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SubjectRe: [PATCH 2.4.32] Fix AVM C4 ISDN card init problems with newer CPUs
Date
On Friday 04 August 2006 08:56, Willy Tarreau wrote:
> On Thu, Aug 03, 2006 at 06:56:15PM +0100, Alan Cox wrote:
> > Ar Iau, 2006-08-03 am 19:53 +0300, ysgrifennodd Jukka Partanen:
> > > AVM C4 ISDN NIC: Add three memory barriers, taken from 2.6.7,
> > > (they are there in 2.6.17.7 too), to fix module initialization
> > > problems appearing with at least some newer Celerons and
> > > Pentium III.
> >
> > Should be using cpu_relax() I think. Its a polled busy loop so you want
> > other CPU threads to run if possible.
>
> You mean like this ? Here's the patch for 2.6, I'll queue the same for 2.4
> if it's alright.
>
> > Alan
>
> Regards,
> Willy
>
> From 512d12bd7ce9c0a15dfd91a6f7c2970c92b3abdd Mon Sep 17 00:00:00 2001
> From: Willy Tarreau <w@1wt.eu>
> Date: Fri, 4 Aug 2006 08:50:10 +0200
> Subject: [PATCH] AVM C4 ISDN card : use cpu_relax() in busy loops
>
> As suggested by Alan, use cpu_relax() in 3 busy loops : "It's a
> polled busy loop so you want other CPU threads to run if possible".
>
> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
> drivers/isdn/hardware/avm/c4.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/isdn/hardware/avm/c4.c b/drivers/isdn/hardware/avm/c4.c
> index f7253b2..aee278e 100644
> --- a/drivers/isdn/hardware/avm/c4.c
> +++ b/drivers/isdn/hardware/avm/c4.c
> @@ -22,6 +22,7 @@ #include <linux/capi.h>
> #include <linux/kernelcapi.h>
> #include <linux/init.h>
> #include <asm/io.h>
> +#include <asm/processor.h>
> #include <asm/uaccess.h>
> #include <linux/netdevice.h>
> #include <linux/isdn/capicmd.h>
> @@ -150,6 +151,7 @@ static inline int wait_for_doorbell(avmc
> if (!time_before(jiffies, stop))
> return -1;
> mb();
> + cpu_relax();

cpu_relax() implies a memory barrier.

--
Greetings Michael.
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