linux-kernel - Re: [v2 2/4] platform: (TS-5500) add GPIO support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4E5D2F55.2000608@zytor.com>
Date:	Tue, 30 Aug 2011 11:43:33 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
CC:	Mark Brown <broonie@...nsource.wolfsonmicro.com>, x86@...nel.org,
	Jerome Oufella <jerome.oufella@...oirfairelinux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [v2 2/4] platform: (TS-5500) add GPIO support

On 08/30/2011 11:39 AM, Vivien Didelot wrote:
> On Mon, 29 Aug 2011 23:11:33 +0100,
> Mark Brown <broonie@...nsource.wolfsonmicro.com> wrote:
>> On Fri, Aug 26, 2011 at 07:40:25PM -0400, Vivien Didelot wrote:
>>> +	bitno = line_to_bit_map[offset];
>>> +
>>> +	mutex_lock(&drvdata->gpio_lock);
>>> +	byte = inb(ioaddr);
>>> +	mutex_unlock(&drvdata->gpio_lock);
>>
>> Do you really need the lock to do a read?
> 
> Is there any chance for this function to be preempted before reading the
> register, allowing a call to ts5500_gpio_direction_output to occur
> before ts5500_gpio_get is completed?
> 

Wrapping an atomic operation in a mutex makes no sense no matter how you
slice it...
	
	-hpa

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/