netdev - Re: [PATCH] smc91c92_cs : add a spinlock to avoid race condition

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Message-Id: <20160818.230055.1587442048794416891.davem@davemloft.net>
Date:   Thu, 18 Aug 2016 23:00:55 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     vaishali.thakkar@...cle.com
Cc:     andrianov@...ras.ru, mugunthanvnm@...com, a@...table.cc,
        felipe.balbi@...ux.intel.com, fw@...len.de, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] smc91c92_cs : add a spinlock to avoid race condition

From: Vaishali Thakkar <vaishali.thakkar@...cle.com>
Date: Fri, 19 Aug 2016 10:11:32 +0530

> 
> 
> On Friday 19 August 2016 09:37 AM, David Miller wrote:
>> From: Pavel Andrianov <andrianov@...ras.ru>
>> Date: Tue, 16 Aug 2016 16:39:06 +0300
>> 
>>> smc_reset may be executed in parallel with timer function media_check.
>>> To avoid data race in smc_set_xcvr a spinlock was added.
>>>
>>> Found by Linux Driver Verification project (linuxtesting.org).
>>>
>>> Signed-off-by: Pavel Andrianov <andrianov@...ras.ru>
>> 
>> This is not sufficient.
>> 
>> You have to block basically the entire function, because both
>> smc_reset and media_check program the bank selection so could
>> corrupt eachother's register accesses.
> 
> Hmm, but then there is a use of udelay as well. Would it be still
> fine to acquire a spinlock on whole function?

I don't know, but what I'm telling you is that you have to execute
register programming these two functions do atomically so that the
bank selection doesn't check get changed midstream.