From nobody Fri Nov 14 18:19:10 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=quarantine dis=none) header.from=redhat.com ARC-Seal: i=1; a=rsa-sha256; t=1761592026; cv=none; d=zohomail.com; s=zohoarc; b=DEIpaTrlkOpPrtSoKvNn7GJ5+v5vqCvv3XzuO1m223PsziM/gykJpY1vDKeo4WKxF94ebJD/pxmJx0Uw/G/U9b6h48udFigm/Efd3ez8CFwbEi69tYODChKkhj2/qcTpHeoSmoOIYY2jhxaSjR4mn2dEPx2zFl9CCLDQsIiuXWE= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1761592026; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=QPQltLsvoOYR1EDvs5tOwznarOJoulthY/B2nh96bnM=; b=hb2jGW7yJlvj2NmqLMvu2gBgJIjLW5xuIRSHh2/R/WTJdsLL2UFZVkLiPYlEOZ2fo0+rVrZ02QPfnZCz171IOCUaGIkURJNb0NB85q1Ht/Vh5Qop+ypETCafPAB9cS9hTyI6qb/zpH35++2A3yPDNBpPVS8vnPqSm9Y6XoXT2vI= ARC-Authentication-Results: i=1; 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 header.from= (p=quarantine dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1761592026686630.0055613840401; Mon, 27 Oct 2025 12:07:06 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vDSXF-0006OY-Ej; Mon, 27 Oct 2025 15:05:43 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vDSX8-0006O7-Fp for qemu-devel@nongnu.org; Mon, 27 Oct 2025 15:05:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vDSX3-0003hS-0q for qemu-devel@nongnu.org; Mon, 27 Oct 2025 15:05:34 -0400 Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-7-QZqshLWaPBCQrJWuflMK3w-1; Mon, 27 Oct 2025 15:05:20 -0400 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 487621800451; Mon, 27 Oct 2025 19:05:19 +0000 (UTC) Received: from localhost (unknown [10.2.16.174]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4E9ED1955F1B; Mon, 27 Oct 2025 19:05:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761591922; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QPQltLsvoOYR1EDvs5tOwznarOJoulthY/B2nh96bnM=; b=clW1XrUTATwNGGg7eE7z0GZhL2WAZfkdyZkr2V4kgJGlmMY8Z6R4Fzo3XNk3jhaygD0s9g SYSYVi9nkW7hw9J2MD0lXHc4+Db9AOF17uoArUsLhOum0eSfo5Y2TJe8IPpexNMqjhWsrZ vkImud8/Kf+ZEkjUVGtP13B8db3BL04= X-MC-Unique: QZqshLWaPBCQrJWuflMK3w-1 X-Mimecast-MFC-AGG-ID: QZqshLWaPBCQrJWuflMK3w_1761591919 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Cc: Fam Zheng , "Michael S. Tsirkin" , Richard Henderson , Paolo Bonzini , qemu-block@nongnu.org, Fiona Ebner , Stefan Hajnoczi Subject: [PULL 1/1] hw/scsi: avoid deadlock upon TMF request cancelling with VirtIO Date: Mon, 27 Oct 2025 15:05:14 -0400 Message-ID: <20251027190514.36991-2-stefanha@redhat.com> In-Reply-To: <20251027190514.36991-1-stefanha@redhat.com> References: <20251027190514.36991-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 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=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1761592029667154100 Content-Type: text/plain; charset="utf-8" From: Fiona Ebner When scsi_req_dequeue() is reached via scsi_req_cancel_async() virtio_scsi_tmf_cancel_req() virtio_scsi_do_tmf_aio_context(), there is a deadlock when trying to acquire the SCSI device's requests lock, because it was already acquired in virtio_scsi_do_tmf_aio_context(). In particular, the issue happens with a FreeBSD guest (13, 14, 15, maybe more), when it cancels SCSI requests, because of timeout. This is a regression caused by commit da6eebb33b ("virtio-scsi: perform TMFs in appropriate AioContexts") and the introduction of the requests_lock earlier. To fix the issue, only cancel the requests after releasing the requests_lock. For this, the SCSI device's requests are iterated while holding the requests_lock and the requests to be cancelled are collected in a list. Then, the collected requests are cancelled one by one while not holding the requests_lock. This is safe, because only requests from the current AioContext are collected and acted upon. Originally reported by Proxmox VE users: https://bugzilla.proxmox.com/show_bug.cgi?id=3D6810 https://forum.proxmox.com/threads/173914/ Fixes: da6eebb33b ("virtio-scsi: perform TMFs in appropriate AioContexts") Suggested-by: Stefan Hajnoczi Signed-off-by: Fiona Ebner Message-id: 20251017094518.328905-1-f.ebner@proxmox.com [Changed g_list_append() to g_list_prepend() to avoid traversing the list each time. --Stefan] Signed-off-by: Stefan Hajnoczi --- hw/scsi/virtio-scsi.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c index d817fc42b4..93e87c459c 100644 --- a/hw/scsi/virtio-scsi.c +++ b/hw/scsi/virtio-scsi.c @@ -339,6 +339,7 @@ static void virtio_scsi_do_tmf_aio_context(void *opaque) SCSIDevice *d =3D virtio_scsi_device_get(s, tmf->req.tmf.lun); SCSIRequest *r; bool match_tag; + g_autoptr(GList) reqs =3D NULL; =20 if (!d) { tmf->resp.tmf.response =3D VIRTIO_SCSI_S_BAD_TARGET; @@ -374,10 +375,21 @@ static void virtio_scsi_do_tmf_aio_context(void *opaq= ue) if (match_tag && cmd_req->req.cmd.tag !=3D tmf->req.tmf.tag) { continue; } - virtio_scsi_tmf_cancel_req(tmf, r); + /* + * Cannot cancel directly, because scsi_req_dequeue() would de= adlock + * when attempting to acquire the request_lock a second time. = Taking + * a reference here is paired with an unref after cancelling b= elow. + */ + scsi_req_ref(r); + reqs =3D g_list_prepend(reqs, r); } } =20 + for (GList *elem =3D g_list_first(reqs); elem; elem =3D g_list_next(el= em)) { + virtio_scsi_tmf_cancel_req(tmf, elem->data); + scsi_req_unref(elem->data); + } + /* Incremented by virtio_scsi_do_tmf() */ virtio_scsi_tmf_dec_remaining(tmf); =20 --=20 2.51.0