From nobody Sat May 18 10:30:05 2024 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=fail; 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=fail(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 16389770811828.800725326799125; Wed, 8 Dec 2021 07:24:41 -0800 (PST) Received: from localhost ([::1]:43916 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1muyoA-0007qK-Gn for importer@patchew.org; Wed, 08 Dec 2021 10:24:38 -0500 Received: from eggs.gnu.org ([209.51.188.92]:51820) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1muymc-0006OD-Ls for qemu-devel@nongnu.org; Wed, 08 Dec 2021 10:23:02 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:52830) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1muyma-0003Kb-A9 for qemu-devel@nongnu.org; Wed, 08 Dec 2021 10:23:01 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-231-rvSzs-qnMM6Ygi-wdzXExA-1; Wed, 08 Dec 2021 10:22:55 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 049A08042A8; Wed, 8 Dec 2021 15:22:54 +0000 (UTC) Received: from localhost (unknown [10.39.194.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id A7CF85D6CF; Wed, 8 Dec 2021 15:22:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1638976979; 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; bh=N1Sizoha/xY5Hl6GltA0a5ZgL91v2k6Dt/fUT/WVB3Y=; b=HcRKOrrq5hKgdPO9PLG15f0u/j2MGTWWZ5n5IZ2a3WztvxEAdsvm+To70x9WvJ1/9rVyRV p23FO6LFYaidcCfSnDFiMCNL6NV+vizBkvR2piLYZdx4hHXkH0p+El4UwdC736ZjOKWwur N8n1cALL2xACGGIlmLrgFlNspwtah/Y= X-MC-Unique: rvSzs-qnMM6Ygi-wdzXExA-1 From: Stefan Hajnoczi To: qemu-devel@nongnu.org Subject: [PATCH] block/nvme: fix infinite loop in nvme_free_req_queue_cb() Date: Wed, 8 Dec 2021 15:22:46 +0000 Message-Id: <20211208152246.244585-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@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=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.619, 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=unavailable 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: , Cc: Kevin Wolf , Fam Zheng , qemu-block@nongnu.org, Hanna Reitz , Stefan Hajnoczi , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) X-ZM-MESSAGEID: 1638977082026100002 Content-Type: text/plain; charset="utf-8" When the request free list is exhausted the coroutine waits on q->free_req_queue for the next free request. Whenever a request is completed a BH is scheduled to invoke nvme_free_req_queue_cb() and wake up waiting coroutines. 1. nvme_get_free_req() waits for a free request: while (q->free_req_head =3D=3D -1) { ... trace_nvme_free_req_queue_wait(q->s, q->index); qemu_co_queue_wait(&q->free_req_queue, &q->lock); ... } 2. nvme_free_req_queue_cb() wakes up the coroutine: while (qemu_co_enter_next(&q->free_req_queue, &q->lock)) { ^--- infinite loop when free_req_head =3D=3D -1 } nvme_free_req_queue_cb() and the coroutine form an infinite loop when q->free_req_head =3D=3D -1. Fix this by checking q->free_req_head in nvme_free_req_queue_cb(). If the free request list is exhausted, don't wake waiting coroutines. Eventually an in-flight request will complete and the BH will be scheduled again, guaranteeing forward progress. Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daud=C3=A9 --- block/nvme.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block/nvme.c b/block/nvme.c index e4f336d79c..fa360b9b3c 100644 --- a/block/nvme.c +++ b/block/nvme.c @@ -206,8 +206,9 @@ static void nvme_free_req_queue_cb(void *opaque) NVMeQueuePair *q =3D opaque; =20 qemu_mutex_lock(&q->lock); - while (qemu_co_enter_next(&q->free_req_queue, &q->lock)) { - /* Retry all pending requests */ + while (q->free_req_head !=3D -1 && + qemu_co_enter_next(&q->free_req_queue, &q->lock)) { + /* Retry waiting requests */ } qemu_mutex_unlock(&q->lock); } --=20 2.33.1