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,URIBL_BLOCKED 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 CF2ECC433DB for ; Wed, 3 Feb 2021 16:01:52 +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 0888B64F65 for ; Wed, 3 Feb 2021 16:01:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0888B64F65 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]:36016 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7KbG-0000uH-9t for qemu-devel@archiver.kernel.org; Wed, 03 Feb 2021 11:01:50 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:46084) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7KZE-0008VB-SI for qemu-devel@nongnu.org; Wed, 03 Feb 2021 10:59:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:46658) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7KZB-0002kF-LN for qemu-devel@nongnu.org; Wed, 03 Feb 2021 10:59:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612367980; 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=k0Rya2RSACKXp2RWkiOTGQ4uvf+SQEdNc874ydXkCqc=; b=H2xmpsW40cMHMPfQcJUS0x+Urapk6zzbcdMy2NwUr6JdD9jaRCSoJMbAiD0egNHCFhZ81t A4AqpSy+1Z6fv0P+Wp+chDdL65A2eQvpULiPEsIzL2u0x7o9XToSMpRo+Gg4u/pH9CkuMJ 4zjKOcLEeu5xqrleEEBWWucTCdBy/kg= 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-96--9DdxRo1OCCr1aLmxnZNfw-1; Wed, 03 Feb 2021 10:59:39 -0500 X-MC-Unique: -9DdxRo1OCCr1aLmxnZNfw-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 57499801960; Wed, 3 Feb 2021 15:59:38 +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 14F445885D; Wed, 3 Feb 2021 15:59:35 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 93B9522054F; Wed, 3 Feb 2021 10:59:34 -0500 (EST) Date: Wed, 3 Feb 2021 10:59:34 -0500 From: Vivek Goyal To: Greg Kurz Subject: Re: [PATCH] virtiofsd: vu_dispatch locking should never fail Message-ID: <20210203155934.GB3307@redhat.com> References: <20210129155312.595980-1-groug@kaod.org> MIME-Version: 1.0 In-Reply-To: <20210129155312.595980-1-groug@kaod.org> 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=63.128.21.124; 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_H4=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 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. 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 >