[PATCH] ARM: SAMSUNG: Bug fix spin_lock recursion in clk_enable() and clk_disable()

[Jassi Brar]

On Tue, Oct 19, 2010 at 8:09 AM, Ben Dooks <ben-linux at fluff.org> wrote:
> On 12/10/10 01:39, Jaecheol Lee wrote:
>> From: Minho Ban <mhban at 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 at samsung.com>
>> Signed-off-by: Jaecheol Lee <jc.lee at 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.

I tend to agree.
I would like to know any such case where enabling/disabling of some
clock is so urgent as to require doing from ISR and not from a tasklet
scheduled from ISR.
Also let us not make it impossible in future to switch to common clock api
by Jeremy Kerr, that doesn't allow calls from IRQ context.