From patchwork Fri Nov 4 01:27:50 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Larry Finger X-Patchwork-Id: 621702 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 86530C433FE for ; Fri, 4 Nov 2022 01:28:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230254AbiKDB2A (ORCPT ); Thu, 3 Nov 2022 21:28:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229461AbiKDB16 (ORCPT ); Thu, 3 Nov 2022 21:27:58 -0400 Received: from mail-oa1-x29.google.com (mail-oa1-x29.google.com [IPv6:2001:4860:4864:20::29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5385423392; Thu, 3 Nov 2022 18:27:57 -0700 (PDT) Received: by mail-oa1-x29.google.com with SMTP id 586e51a60fabf-12c8312131fso4172088fac.4; Thu, 03 Nov 2022 18:27:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:sender:from:to:cc:subject:date:message-id:reply-to; bh=aUilUaHJkRjMTuKpx9KuulcmPnQFwe0ZTOEMgpM9EUs=; b=Qiuj1zxH72t4rljyyB3fSEkfn0epewXXoN357R0R6Usp3EKlWrx8iU6hpHUzfKpX1N jWUvsrLP7T+/T1HTqFmsPXuwFA3OhGOVpq/6hknV2wHSHf8vxvD0SjqSU9ikQYMusbVh Ibvt/VUaZO27SjIcQQsqhhHansMDWkRhoZJ25wlaEJFLerIHLY9Z6gt6gBWracbEq52v WyLK4J9IOWlBKdFWafyeUCtKH3Grw4/GJa2RKMtb5uDabXtgzXtRP9PcMO11bAgO+rcE 8vVYN3Y5hRUttjbnXz/13kwYZdkqigq9lG1nsPlZIePUhTXp23fp7wrjIrx9Cim5/XWG SHNQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:sender:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=aUilUaHJkRjMTuKpx9KuulcmPnQFwe0ZTOEMgpM9EUs=; b=cFiQjEvUumk5ghW4GWmY+37rM48BwHcDg8M2BNAClxyUxVo3wjuXkw2x+MRS8bOKgD wUcOU/gKupzfEc9gaVEkEZ2nnw6vYJUHZq6PlMGI9vuwroVobBtl2FbH/Mu8uv9PGTe5 tnuv4rXrxOMezr/l1FtHTwZwr3wtcZqHv6OanqkyTC1N1VsVJhnoxY0nveJMnm2ZONZK zeoWl9WlLkdpoQWI0uH7E93yEcxScziMAz67+hgOyR+xfHVQFfUB8cV76AUPMe2VHTaD LqOBcFNpnBNpeWpN7YIMnCODbpdq79p6DH6VsfldU/mXGDZQEOgn/Ah5GbzNHUi3tA7K 9Row== X-Gm-Message-State: ACrzQf3FeyRszoUeUQ6DM8M0Zh/RidMcxTk8v5GBFLPUwffAfWQnoNQD 8lxaEga3lngW+qkMsECFl1U= X-Google-Smtp-Source: AMsMyM7mnS5ut6p2YgNYUONLq0d80He/REUIRQ+G4m7m1O1dcQUT/Jn8NnVdFxbGwgr+wi1xKLrmPg== X-Received: by 2002:a05:6870:3414:b0:13c:787e:15ba with SMTP id g20-20020a056870341400b0013c787e15bamr19114631oah.164.1667525276643; Thu, 03 Nov 2022 18:27:56 -0700 (PDT) Received: from localhost.localdomain ([216.130.59.33]) by smtp.gmail.com with ESMTPSA id b6-20020a9d6b86000000b0066c75a2643asm924675otq.66.2022.11.03.18.27.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 18:27:56 -0700 (PDT) Sender: Larry Finger From: Larry Finger To: gregkh@linuxfoundation.org Cc: phil@philpotter.co.uk, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, Larry Finger , Randy Dunlap Subject: [PATCH v2] staging: rtl8192e: Fix divide fault when calculating beacon age Date: Thu, 3 Nov 2022 20:27:50 -0500 Message-Id: <20221104012750.2076-1-Larry.Finger@lwfinger.net> X-Mailer: git-send-email 2.38.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org When the configuration parameter CONFIG_HZ is less that 100, the compiler generates an error as follows: ../drivers/staging/rtl8192e/rtllib_wx.c: In function 'rtl819x_translate_scan': ../drivers/staging/rtl8192e/rtllib_wx.c:220:57: warning: division by zero [-Wdiv-by-zero] 220 | (jiffies - network->last_scanned) / (HZ / 100)); | ^ In file included from ../include/linux/skbuff.h:45, from ../include/linux/if_ether.h:19, from ../include/linux/etherdevice.h:20, from ../drivers/staging/rtl8192e/rtllib_wx.c:18: ../drivers/staging/rtl8192e/rtllib_wx.c: In function 'rtllib_wx_get_scan': ../drivers/staging/rtl8192e/rtllib_wx.c:261:70: warning: division by zero [-Wdiv-by-zero] 261 | (jiffies - network->last_scanned) / | In fact, is HZ is not a multiple of 100, the calculation will be wrong, but it will compile correctly. The fix is to get rid of the (HZ / 100) portion. To decrease any round-off errors, the compiler is forced to perform the 100 * jiffies-difference before dividing by HZ. This patch is only compile tested. Reported-by: Randy Dunlap Acked-by: Randy Dunlap # build-tested Signed-off-by: Larry Finger Tested-by: Philipp Hortmann --- v2 - some commit log lines are shortened - add space after * operator --- drivers/staging/rtl8192e/rtllib_wx.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/staging/rtl8192e/rtllib_wx.c b/drivers/staging/rtl8192e/rtllib_wx.c index da2c41c9b92f..217426ee2e92 100644 --- a/drivers/staging/rtl8192e/rtllib_wx.c +++ b/drivers/staging/rtl8192e/rtllib_wx.c @@ -217,7 +217,7 @@ static inline char *rtl819x_translate_scan(struct rtllib_device *ieee, p = custom; p += scnprintf(p, MAX_CUSTOM_LEN - (p - custom), " Last beacon: %lums ago", - (jiffies - network->last_scanned) / (HZ / 100)); + (100 * (jiffies - network->last_scanned)) / HZ); iwe.u.data.length = p - custom; if (iwe.u.data.length) start = iwe_stream_add_point_rsl(info, start, stop, @@ -258,8 +258,8 @@ int rtllib_wx_get_scan(struct rtllib_device *ieee, escape_essid(network->ssid, network->ssid_len), network->bssid, - (jiffies - network->last_scanned) / - (HZ / 100)); + (100 * (jiffies - network->last_scanned)) / + HZ); } spin_unlock_irqrestore(&ieee->lock, flags);