From nobody Wed Nov 19 00:10:50 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=pass(p=none dis=none) header.from=redhat.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1613501251218745.305286463349; Tue, 16 Feb 2021 10:47:31 -0800 (PST) Received: from localhost ([::1]:55654 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lC5Nh-00024k-QY for importer@patchew.org; Tue, 16 Feb 2021 13:47:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:36978) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lC5ER-0004Lg-5x for qemu-devel@nongnu.org; Tue, 16 Feb 2021 13:37:56 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:38595) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lC5EO-0000Ft-FD for qemu-devel@nongnu.org; Tue, 16 Feb 2021 13:37:54 -0500 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-430-67X2meu2NY2J_NedlqFjaQ-1; Tue, 16 Feb 2021 13:37:47 -0500 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 9945B107ACE4; Tue, 16 Feb 2021 18:37:46 +0000 (UTC) Received: from dgilbert-t580.localhost (ovpn-115-109.ams2.redhat.com [10.36.115.109]) by smtp.corp.redhat.com (Postfix) with ESMTP id 422D35C1B4; Tue, 16 Feb 2021 18:37:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613500671; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ePzcSXu+xFi0EtP7a7da9l5xGiaV91m8gitJFP8nLz8=; b=f//VeBAi7JjokHY2qOBz+Kr8EvWoO2xNCRDHjtO2TPmEJwdsYQa4oKUKNYkhC0+jLw/BJK nJHeVsiuoNPEmRt98i2WiWppzNHj171Izgag6d/yCZxGeXV+uRxYpv+b5N3VV4DMRWBSOf x11Amb6ItwcTV7VYQqW88dYcdB4C67s= X-MC-Unique: 67X2meu2NY2J_NedlqFjaQ-1 From: "Dr. David Alan Gilbert (git)" To: qemu-devel@nongnu.org, wainersm@redhat.com, groug@kaod.org, philmd@redhat.com, vgoyal@redhat.com Subject: [PULL 2/6] virtiofsd: vu_dispatch locking should never fail Date: Tue, 16 Feb 2021 18:37:30 +0000 Message-Id: <20210216183734.57810-3-dgilbert@redhat.com> In-Reply-To: <20210216183734.57810-1-dgilbert@redhat.com> References: <20210216183734.57810-1-dgilbert@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=63.128.21.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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: virtio-fs@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Type: text/plain; charset="utf-8" From: Greg Kurz 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 for improved consistency and robustness. This is just cleanup. It doesn't fix any actual issue. Signed-off-by: Greg Kurz Message-Id: <20210203182434.93870-1-groug@kaod.org> Reviewed-by: Vivek Goyal Reviewed-by: Stefan Hajnoczi Signed-off-by: Dr. David Alan Gilbert --- tools/virtiofsd/fuse_virtio.c | 49 +++++++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 14 deletions(-) diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c index ddcefee427..523ee64fb7 100644 --- a/tools/virtiofsd/fuse_virtio.c +++ b/tools/virtiofsd/fuse_virtio.c @@ -187,6 +187,31 @@ static void copy_iov(struct iovec *src_iov, int src_co= unt, } } =20 +/* + * 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. + */ +static void vu_dispatch_rdlock(struct fv_VuDev *vud) +{ + int ret =3D pthread_rwlock_rdlock(&vud->vu_dispatch_rwlock); + assert(ret =3D=3D 0); +} + +static void vu_dispatch_wrlock(struct fv_VuDev *vud) +{ + int ret =3D pthread_rwlock_wrlock(&vud->vu_dispatch_rwlock); + assert(ret =3D=3D 0); +} + +static void vu_dispatch_unlock(struct fv_VuDev *vud) +{ + int ret =3D pthread_rwlock_unlock(&vud->vu_dispatch_rwlock); + assert(ret =3D=3D 0); +} + /* * 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 +265,12 @@ int virtio_send_msg(struct fuse_session *se, struct f= use_chan *ch, =20 copy_iov(iov, count, in_sg, in_num, tosend_len); =20 - 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); =20 req->reply_sent =3D true; =20 @@ -403,12 +428,12 @@ int virtio_send_data_iov(struct fuse_session *se, str= uct fuse_chan *ch, =20 ret =3D 0; =20 - 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); =20 err: if (ret =3D=3D 0) { @@ -558,12 +583,12 @@ out: fuse_log(FUSE_LOG_DEBUG, "%s: elem %d no reply sent\n", __func__, elem->index); =20 - 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); } =20 pthread_mutex_destroy(&req->ch.lock); @@ -596,7 +621,6 @@ static void *fv_queue_thread(void *opaque) qi->qidx, qi->kick_fd); while (1) { struct pollfd pf[2]; - int ret; =20 pf[0].fd =3D qi->kick_fd; pf[0].events =3D POLLIN; @@ -645,8 +669,7 @@ static void *fv_queue_thread(void *opaque) break; } /* Mutual exclusion with virtio_loop() */ - ret =3D pthread_rwlock_rdlock(&qi->virtio_dev->vu_dispatch_rwlock); - assert(ret =3D=3D 0); /* there is no possible error case */ + vu_dispatch_rdlock(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 +695,7 @@ static void *fv_queue_thread(void *opaque) } =20 pthread_mutex_unlock(&qi->vq_lock); - pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock); + vu_dispatch_unlock(qi->virtio_dev); =20 /* Process all the requests. */ if (!se->thread_pool_size && req_list !=3D NULL) { @@ -799,7 +822,6 @@ int virtio_loop(struct fuse_session *se) while (!fuse_session_exited(se)) { struct pollfd pf[1]; bool ok; - int ret; pf[0].fd =3D se->vu_socketfd; pf[0].events =3D POLLIN; pf[0].revents =3D 0; @@ -825,12 +847,11 @@ 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 =3D pthread_rwlock_wrlock(&se->virtio_dev->vu_dispatch_rwlock); - assert(ret =3D=3D 0); /* there is no possible error case */ + vu_dispatch_wrlock(se->virtio_dev); =20 ok =3D vu_dispatch(&se->virtio_dev->dev); =20 - pthread_rwlock_unlock(&se->virtio_dev->vu_dispatch_rwlock); + vu_dispatch_unlock(se->virtio_dev); =20 if (!ok) { fuse_log(FUSE_LOG_ERR, "%s: vu_dispatch failed\n", __func__); --=20 2.29.2