linux-kernel - Re: [PATCH -rt] rt-slab: fix cpu inconsistency case

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Date:	Thu, 20 Mar 2008 15:32:35 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH -rt] rt-slab: fix cpu inconsistency case


Hi Hiroshi,

Thanks for looking into it. I'll take a deeper look at it later, but
first I have a few nitpicks with the patch.

On Thu, 20 Mar 2008, Hiroshi Shimamoto wrote:
>
> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
> ---
>  mm/slab.c |   18 +++++++++---------
>  1 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 4bf6ca8..7beb378 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -138,8 +138,8 @@
>   *
>   * (On PREEMPT_RT, these are NOPs, but we have to drop/get the irq locks.)
>   */
> -# define slab_irq_disable_nort()	local_irq_disable()
> -# define slab_irq_enable_nort()		local_irq_enable()
> +# define slab_irq_disable_nort(cpu)	slab_irq_disable(cpu)
> +# define slab_irq_enable_nort(cpu)	slab_irq_enable(cpu)

This is the !PREEMPT_RT version. It should stay as is (with the
exception of ignoring the "cpu" variable. [ (void)cpu; ? ]

#define slab_irq_disable_nort(cpu) \
	do { \
		(void)cpu;  \
		local_irq_disable(); \
	} while(0)


>  # define slab_irq_disable_rt(flags)	do { (void)(flags); } while (0)
>  # define slab_irq_enable_rt(flags)	do { (void)(flags); } while (0)
>  # define slab_spin_lock_irq(lock, cpu) \
> @@ -160,8 +160,8 @@ DEFINE_PER_CPU_LOCKED(int, slab_irq_locks) = { 0, };
>  	do { slab_irq_enable(cpu); (void) (flags); } while (0)
>  # define slab_irq_disable_rt(cpu)	slab_irq_disable(cpu)
>  # define slab_irq_enable_rt(cpu)	slab_irq_enable(cpu)
> -# define slab_irq_disable_nort()	do { } while (0)
> -# define slab_irq_enable_nort()		do { } while (0)
> +# define slab_irq_disable_nort(cpu)	do { } while (0)
> +# define slab_irq_enable_nort(cpu)	do { } while (0)

And these are the PREEMPT_RT version. So basically, this patch is a nop
for PREEMPT_RT. I doubt it will solve your bug ;-)


-- Steve

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