linux-kernel - Re: [PATCH] Convert tlbstate_lock spin_lock to raw_spin

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Date:	Mon, 8 Sep 2008 19:45:43 +0530
From:	"Sujit Karataparambil" <sjt.kar@...il.com>
To:	unlisted-recipients:; (no To-header on input)
Cc:	linux-rt-users@...r.kernel.org
Subject: Re: [PATCH] Convert tlbstate_lock spin_lock to raw_spin_lock

Chirag,

  Kindly understand what xavier is trying to do. He is Trying to disable smp.
The RT - Linux Code is dependent on the mutex lock to perform some
soft/hard real time processing. This is an problem with the mutex lock.

Kindly check with some one before signing off patches.

Thanks,
Sujit


On 9/8/08, Chirag Jog <chirag@...ux.vnet.ibm.com> wrote:
> * xavier droubay <xavier.droubay@...il.com> [2008-09-08 03:06:51]:
>
> > Hello,
> >
> > I experienced this "rtmutex.c:743" known bug with rt3 patch, using
> >
> >  http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.26.3.tar.bz2
> >  http://rt.et.redhat.com/download/patch-2.6.26.3-rt3.bz2
> >
> > I compiled this kernel with the "make-kpkg" debian utility.
> >
> > I first compiled this kernel with NO SMP, NO HIGHMEM, and partial ACPI
> > (without fan, processor, ... modules). Attached file
> > "config-2.6.26.3-rt3lowlty.frwr.gz".
> > I didn't experience any problem with this kernel.
> >
> > I then enabled SMP and HIGHMEM, and experienced  "rtmutex.c:743" BUG.
> > Attached files
> > "config-2.6.26.3-rt3rt-smp-hm.gz" and  "dmesg.gz" for some BUGGY message.
> >
> >
> > I have seen somewhere on the archive, that some people still
> > experienced problems with SMP.
> > I guess no fix has been done from rt3 to rt7 patch. Can you confirm?
> >
> > If so, which recent kernel should I use in order to get smp and rt
> > running without problems?
> >
> This simple patch should solve the above problem. Seeing the config, its
> seems to be a 32bit box.
>
>
> It convert tlbstate_lock spin_lock to raw_spin_lock.
> Preemption has already been disabled, hence this change shouldn't
> affect latency numbers.
>
>
> Signed-Off-By: Chirag <chirag@...ux.vnet.ibm.com>
>
>
> diff --git a/arch/x86/kernel/tlb_32.c b/arch/x86/kernel/tlb_32.c
> index 9bb2363..228849c 100644
> --- a/arch/x86/kernel/tlb_32.c
> +++ b/arch/x86/kernel/tlb_32.c
> @@ -23,7 +23,7 @@ DEFINE_PER_CPU(struct tlb_state, cpu_tlbstate)
>  static cpumask_t flush_cpumask;
>  static struct mm_struct *flush_mm;
>  static unsigned long flush_va;
> -static DEFINE_SPINLOCK(tlbstate_lock);
> +static DEFINE_RAW_SPINLOCK(tlbstate_lock);
>
>  /*
>  * We cannot call mmdrop() because we are in interrupt context,
>
>
>
> --
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