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[91.13.120.243]) by smtp.gmail.com with ESMTPSA id r14-20020aa7cfce000000b0043a4de1d421sm1134425edy.84.2022.07.14.07.30.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Jul 2022 07:30:49 -0700 (PDT) Received: from localhost.daheim ([127.0.0.1]) by debian64.daheim with esmtp (Exim 4.96) (envelope-from ) id 1oBxyj-0006LN-2D; Thu, 14 Jul 2022 16:30:49 +0200 Message-ID: <5d4c944e-005e-a443-cb87-230c4e097f93@gmail.com> Date: Thu, 14 Jul 2022 16:30:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.0.2 Subject: Re: [PATCH v2] p54: add missing parentheses in p54_flush() Content-Language: de-DE, en-US To: Rustam Subkhankulov Cc: Kalle Valo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Alexey Khoroshilov , ldv-project@linuxtesting.org References: <20220714134831.106004-1-subkhankulov@ispras.ru> From: Christian Lamparter In-Reply-To: <20220714134831.106004-1-subkhankulov@ispras.ru> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/07/2022 15:48, Rustam Subkhankulov wrote: > The assignment of the value to the variable total in the loop > condition must be enclosed in additional parentheses, since otherwise, > in accordance with the precedence of the operators, the conjunction > will be performed first, and only then the assignment. > > Due to this error, a warning later in the function after the loop may > not occur in the situation when it should. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Signed-off-by: Rustam Subkhankulov > Fixes: 0d4171e2153b ("p54: implement flush callback") For reference: This is the "warning" the commit message talks about: | WARN(total, "tx flush timeout, unresponsive firmware"); | } // this is right at the end of the p54_flush() function from what I can tell, the difference between: | while ((total = p54_flush_count(priv) && i--)) { and | while ((total = p54_flush_count(priv)) && i--) { boils down to what that "total" ends up being after the while() has run through. In the original code it can either be 0 (for everything is ok) or 1 (still pending - this is bad / firmware is on the fritz). In the patched version "total" will be 0 or the value of p54_flush_count(priv). I think both the current and the patched version behave the same way and produce the same output. However I think (since the variable is named "total") the returned value of p54_flush_count() is indeed more precise here. Acked-by: Christian Lamparter > --- > drivers/net/wireless/intersil/p54/main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/wireless/intersil/p54/main.c b/drivers/net/wireless/intersil/p54/main.c > index a3ca6620dc0c..8fa3ec71603e 100644 > --- a/drivers/net/wireless/intersil/p54/main.c > +++ b/drivers/net/wireless/intersil/p54/main.c > @@ -682,7 +682,7 @@ static void p54_flush(struct ieee80211_hw *dev, struct ieee80211_vif *vif, > * queues have already been stopped and no new frames can sneak > * up from behind. > */ > - while ((total = p54_flush_count(priv) && i--)) { > + while ((total = p54_flush_count(priv)) && i--) { > /* waste time */ > msleep(20); > }