From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753163AbeA1CNW (ORCPT ); Sat, 27 Jan 2018 21:13:22 -0500 Received: from mail-pf0-f195.google.com ([209.85.192.195]:36935 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751251AbeA1CNV (ORCPT ); Sat, 27 Jan 2018 21:13:21 -0500 X-Google-Smtp-Source: AH8x225XCsAwOVm2N1JjxRETCV6FWJHeTlNml6eDgpqxRmtBjPEZi3ZUCgyKZAOgK7mN3IAyD6LQdg== Subject: Re: [PATCH] block: aoenet: Replace GFP_ATOMIC with GFP_KERNEL in aoenet_rcv To: Ed Cashin Cc: ed.cashin@acm.org, linux-kernel@vger.kernel.org References: <1516959434-829-1-git-send-email-baijiaju1990@gmail.com> <219E4594-88B1-4501-A897-9A4B3296163B@cashinworks.com> From: Jia-Ju Bai Message-ID: Date: Sun, 28 Jan 2018 10:12:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <219E4594-88B1-4501-A897-9A4B3296163B@cashinworks.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/1/28 1:48, Ed Cashin wrote: > If the tool cannot tell whether the protected state is manipulated by *another* piece of code called in atomic context, then it's insufficient. > >> On Jan 26, 2018, at 4:37 AM, Jia-Ju Bai wrote: >> >> After checking all possible call chains to aoenet_rcv(), >> my tool finds that aoenet_rcv() is never called in atomic context, >> namely never in an interrupt handler or holding a spinlock. >> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL. >> >> This is found by a static analysis tool named DCNS written by myself. >> >> Signed-off-by: Jia-Ju Bai >> --- >> drivers/block/aoe/aoenet.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/block/aoe/aoenet.c b/drivers/block/aoe/aoenet.c >> index 63773a9..d5fff7a 100644 >> --- a/drivers/block/aoe/aoenet.c >> +++ b/drivers/block/aoe/aoenet.c >> @@ -138,7 +138,7 @@ static int __init aoe_iflist_setup(char *str) >> if (dev_net(ifp) != &init_net) >> goto exit; >> >> - skb = skb_share_check(skb, GFP_ATOMIC); >> + skb = skb_share_check(skb, GFP_KERNEL); >> if (skb == NULL) >> return 0; >> if (!is_aoe_netif(ifp)) >> -- >> 1.7.9.5 >> >> Sorry, I find my report is false positive after I manually check the code. aoenet_rcv() is used as function pointer via "->func", and it is called in dev_queue_xmit_nit() in net/core/dev.c. dev_queue_xmit_nit() calls a rcu_read_lock() before it calls pt_prev->func(). Thus it is right to use GFP_ATOMIC in aoenet_rcv(). Sorry again for my incorrect report... Thanks, Jia-Ju Bai