linux-kernel - Re: [PATCH v2 1/4] drivers/net/b44: Change to non-atomic bit operations

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Message-ID: <20191204151940.GY2844@hirez.programming.kicks-ass.net>
Date:   Wed, 4 Dec 2019 16:19:40 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     'Fenghua Yu' <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v2 1/4] drivers/net/b44: Change to non-atomic bit
 operations

On Tue, Nov 26, 2019 at 09:49:08AM +0000, David Laight wrote:

> >  	memset(ppattern + offset, 0xff, magicsync);
> >  	for (j = 0; j < magicsync; j++)
> > -		set_bit(len++, (unsigned long *) pmask);
> > +		__set_bit(len++, (unsigned long *)pmask);
> 
> While this stops the misaligned locks, the code is still horribly borked on BE systems.

Quite so.

> The way pmask is used definitely wanst a u32[] not a u64[] one.

Not sure, the code seems fairly consistent in using u8[].

And I suppose we can write the above like:

	pmask[len >> 3] |= BIT(len & 7); len++;

instead.