Re: [PATCH 1/2] watchdog: dw_wdt: Use a mutex, not a spinlock

From: Doug Anderson
Date: Fri May 08 2015 - 00:01:20 EST


On Thu, May 7, 2015 at 6:47 PM, Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
> On 05/07/2015 03:09 PM, Doug Anderson wrote:
>> Right now the dw_wdt uses a spinlock to protect dw_wdt_open(). The
>> problem is that while holding the spinlock we call:
>> -> dw_wdt_set_top()
>> -> dw_wdt_top_in_seconds()
>> -> clk_get_rate()
>> -> clk_prepare_lock()
>> -> mutex_lock()
>> Locking a mutex while holding a spinlock is not allowed and leads to
>> warnings like "BUG: spinlock wrong CPU on CPU#1", among other
>> problems.
>> There's no reason to use a spinlock, so switch to a mutex.
>> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

As Dmitry pointed out in another context, and even better fix is to
just remove the spinlock altogether. I'll send up v2...

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