Return-path: <linux-wireless-owner@vger.kernel.org>
Received: from perches-mx.perches.com ([206.117.179.246]:40241 "EHLO
	labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
	id S1751674Ab2CSUwq (ORCPT <rfc822;linux-wireless@vger.kernel.org>);
	Mon, 19 Mar 2012 16:52:46 -0400
Message-ID: <1332190365.6525.10.camel@joe2Laptop> (sfid-20120319_215255_423729_C6C9DB42)
Subject: Re: [PATCH] rtlwifi: Preallocate USB read buffers and eliminate
 kalloc in read routine
From: Joe Perches <joe@perches.com>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: John W Linville <linville@tuxdriver.com>,
	linux-wireless@vger.kernel.org
Date: Mon, 19 Mar 2012 13:52:45 -0700
In-Reply-To: <4F6798C2.1000203@lwfinger.net>
References: <4f669d14.5MVnZ/K9sIFwYerB%Larry.Finger@lwfinger.net>
	 <1332125197.23125.41.camel@joe2Laptop> <4F6798C2.1000203@lwfinger.net>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Sender: linux-wireless-owner@vger.kernel.org
List-ID: <linux-wireless.vger.kernel.org>

On Mon, 2012-03-19 at 15:36 -0500, Larry Finger wrote:
> On 03/18/2012 09:46 PM, Joe Perches wrote:
> > On Sun, 2012-03-18 at 21:42 -0500, Larry Finger wrote:
> >> The current version of rtlwifi for USB operations uses kmalloc to
> >> acquire a 32-bit buffer for reading.
> > trivia:
> >> +++ wireless-testing-new/drivers/net/wireless/rtlwifi/usb.c
> > []
> >> @@ -955,6 +947,13 @@ int __devinit rtl_usb_probe(struct usb_i
> >>   		return -ENOMEM;
> >>   	}
> >>   	rtlpriv = hw->priv;
> >> +	rtlpriv->usb_data = kzalloc(RTL_USB_MAX_RX_COUNT * sizeof(u32),
> >> +				    GFP_KERNEL);
> >> +	if (!rtlpriv->usb_data) {
> >> +		RT_ASSERT(false, "USB data buffer allocation failed\n");
> > The RT_ASSERT isn't really necessary as kzalloc already
> > does a dump_stack on allocation failure.
> I thought it only dumped the stack when some form of kernel debugging was enabled.

<annoying wiseguy mode>
If by kernel debugging you mean enabling CONFIG_PRINTK,
then yes that's true...
<>

The kernel does a dump_stack on any k.alloc or v.alloc failure.

see: warn_alloc_failed in mm/page_alloc.c

You can suppress it with GFP_NOWARN.