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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id EC785CD4F3D for ; Thu, 21 May 2026 19:02:58 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 3154710E53B; Thu, 21 May 2026 19:02:58 +0000 (UTC) Received: from mail-ot1-f72.google.com (mail-ot1-f72.google.com [209.85.210.72]) by gabe.freedesktop.org (Postfix) with ESMTPS id CD08910E53B for ; Thu, 21 May 2026 19:02:56 +0000 (UTC) Received: by mail-ot1-f72.google.com with SMTP id 46e09a7af769-7e56806cfecso7986146a34.0 for ; Thu, 21 May 2026 12:02:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779390176; x=1779994976; h=content-transfer-encoding:cc:to:from:subject:message-id:in-reply-to :date:mime-version:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=0krv0nUw1/ioDEFf9ZMQESopIiNp/OLFryuhF9m9kKI=; b=Yzxh4TF9PEB6sweMKUVQCVVS54++tOaWkw5/1fwrLRY1GWmYqbTYFtdPh8apVB/HcX DmmlPCySgnLSR8GwLdVR9JhqjDHIUbQrXSExBv1B6bIDbfWVQpdTS5mfP/5QDCjXXc2v EDJUv+QZCQPlJNAdSUMu3qKKqUNEttFipt4M9RUHXVO/NlkcmvQCn+GU6qD5ycR356Uk b4FT0dRH6mE7qGP77peBtPkoDu8sUw3Y3MKpCejMglX2Aw3vBHR1C7mRg9rnRdvF9XdB KQHN8uga6KrFyXW0C/f/t5eKqGY6BSMH0wlYt84BI/az9SZHwcnLsi1ViNgJsNo+rwln a8ZQ== X-Forwarded-Encrypted: i=1; AFNElJ95qeHjG990Dl9DA1WGzw8Fc40tla9lpCsi1CmCR5FAIHNJdyOl9R9yYajc7suHIuQUYwXonVQSogY=@lists.freedesktop.org X-Gm-Message-State: AOJu0YxXBVz+3IHiDB5DJg++DygkJfFQUGLJIa3gb6sRRZunNxfKGqVJ rRFoj9pX6gCFIN78s0s25PCcVUehCOl/EVMCVR9nELRjeWT3WQ468QNdST69dwJmQY9j5XGUXNa CC8l+xWn3jtvk/7XzpdBejjQUVYy1mad5LdIISOZcjUkt4r9Di0BTW6Vil1w= MIME-Version: 1.0 X-Received: by 2002:a05:6830:6d0c:b0:7dc:d99c:c441 with SMTP id 46e09a7af769-7e5fedc8241mr302592a34.8.1779390176127; Thu, 21 May 2026 12:02:56 -0700 (PDT) Date: Thu, 21 May 2026 12:02:56 -0700 In-Reply-To: <4bc3709f-21bc-49f5-8fcf-972dec1397f7@collabora.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a0f56e0.050a0220.3a257.0000.GAE@google.com> Subject: Re: [PATCH v2] drm/virtio: abort virtqueue wait on device removal to avoid hung task From: syzbot To: dmitry.osipenko@collabora.com Cc: airlied@redhat.com, dmitry.osipenko@collabora.com, dri-devel@lists.freedesktop.org, gurchetansingh@chromium.org, kraxel@redhat.com, linux-kernel@vger.kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, olvaffe@gmail.com, ryasuoka@redhat.com, simona@ffwll.ch, tzimmermann@suse.de, virtualization@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" > 21.05.2026 05:19, Ryosuke Yasuoka =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> virtio_gpu_queue_ctrl_sgs() and virtio_gpu_queue_cursor() use >> wait_event() without any abort condition when waiting for virtqueue >> space. If the host device stops processing commands, these waits block >> indefinitely inside a drm_dev_enter/exit() critical section. Since >> drm_dev_unplug(), which is called in device removal and system shutdown >> call path, blocks on synchronize_srcu() until all critical sections >> complete, device removal and system shutdown also hang. >>=20 >> Add a vqs_released flag to virtio_gpu_device and include it in the >> wait_event() condition. Set the flag and wake up both queues in a new >> virtio_gpu_release_vqs() helper, called before drm_dev_unplug() in both >> virtio_gpu_remove() and virtio_gpu_shutdown(). When the flag is set, the >> wait returns immediately and the command is aborted, following the same >> cleanup path as drm_dev_enter() failure. >>=20 >> Reported-by: syzbot+d6dd6f86d3aaf7eebe7406e45c1c6e549453f224@syzkaller.a= ppspotmail.com >> Closes: https://syzkaller.appspot.com/bug?id=3Dd6dd6f86d3aaf7eebe7406e45= c1c6e549453f224 >> Reported-by: syzbot+908bd910da5dd79b88de4cf7baf376cc873a922e@syzkaller.a= ppspotmail.com >> Closes: https://syzkaller.appspot.com/bug?id=3D908bd910da5dd79b88de4cf7b= af376cc873a922e >> Signed-off-by: Ryosuke Yasuoka >> --- >> Changes in v2: >> - Update the commit message. >> - Replace wait_event_timeout() with wait_event() using a compound >> condition that includes a new vqs_released flag. >> - Add virtio_gpu_release_vqs() helper to set the flag and wake up >> both queues, called before drm_dev_unplug() in remove and shutdown >> paths. >> - Remove the hardcoded 5-second timeout. Recovery is now driven by >> the driver flag instead of an arbitrary timeout value. >> --- >> drivers/gpu/drm/virtio/virtgpu_drv.c | 15 +++++++++++++++ >> drivers/gpu/drm/virtio/virtgpu_drv.h | 1 + >> drivers/gpu/drm/virtio/virtgpu_vq.c | 23 +++++++++++++++++++++-- >> 3 files changed, 37 insertions(+), 2 deletions(-) >>=20 >> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virt= io/virtgpu_drv.c >> index a5ce96fb8a1d..e4fe5e0780f9 100644 >> --- a/drivers/gpu/drm/virtio/virtgpu_drv.c >> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c >> @@ -119,10 +119,24 @@ static int virtio_gpu_probe(struct virtio_device *= vdev) >> return ret; >> } >> =20 >> +/* >> + * Release pending virtqueue waits so the drm_dev_enter/exit() critical >> + * sections complete before drm_dev_unplug() blocks on synchronize_srcu= (). >> + */ >> +static void virtio_gpu_release_vqs(struct drm_device *dev) >> +{ >> + struct virtio_gpu_device *vgdev =3D dev->dev_private; >> + >> + vgdev->vqs_released =3D true; >> + wake_up_all(&vgdev->ctrlq.ack_queue); >> + wake_up_all(&vgdev->cursorq.ack_queue); >> +} >> + >> static void virtio_gpu_remove(struct virtio_device *vdev) >> { >> struct drm_device *dev =3D vdev->priv; >> =20 >> + virtio_gpu_release_vqs(dev); >> drm_dev_unplug(dev); >> drm_atomic_helper_shutdown(dev); >> virtio_gpu_deinit(dev); >> @@ -133,6 +147,7 @@ static void virtio_gpu_shutdown(struct virtio_device= *vdev) >> { >> struct drm_device *dev =3D vdev->priv; >> =20 >> + virtio_gpu_release_vqs(dev); >> /* stop talking to the device */ >> drm_dev_unplug(dev); >> } >> diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virt= io/virtgpu_drv.h >> index f17660a71a3e..0bd69a40857e 100644 >> --- a/drivers/gpu/drm/virtio/virtgpu_drv.h >> +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h >> @@ -235,6 +235,7 @@ struct virtio_gpu_device { >> =20 >> struct virtio_gpu_queue ctrlq; >> struct virtio_gpu_queue cursorq; >> + bool vqs_released; >> struct kmem_cache *vbufs; >> =20 >> atomic_t pending_commands; >> diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virti= o/virtgpu_vq.c >> index 67865810a2e7..8057a9b7356d 100644 >> --- a/drivers/gpu/drm/virtio/virtgpu_vq.c >> +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c >> @@ -396,7 +396,19 @@ static int virtio_gpu_queue_ctrl_sgs(struct virtio_= gpu_device *vgdev, >> if (vq->num_free < elemcnt) { >> spin_unlock(&vgdev->ctrlq.qlock); >> virtio_gpu_notify(vgdev); >> - wait_event(vgdev->ctrlq.ack_queue, vq->num_free >=3D elemcnt); >> + wait_event(vgdev->ctrlq.ack_queue, >> + vq->num_free >=3D elemcnt || vgdev->vqs_released); >> + /* >> + * Set by virtio_gpu_release_vqs() to unblock >> + * synchronize_srcu() wait in drm_dev_unplug(). >> + */ >> + if (vgdev->vqs_released) { >> + if (fence && vbuf->objs) >> + virtio_gpu_array_unlock_resv(vbuf->objs); >> + free_vbuf(vgdev, vbuf); >> + drm_dev_exit(idx); >> + return -ENODEV; >> + } >> goto again; >> } >> =20 >> @@ -566,7 +578,14 @@ static void virtio_gpu_queue_cursor(struct virtio_g= pu_device *vgdev, >> ret =3D virtqueue_add_sgs(vq, sgs, outcnt, 0, vbuf, GFP_ATOMIC); >> if (ret =3D=3D -ENOSPC) { >> spin_unlock(&vgdev->cursorq.qlock); >> - wait_event(vgdev->cursorq.ack_queue, vq->num_free >=3D outcnt); >> + wait_event(vgdev->cursorq.ack_queue, >> + vq->num_free >=3D outcnt || vgdev->vqs_released); >> + /* See comment in virtio_gpu_queue_ctrl_sgs(). */ >> + if (vgdev->vqs_released) { >> + free_vbuf(vgdev, vbuf); >> + drm_dev_exit(idx); >> + return; >> + } >> spin_lock(&vgdev->cursorq.qlock); >> goto retry; >> } else { > > What about other wait_event in the driver? Why only these? > > --=20 > Best regards, > Dmitry I see the command but can't find the corresponding bug. The email is sent to syzbot+HASH@syzkaller.appspotmail.com address but the HASH does not correspond to any known bug. Please double check the address.