linux-kernel - Re: [PATCH] locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP

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Date:   Tue, 12 Dec 2017 16:15:28 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     peterz@...radead.org, mingo@...nel.org
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-block@...r.kernel.org,
        kernel-team@....com, david@...morbit.com, tytso@....edu,
        willy@...radead.org, torvalds@...ux-foundation.org,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH] locking/lockdep: Make CONFIG_LOCKDEP_CROSSRELEASE and
 CONFIG_LOCKDEP_COMPLETIONS optional

+cc david@...morbit.com
+cc tytso@....edu
+cc willy@...radead.org
+cc torvalds@...ux-foundation.org
+cc amir73il@...il.com

On 12/12/2017 4:11 PM, Byungchul Park wrote:
> At the moment, it's rather premature to enable
> CONFIG_LOCKDEP_CROSSRELEASE and CONFIG_LOCKDEP_COMPLETIONS by default,
> because we face a lot of false positives for now since all locks and
> waiters are not classified properly yet.
> 
> Until most of them get annotated properly, it'd be better to be optional.
> 
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
>   lib/Kconfig.debug | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 2689b7c..bc099f1 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1092,8 +1092,6 @@ config PROVE_LOCKING
>   	select DEBUG_MUTEXES
>   	select DEBUG_RT_MUTEXES if RT_MUTEXES
>   	select DEBUG_LOCK_ALLOC
> -	select LOCKDEP_CROSSRELEASE
> -	select LOCKDEP_COMPLETIONS
>   	select TRACE_IRQFLAGS
>   	default n
>   	help
> @@ -1164,7 +1162,9 @@ config LOCK_STAT
>   	 (CONFIG_LOCKDEP defines "acquire" and "release" events.)
>   
>   config LOCKDEP_CROSSRELEASE
> -	bool
> +	bool "Lock debugging: enable cross-locking checks in lockdep"
> +	depends on PROVE_LOCKING
> +	default n
>   	help
>   	 This makes lockdep work for crosslock which is a lock allowed to
>   	 be released in a different context from the acquisition context.
> @@ -1174,7 +1174,10 @@ config LOCKDEP_CROSSRELEASE
>   	 detector, lockdep.
>   
>   config LOCKDEP_COMPLETIONS
> -	bool
> +	bool "Lock debugging: allow completions to use deadlock detector"
> +	depends on PROVE_LOCKING
> +	select LOCKDEP_CROSSRELEASE
> +	default n
>   	help
>   	 A deadlock caused by wait_for_completion() and complete() can be
>   	 detected by lockdep using crossrelease feature.
> 

-- 
Thanks,
Byungchul