 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]:38198 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7LDO-0008KW-K7 for qemu-devel@archiver.kernel.org; Wed, 03 Feb 2021 11:41:14 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54070) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7L1x-0004tj-Fj for qemu-devel@nongnu.org; Wed, 03 Feb 2021 11:29:25 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:55480) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7L1v-0003RT-Fj for qemu-devel@nongnu.org; Wed, 03 Feb 2021 11:29:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612369762; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gZvaZGyMsAdRlQYagAIbZ4mbbCF0fkX5zslSmVG60hU=; b=EPVBdUYJBRZEZs1k4UIFA9lOvgSBKIHOIxjzgFtUvD1ZOu1YUgxvCJlOVP2cUaM4GRlt+y mwvDt/dVXDrJYorvSa1aNuvakmBGwp1NRB8nAz8VNwFMAg8CWeTEilEmhLTt1s4lmvnrnW bJNJcHBvbS3dVfxNgQa6MNAxBeeUnXM= 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-477-7kAQ09EQP-SNhkpIExQ-mQ-1; Wed, 03 Feb 2021 11:29:21 -0500 X-MC-Unique: 7kAQ09EQP-SNhkpIExQ-mQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 31F17107ACE3; Wed, 3 Feb 2021 16:29:20 +0000 (UTC) Received: from horse.redhat.com (ovpn-116-88.rdu2.redhat.com [10.10.116.88]) by smtp.corp.redhat.com (Postfix) with ESMTP id E74125885D; Wed, 3 Feb 2021 16:29:15 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 7F62222054F; Wed, 3 Feb 2021 11:29:15 -0500 (EST) Date: Wed, 3 Feb 2021 11:29:15 -0500 From: Vivek Goyal To: Greg Kurz Subject: Re: [PATCH] virtiofsd: vu_dispatch locking should never fail Message-ID: <20210203162915.GD3307@redhat.com> References: <20210129155312.595980-1-groug@kaod.org> <20210203155934.GB3307@redhat.com> <20210203170857.626224b0@bahia.lan> MIME-Version: 1.0 In-Reply-To: <20210203170857.626224b0@bahia.lan> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vgoyal@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=vgoyal@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.539, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: qemu-devel@nongnu.org, Stefan Hajnoczi , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Feb 03, 2021 at 05:08:57PM +0100, Greg Kurz wrote: > On Wed, 3 Feb 2021 10:59:34 -0500 > Vivek Goyal wrote: > > > On Fri, Jan 29, 2021 at 04:53:12PM +0100, Greg Kurz wrote: > > > pthread_rwlock_rdlock() and pthread_rwlock_wrlock() can fail if a > > > deadlock condition is detected or the current thread already owns > > > the lock. They can also fail, like pthread_rwlock_unlock(), if the > > > mutex wasn't properly initialized. None of these are ever expected > > > to happen with fv_VuDev::vu_dispatch_rwlock. > > > > > > Some users already check the return value and assert, some others > > > don't. Introduce rdlock/wrlock/unlock wrappers that just do the > > > former and use them everywhere. > > > > > > Signed-off-by: Greg Kurz > > > --- > > > tools/virtiofsd/fuse_virtio.c | 42 +++++++++++++++++++++++------------ > > > 1 file changed, 28 insertions(+), 14 deletions(-) > > > > > > diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c > > > index ddcefee4272f..7ea269c4b65d 100644 > > > --- a/tools/virtiofsd/fuse_virtio.c > > > +++ b/tools/virtiofsd/fuse_virtio.c > > > @@ -187,6 +187,24 @@ static void copy_iov(struct iovec *src_iov, int src_count, > > > } > > > } > > > > > > +/* > > > + * pthread_rwlock_rdlock() and pthread_rwlock_wrlock can fail if > > > + * a deadlock condition is detected or the current thread already > > > + * owns the lock. They can also fail, like pthread_rwlock_unlock(), > > > + * if the mutex wasn't properly initialized. None of these are ever > > > + * expected to happen. > > > + */ > > > +#define VU_DISPATCH_LOCK_OP(op) \ > > > +static inline void vu_dispatch_##op(struct fv_VuDev *vud) \ > > > +{ \ > > > + int ret = pthread_rwlock_##op(&vud->vu_dispatch_rwlock); \ > > > + assert(ret == 0); \ > > > +} > > > + > > > +VU_DISPATCH_LOCK_OP(rdlock); > > > +VU_DISPATCH_LOCK_OP(wrlock); > > > +VU_DISPATCH_LOCK_OP(unlock); > > > + > > > > I generally do not prefer using macros to define functions as searching > > to functions declarations/definitions becomes harder. But I see lot > > of people prefer that because they can reduce number of lines of code. > > > > Well, I must admit I hesitated since this doesn't gain much in > terms of LoC compared to the expanded version. I'm perfectly > fine with dropping the macro in my v2 if this looks better > to you. If you are posting V2 anyway, so lets do it. Agreed, we are not saving many lines where so why to use macros to define functions. Vivek > > > Apart from that one issue of using rdlock in fv_queue_thread(), stefan > > pointed, it looks good to me. > > > > Reviewed-by: Vivek Goyal > > > > Vivek > > > /* > > > * Called back by ll whenever it wants to send a reply/message back > > > * The 1st element of the iov starts with the fuse_out_header > > > @@ -240,12 +258,12 @@ int virtio_send_msg(struct fuse_session *se, struct fuse_chan *ch, > > > > > > copy_iov(iov, count, in_sg, in_num, tosend_len); > > > > > > - pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_rdlock(qi->virtio_dev); > > > pthread_mutex_lock(&qi->vq_lock); > > > vu_queue_push(dev, q, elem, tosend_len); > > > vu_queue_notify(dev, q); > > > pthread_mutex_unlock(&qi->vq_lock); > > > - pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_unlock(qi->virtio_dev); > > > > > > req->reply_sent = true; > > > > > > @@ -403,12 +421,12 @@ int virtio_send_data_iov(struct fuse_session *se, struct fuse_chan *ch, > > > > > > ret = 0; > > > > > > - pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_rdlock(qi->virtio_dev); > > > pthread_mutex_lock(&qi->vq_lock); > > > vu_queue_push(dev, q, elem, tosend_len); > > > vu_queue_notify(dev, q); > > > pthread_mutex_unlock(&qi->vq_lock); > > > - pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_unlock(qi->virtio_dev); > > > > > > err: > > > if (ret == 0) { > > > @@ -558,12 +576,12 @@ out: > > > fuse_log(FUSE_LOG_DEBUG, "%s: elem %d no reply sent\n", __func__, > > > elem->index); > > > > > > - pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_rdlock(qi->virtio_dev); > > > pthread_mutex_lock(&qi->vq_lock); > > > vu_queue_push(dev, q, elem, 0); > > > vu_queue_notify(dev, q); > > > pthread_mutex_unlock(&qi->vq_lock); > > > - pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_unlock(qi->virtio_dev); > > > } > > > > > > pthread_mutex_destroy(&req->ch.lock); > > > @@ -596,7 +614,6 @@ static void *fv_queue_thread(void *opaque) > > > qi->qidx, qi->kick_fd); > > > while (1) { > > > struct pollfd pf[2]; > > > - int ret; > > > > > > pf[0].fd = qi->kick_fd; > > > pf[0].events = POLLIN; > > > @@ -645,8 +662,7 @@ static void *fv_queue_thread(void *opaque) > > > break; > > > } > > > /* Mutual exclusion with virtio_loop() */ > > > - ret = pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > - assert(ret == 0); /* there is no possible error case */ > > > + vu_dispatch_wrlock(qi->virtio_dev); > > > pthread_mutex_lock(&qi->vq_lock); > > > /* out is from guest, in is too guest */ > > > unsigned int in_bytes, out_bytes; > > > @@ -672,7 +688,7 @@ static void *fv_queue_thread(void *opaque) > > > } > > > > > > pthread_mutex_unlock(&qi->vq_lock); > > > - pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_unlock(qi->virtio_dev); > > > > > > /* Process all the requests. */ > > > if (!se->thread_pool_size && req_list != NULL) { > > > @@ -799,7 +815,6 @@ int virtio_loop(struct fuse_session *se) > > > while (!fuse_session_exited(se)) { > > > struct pollfd pf[1]; > > > bool ok; > > > - int ret; > > > pf[0].fd = se->vu_socketfd; > > > pf[0].events = POLLIN; > > > pf[0].revents = 0; > > > @@ -825,12 +840,11 @@ int virtio_loop(struct fuse_session *se) > > > assert(pf[0].revents & POLLIN); > > > fuse_log(FUSE_LOG_DEBUG, "%s: Got VU event\n", __func__); > > > /* Mutual exclusion with fv_queue_thread() */ > > > - ret = pthread_rwlock_wrlock(&se->virtio_dev->vu_dispatch_rwlock); > > > - assert(ret == 0); /* there is no possible error case */ > > > + vu_dispatch_wrlock(se->virtio_dev); > > > > > > ok = vu_dispatch(&se->virtio_dev->dev); > > > > > > - pthread_rwlock_unlock(&se->virtio_dev->vu_dispatch_rwlock); > > > + vu_dispatch_unlock(se->virtio_dev); > > > > > > if (!ok) { > > > fuse_log(FUSE_LOG_ERR, "%s: vu_dispatch failed\n", __func__); > > > -- > > > 2.26.2 > > > > > >