linux-kernel - Re: [PATCH 2/2] lockdep: print lock name for lockdep_init

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Date:	Thu, 17 Nov 2011 14:02:15 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	tom.leiming@...il.com
Cc:	mingo@...e.hu, a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] lockdep: print lock name for lockdep_init_error

On Thu, Nov 17, 2011 at 01:34:32PM +0800, tom.leiming@...il.com wrote:
> From: Ming Lei <tom.leiming@...il.com>
> 
> This patch prints the name of the lock which is acquired
> before lockdep_init is called, so that user can easily find
> which lock trigged the lockdep init error warning.

Should we care about that?

I think lockdep_init() called early enough give more hint.
Such as be the first C function called by arch.

Thanks,
Yong

> 
> This patch also removes the lockdep_init_error message
> of "Arch code didn't call lockdep_init() early enough?" since
> lockdep_init is called in arch independent code now.
> 
> Signed-off-by: Ming Lei <tom.leiming@...il.com>
> ---
>  kernel/lockdep.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> index 4e7e672..8141317 100644
> --- a/kernel/lockdep.c
> +++ b/kernel/lockdep.c
> @@ -430,6 +430,7 @@ unsigned int max_lockdep_depth;
>   * about it later on, in lockdep_info().
>   */
>  static int lockdep_init_error;
> +static const char *lock_init_error;
>  static unsigned long lockdep_init_trace_data[20];
>  static struct stack_trace lockdep_init_trace = {
>  	.max_entries = ARRAY_SIZE(lockdep_init_trace_data),
> @@ -651,6 +652,7 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
>  	if (unlikely(!lockdep_initialized)) {
>  		lockdep_init();
>  		lockdep_init_error = 1;
> +		lock_init_error = lock->name;
>  		save_stack_trace(&lockdep_init_trace);
>  	}
>  #endif
> @@ -3965,7 +3967,8 @@ void __init lockdep_info(void)
>  
>  #ifdef CONFIG_DEBUG_LOCKDEP
>  	if (lockdep_init_error) {
> -		printk("WARNING: lockdep init error! Arch code didn't call lockdep_init() early enough?\n");
> +		printk("WARNING: lockdep init error! lock-%s was acquired"
> +			"before lockdep_init\n", lock_init_error);
>  		printk("Call stack leading to lockdep invocation was:\n");
>  		print_stack_trace(&lockdep_init_trace, 0);
>  	}
> -- 
> 1.7.5.4
> 
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