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Date: Wed, 21 Dec 2011 14:12:29 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>, mc@linux.vnet.ibm.com,
        Stephen Boyd <sboyd@codeaurora.org>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, Nick Piggin <npiggin@kernel.dk>,
        david@fromorbit.com, Maciej Rutecki <maciej.rutecki@gmail.com>
Subject: Re: [PATCH] VFS: br_write_lock locks on possible CPUs other than
 online CPUs
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On Thu, 22 Dec 2011 02:45:29 +0530
"Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> wrote:

off-topic, but the lockdep stuff in include/linux/lglock.h
(LOCKDEP_INIT_MAP and DEFINE_LGLOCK_LOCKDEP) appears to be dead code.

> --- a/include/linux/lglock.h
> +++ b/include/linux/lglock.h
> @@ -22,6 +22,7 @@
>  #include <linux/spinlock.h>
>  #include <linux/lockdep.h>
>  #include <linux/percpu.h>
> +#include <linux/cpu.h>
>  
>  /* can make br locks by using local lock for read side, global lock for write */
>  #define br_lock_init(name)	name##_lock_init()
> @@ -72,9 +73,31 @@
>  
>  #define DEFINE_LGLOCK(name)						\
>  									\
> + DEFINE_SPINLOCK(name##_cpu_lock);					\
> + cpumask_t name##_cpus __read_mostly;					\
>   DEFINE_PER_CPU(arch_spinlock_t, name##_lock);				\
>   DEFINE_LGLOCK_LOCKDEP(name);						\
>  									\

also off-topic: we can't define a static lglock with this macro.