linux-kernel - Re: [PATCH] kernel/cpu: Distinct name for cpu_hotplug.dep

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Date:	Fri, 5 Aug 2016 11:26:25 +0100
From:	Chris Wilson <chris@...is-wilson.co.uk>
To:	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc:	Linux kernel development <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	"Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
	intel-gfx@...ts.freedesktop.org, trivial@...nel.org
Subject: Re: [PATCH] kernel/cpu: Distinct name for cpu_hotplug.dep_map

On Thu, Jun 09, 2016 at 02:48:39PM +0300, Joonas Lahtinen wrote:
> Use distinctive name for cpu_hotplug.dep_map to avoid the actual
> cpu_hotplug.lock appearing as cpu_hotplug.lock#2 in lockdep splats.
> 
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> Cc: intel-gfx@...ts.freedesktop.org
> Cc: trivial@...nel.org
> Acked-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
> ---
> This time CC'ing trivial@...nel.org too in the hopes of finally getting this in.
> ---
>  kernel/cpu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/cpu.c b/kernel/cpu.c
> index d948e44..d74199d 100644
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -155,7 +155,7 @@ static struct {
>  	.wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
>  	.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
>  #ifdef CONFIG_DEBUG_LOCK_ALLOC
> -	.dep_map = {.name = "cpu_hotplug.lock" },
> +	.dep_map = STATIC_LOCKDEP_MAP_INIT("cpu_hotplug.dep_map", &cpu_hotplug.dep_map),
>  #endif
>  };


Going by

        /*
         * Static locks do not have their class-keys yet - for them the key
         * is the lock object itself:
         */
        if (unlikely(!lock->key))
                lock->key = (void *)lock;

this is the right choice for .key (as lock here is the dep_map).

Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre