From mboxrd@z Thu Jan  1 00:00:00 1970
From: ben-linux@fluff.org (Ben Dooks)
Date: Tue, 19 Oct 2010 00:09:25 +0100
Subject: [PATCH] ARM: SAMSUNG: Bug fix spin_lock recursion in clk_enable()
	and	clk_disable()
In-Reply-To: <1286843980-23684-1-git-send-email-jc.lee@samsung.com>
References: <1286843980-23684-1-git-send-email-jc.lee@samsung.com>
Message-ID: <4CBCD3A5.5070701@fluff.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 12/10/10 01:39, Jaecheol Lee wrote:
> From: Minho Ban <mhban@samsung.com>
> 
> The clk_enable() and clk_disable() can be used process and ISR either.
> So spin_lock_irqsave should be used instead.
> 
> Signed-off-by: Minho Ban <mhban@samsung.com>
> Signed-off-by: Jaecheol Lee <jc.lee@samsung.com>
> ---
>  arch/arm/plat-samsung/clock.c |   12 ++++++++----
>  1 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/plat-samsung/clock.c b/arch/arm/plat-samsung/clock.c
> index e8d20b0..2a991a5 100644
> --- a/arch/arm/plat-samsung/clock.c
> +++ b/arch/arm/plat-samsung/clock.c
> @@ -138,31 +138,35 @@ void clk_put(struct clk *clk)
>  
>  int clk_enable(struct clk *clk)
>  {
> +	unsigned long flags;
> +
>  	if (IS_ERR(clk) || clk == NULL)
>  		return -EINVAL;
>  
>  	clk_enable(clk->parent);
>  
> -	spin_lock(&clocks_lock);
> +	spin_lock_irqsave(&clocks_lock, flags);
>  
>  	if ((clk->usage++) == 0)
>  		(clk->enable)(clk, 1);
>  
> -	spin_unlock(&clocks_lock);
> +	spin_unlock_irqrestore(&clocks_lock, flags);
>  	return 0;
>  }
>  
>  void clk_disable(struct clk *clk)
>  {
> +	unsigned long flags;
> +
>  	if (IS_ERR(clk) || clk == NULL)
>  		return;
>  
> -	spin_lock(&clocks_lock);
> +	spin_lock_irqsave(&clocks_lock, flags);
>  
>  	if ((--clk->usage) == 0)
>  		(clk->enable)(clk, 0);
>  
> -	spin_unlock(&clocks_lock);
> +	spin_unlock_irqrestore(&clocks_lock, flags);
>  	clk_disable(clk->parent);

I'm not sure, but I don't belive that the clk_ api has
ever been callable from non-sleepable contexts such as
interrupt handlers.

I would welcome RMK's response (or any other response)
about this issue?

Personally, given that some clk_ calls may sleep esp.
for pll enables, I would prefer to see this patch
dropped in favour of fixing the users.

-- 
Ben