From patchwork Mon Nov 3 15:56:22 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Amos Kong X-Patchwork-Id: 5217821 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id B83ACC11AC for ; Mon, 3 Nov 2014 15:58:19 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id AFA0F2015E for ; Mon, 3 Nov 2014 15:58:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA24B2014A for ; Mon, 3 Nov 2014 15:58:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752910AbaKCP5y (ORCPT ); Mon, 3 Nov 2014 10:57:54 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60818 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752895AbaKCP5x (ORCPT ); Mon, 3 Nov 2014 10:57:53 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id sA3FuYIQ027697 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 3 Nov 2014 10:56:34 -0500 Received: from air.redhat.com (vpn1-115-59.nay.redhat.com [10.66.115.59]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id sA3FuLUw017635; Mon, 3 Nov 2014 10:56:31 -0500 From: Amos Kong To: virtualization@lists.linux-foundation.org Cc: kvm@vger.kernel.org, rusty@rustcorp.com.au, herbert@gondor.apana.org.au, m@bues.ch, mb@bu3sch.de, mpm@selenic.com, amit.shah@redhat.com, linux-kernel@vger.kernel.org Subject: [PATCH v4 2/6] hw_random: move some code out mutex_lock for avoiding underlying deadlock Date: Mon, 3 Nov 2014 23:56:22 +0800 Message-Id: <1415030186-18303-3-git-send-email-akong@redhat.com> In-Reply-To: <1415030186-18303-1-git-send-email-akong@redhat.com> References: <1415030186-18303-1-git-send-email-akong@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.26 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In next patch, we use reference counting for each struct hwrng, changing reference count also needs to take mutex_lock. Before releasing the lock, if we try to stop a kthread that waits to take the lock to reduce the referencing count, deadlock will occur. Signed-off-by: Amos Kong --- drivers/char/hw_random/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index b1b6042..a0905c8 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -474,12 +474,12 @@ void hwrng_unregister(struct hwrng *rng) } } if (list_empty(&rng_list)) { + mutex_unlock(&rng_mutex); unregister_miscdev(); if (hwrng_fill) kthread_stop(hwrng_fill); - } - - mutex_unlock(&rng_mutex); + } else + mutex_unlock(&rng_mutex); } EXPORT_SYMBOL_GPL(hwrng_unregister);