From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id AF9A4A04A2; Wed, 19 Jan 2022 23:01:38 +0100 (CET) Received: from [217.70.189.124] (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 6CA77411B8; Wed, 19 Jan 2022 23:01:38 +0100 (CET) Received: from stargate.chelsio.com (stargate.chelsio.com [12.32.117.8]) by mails.dpdk.org (Postfix) with ESMTP id 389F2411B6 for ; Wed, 19 Jan 2022 23:01:36 +0100 (CET) Received: from localhost (scalar.blr.asicdesigners.com [10.193.185.94]) by stargate.chelsio.com (8.14.7/8.14.7) with ESMTP id 20JM1YXt008960; Wed, 19 Jan 2022 14:01:35 -0800 Date: Thu, 20 Jan 2022 03:31:21 +0530 From: Rahul Lakkireddy To: Ferruh Yigit Cc: dev@dpdk.org Subject: Re: [PATCH] net/cxgbe: fix dangling pointer for gcc12 Message-ID: <20220119220120.GA3070@chelsio.com> References: <20220117143630.3044764-1-ferruh.yigit@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220117143630.3044764-1-ferruh.yigit@intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi Ferruh, On Monday, January 01/17/22, 2022 at 14:36:30 +0000, Ferruh Yigit wrote: > Observed with: gcc (GCC) 12.0.0 20220116 (experimental) > > In file included from ../lib/eal/linux/include/rte_os.h:14, > from ../lib/eal/include/rte_common.h:28, > from ../lib/eal/include/rte_log.h:25, > from ../lib/ethdev/rte_ethdev.h:164, > from ../lib/ethdev/ethdev_driver.h:18, > from ../drivers/net/cxgbe/base/t4vf_hw.c:6: > In function ‘t4_os_atomic_add_tail’, > inlined from ‘t4vf_wr_mbox_core’ at ../drivers/net/cxgbe/base/t4vf_hw.c:115:2: > ../drivers/net/cxgbe/base/adapter.h:742:9: error: storing the address of local variable ‘entry’ in ‘((struct mbox_list *)adapter)[96].tqh_last’ [-Werror=dangling-pointer=] > 742 | TAILQ_INSERT_TAIL(head, entry, next); > | ^~~~~~~~~~~~~~~~~ > ../drivers/net/cxgbe/base/t4vf_hw.c: In function ‘t4vf_wr_mbox_core’: > ../drivers/net/cxgbe/base/t4vf_hw.c:86:27: note: ‘entry’ declared here > 86 | struct mbox_entry entry; > | ^~~~~ > ../drivers/net/cxgbe/base/t4vf_hw.c:86:27: note: ‘adapter’ declared here > > It is a valid compiler warning, make local variable a global one. > > Signed-off-by: Ferruh Yigit > > --- > > Fix is done in a quickest way, mainly to report the issue, > please feel free to suggest another solution for the build error. > --- Thanks for reporting this issue. The intention of this code is to use the address of the local variable stored on stack to serialize access from multiple threads. This address is used only within the scope of this function and is not accessed from outside. I'm also stumped on why this warning is not showing up inside t4_wr_mbox_meat_timeout() in t4_hw.c, which also has similar code. Nevertheless, I've sent a patch at [1] to dynamically allocate/free the memory instead and fix the warning. [1] https://mails.dpdk.org/archives/dev/2022-January/232816.html Thanks, Rahul > drivers/net/cxgbe/base/t4vf_hw.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/cxgbe/base/t4vf_hw.c b/drivers/net/cxgbe/base/t4vf_hw.c > index 561d759dbc0d..b42c4e78eba9 100644 > --- a/drivers/net/cxgbe/base/t4vf_hw.c > +++ b/drivers/net/cxgbe/base/t4vf_hw.c > @@ -83,7 +83,7 @@ int t4vf_wr_mbox_core(struct adapter *adapter, > > u32 mbox_ctl = T4VF_CIM_BASE_ADDR + A_CIM_VF_EXT_MAILBOX_CTRL; > __be64 cmd_rpl[MBOX_LEN / 8]; > - struct mbox_entry entry; > + static struct mbox_entry entry; > unsigned int delay_idx; > u32 v, mbox_data; > const __be64 *p; > -- > 2.34.1 >