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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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