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

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Date:   Tue, 26 Nov 2019 09:49:08 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     '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>,
        Peter Zijlstra <peterz@...radead.org>,
        Ashok Raj <ashok.raj@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>
CC:     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

From: Fenghua Yu
> Sent: 25 November 2019 19:43
> From: Peter Zijlstra <peterz@...radead.org>
> 
> Since "pwol_mask" is local and never exposed to concurrency, there is
> no need to set bit in pwol_mask by costly atomic operations.
> 
> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>  drivers/net/ethernet/broadcom/b44.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
> index 97ab0dd25552..5738ab963dfb 100644
> --- a/drivers/net/ethernet/broadcom/b44.c
> +++ b/drivers/net/ethernet/broadcom/b44.c
> @@ -1520,7 +1520,7 @@ static int b44_magic_pattern(u8 *macaddr, u8 *ppattern, u8 *pmask, int offset)
> 
>  	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.
The way pmask is used definitely wanst a u32[] not a u64[] one.

	David

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