From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id B13CD35C680 for ; Tue, 8 Sep 2026 16:16:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788884179; cv=none; b=dVM1xzKWN03GpPWew/fKVo26N27A8vW4hS95HxeSGrRt9u9k7jN9XH+2U8QXW1btG6hq2De0nj5mXxNrvpSAyq3fOm/ZPk/S3R2McasRLlRvA9fRXXst3lI//MPOd9NK7TWzjNuez8IeruT5mZ29UAJlxZNvyHL2Nx6K/TE6OIA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788884179; c=relaxed/simple; bh=W86j1xmuLlz2bk41yXWceX/GDhYI2NYm1k/krLylX4M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PG3vkahnlpvGMtqA8ZAA4EhZ6BbFwU8qr/tfXoTy8+KtJqgHCPu/5VbX349bGBqD8ID+f9oP9+Sz7H/l/SSQYdbH5vC742KHkSAX+ypFZKPpEEcPJ0MBSArfTWhc2fDZgR6YrI+4qgr7C3eOQEyiU2/C+hLYm73mg+1pglGMHO4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=Qh8sgSR2; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="Qh8sgSR2" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 355081476; Tue, 8 Sep 2026 09:16:13 -0700 (PDT) Received: from localhost (unknown [10.2.196.114]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 76E233F7B4; Tue, 8 Sep 2026 09:16:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1788884176; bh=W86j1xmuLlz2bk41yXWceX/GDhYI2NYm1k/krLylX4M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Qh8sgSR2twbUctxTPL7/+iYnMnoN4URVKwArsPBGM/VyK9vQf92Fce8nkCqEgTUB/ G9DhPh4RC259GqtINnAUa3906GZ7KK1Y2aAXUMv6Cxzua6FF23/iK06U2Rkz8n560k B/CHzhK2DuOl73avp3FjFYsFMewTAP/L28DTPpJo= Date: Tue, 8 Sep 2026 17:16:14 +0100 From: Leo Yan To: yingchao Cc: Suzuki K Poulose , Alexander Shishkin , Mike Leach , James Clark , Mathieu Poirier , Miaoqian Lin , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, qinyungao@kylinsec.com.cn Subject: Re: [PATCH] coresight: syscfg: fix deadlock on device registration failure Message-ID: <20260908161614.GA200420@e132581.arm.com> References: <604ED754D4669F40+20260825014717.2346-1-dengyingchao@kylinsec.com.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <604ED754D4669F40+20260825014717.2346-1-dengyingchao@kylinsec.com.cn> On Tue, Aug 25, 2026 at 09:47:17AM +0800, yingchao wrote: > diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c > index 2bfdd7b45e49..d0e7e4720e46 100644 > --- a/drivers/hwtracing/coresight/coresight-syscfg.c > +++ b/drivers/hwtracing/coresight/coresight-syscfg.c > @@ -1210,8 +1210,14 @@ static int cscfg_create_device(void) > dev->init_name = "cs_system_cfg"; > > err = device_register(dev); > - if (err) > + if (err) { > + /* put_device() triggers cscfg_dev_release() which takes > + * cscfg_mutex, so drop the lock first to avoid deadlocking. > + */ > + mutex_unlock(&cscfg_mutex); > put_device(dev); > + return err; > + } As module init and exit are serialized by the kernel, I don't think we need the mutex to protect the allocation and freeing of cscfg_mgr. The mutex should only be used for exclusively access cscfg_mgr. So how about the change below? ---8<--- diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index 2bfdd7b45e49..2dd0b29f44e4 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -1173,27 +1173,21 @@ struct device *cscfg_device(void) /* Must have a release function or the kernel will complain on module unload */ static void cscfg_dev_release(struct device *dev) { - mutex_lock(&cscfg_mutex); kfree(cscfg_mgr); cscfg_mgr = NULL; - mutex_unlock(&cscfg_mutex); } /* a device is needed to "own" some kernel elements such as sysfs entries. */ static int cscfg_create_device(void) { struct device *dev; - int err = -ENOMEM; - - mutex_lock(&cscfg_mutex); - if (cscfg_mgr) { - err = -EINVAL; - goto create_dev_exit_unlock; - } + int err; cscfg_mgr = kzalloc_obj(struct cscfg_manager); if (!cscfg_mgr) - goto create_dev_exit_unlock; + return -ENOMEM; + + mutex_lock(&cscfg_mutex); /* initialise the cscfg_mgr structure */ INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list); @@ -1204,6 +1198,8 @@ static int cscfg_create_device(void) cscfg_mgr->load_state = CSCFG_NONE; raw_spin_lock_init(&cscfg_mgr->sysfs_store_lock); + mutex_unlock(&cscfg_mutex); + /* setup the device */ dev = cscfg_device(); dev->release = cscfg_dev_release; @@ -1213,8 +1209,6 @@ static int cscfg_create_device(void) if (err) put_device(dev); -create_dev_exit_unlock: - mutex_unlock(&cscfg_mutex); return err; }