linux-kernel - Re: [RFC][PATCH 6/7] lockdep: Maintain rw

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Date:	Mon, 18 Apr 2011 21:37:38 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC][PATCH 6/7] lockdep: Maintain rw_state entries in locklist

On Sun, Apr 17, 2011 at 11:45:11AM +0200, Peter Zijlstra wrote:
> From: Gautham R Shenoy <ego@...ibm.com>
> 
> The dependencies are currently maintained using a structure named
> locklist. For a dependency A --> B, it saves B's lock_class in an
> entry that would be linked to A's locks_after list.
> 
> However, in order to make use of the split chains introduced in the
> previous patch, we need to enhance this infrastructure to save the
> read/write states of A and B for each dependency such that we might
> distinguish between the read and write chains.
> 
> Signed-off-by: Gautham R Shenoy <ego@...ibm.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  include/linux/lockdep.h |    6 ++++++
>  kernel/lockdep.c        |   23 +++++++++++++++++------
>  2 files changed, 23 insertions(+), 6 deletions(-)
>
> @@ -1690,6 +1694,8 @@ check_prev_add(struct task_struct *curr,
>  		if (entry->dep_class == hlock_class(next)) {
>  			if (distance == 1)
>  				entry->distance = 1;
> +			entry->this_lock_rw_state |= prev->rw_state;
> +			entry->dep_lock_rw_state |= next->rw_state;

If we could do this and return,

>  			return 2;
>  		}
>  	}
> @@ -1697,19 +1703,24 @@ check_prev_add(struct task_struct *curr,
>  	if (!trylock_loop && !save_trace(&trace))
>  		return 0;
>  
> +	list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
> +		if (entry->dep_class == hlock_class(prev)) {
> +			entry->this_lock_rw_state |= next->rw_state;
> +			entry->dep_lock_rw_state |= prev->rw_state;
> +		}
> +	}
> +

Do we have any change to do above?

Or am I missing something?

Thanks,
Yong
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