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Subject: Re: [patch 2/4] lglock: introduce special lglock and brlock spin
 locks
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Nick Piggin <npiggin@suse.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Frank Mayhar <fmayhar@google.com>, John Stultz <johnstul@us.ibm.com>,
       Andi Kleen <ak@linux.intel.com>
In-Reply-To: <20100604072618.400686656@suse.de>
References: <20100604064307.737085373@suse.de>
	 <20100604072618.400686656@suse.de>
Content-Type: text/plain; charset="UTF-8"
Date: Fri, 04 Jun 2010 09:56:03 +0200
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Le vendredi 04 juin 2010 à 16:43 +1000, Nick Piggin a écrit :
> pièce jointe document texte brut (kernel-introduce-brlock.patch)
> This patch introduces "local-global" locks (lglocks). These can be used to:
> 
> - Provide fast exclusive access to per-CPU data, with exclusive access to
>   another CPU's data allowed but possibly subject to contention, and to provide
>   very slow exclusive access to all per-CPU data.
> - Or to provide very fast and scalable read serialisation, and to provide
>   very slow exclusive serialisation of data (not necessarily per-CPU data).
> 
> Brlocks are also implemented as a short-hand notation for the latter use
> case.
> 
> Thanks to Paul for local/global naming convention.
> 
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-fsdevel@vger.kernel.org
> Cc: Al Viro <viro@ZenIV.linux.org.uk>
> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> Cc: Frank Mayhar <fmayhar@google.com>,
> Cc: John Stultz <johnstul@us.ibm.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Signed-off-by: Nick Piggin <npiggin@suse.de>
> ---
>  include/linux/lglock.h |  165 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 165 insertions(+)
> 

IMHO some changes in Documentation/ would be needed

> 								\
> + void name##_global_lock(void) {					\
> +	int i;								\
> +	preempt_disable();						\
> +	rwlock_acquire(&name##_lock_dep_map, 0, 0, _RET_IP_);		\
> +	for_each_online_cpu(i) {					\

for_each_possible_cpu()

> +		arch_spinlock_t *lock;					\
> +		lock = &per_cpu(name##_lock, i);			\
> +		arch_spin_lock(lock);					\
> +	}								\
> + }									\
> + EXPORT_SYMBOL(name##_global_lock);					\
> +									\
> + void name##_global_unlock(void) {					\
> +	int i;								\
> +	rwlock_release(&name##_lock_dep_map, 1, _RET_IP_);		\
> +	for_each_online_cpu(i) {					\

for_each_possible_cpu()

> +		arch_spinlock_t *lock;					\
> +		lock = &per_cpu(name##_lock, i);			\
> +		arch_spin_unlock(lock);					\
> +	}								\
> +	preempt_enable();						\
> + }									\
> + EXPORT_SYMBOL(name##_global_unlock);					\
> +									\