Question about using spinlock to synchronize between kernel driver and an interrupt handler

[m silverstri]

Thanks Arun,

But why not just use mutex and remove the completion?
i.e. do this:

struct mutex dev_lock;

some_func()
{
mutex_lock(&dev_lock);
set_register_value


}

interrupt_handler(){
mutex_unloc(&dev_lock);
}

mutex_init(&dev_lock);
request_irq(interrupt_handler);

On Mon, Feb 3, 2014 at 1:54 AM, Arun KS <getarunks at gmail.com> wrote:
> Hi Silverstri,
>
>
> On Sun, Feb 2, 2014 at 1:19 PM, m silverstri
> <michael.j.silverstri at gmail.com> wrote:
>>
>> On Sat, Feb 1, 2014 at 5:34 AM, Josh Cartwright <joshc at eso.teric.us>
>> wrote:
>> > On Sat, Feb 01, 2014 at 01:32:49AM -0800, anish singh wrote:
>> >> On Sat, Feb 1, 2014 at 1:15 AM, m silverstri
>> >> <michael.j.silverstri at gmail.com> wrote:
>> >> > By driver code , I mean the code which set the register values and
>> >> > wait till the values is set (via an interrupt handler) before
>> >> > continues doing something else
>> >> ok so you are looking for below code:
>> >>
>> >>
>> >> some_func()
>> >> {
>> >> set_register_value
>> >> x_variable=0
>> >> wait_for_event*(x_variable);
>> >> }
>> >>
>> >> interrupt_handler(){
>> >> x_variable=1
>> >> wake_up();
>> >> }
>> >>
>> >> request_irq(interrupt_handler);
>> >
>> > Please investigate the usage of completions in your driver.  See
>> > include/linux/completion.h.  It sounds like it fits your usecase nicely.
>> >
>> >   Josh
>>
>> I have loooked at linux completion for my usecase
>> So I think I can do
>>
>> DECLARE_COMPLETION(my_completion);
>>
>> some_func()
>> {
>> set_register_value
>> wait_for_completion(my_completion);
>> }
>>
>> interrupt_handler(){
>> complete(my_completion);
>> }
>>
>> request_irq(interrupt_handler);
>>
>>
>> My question now is what if 1 kernel thread execute some_funct(), but
>> before interrupt_handler() get invoked (from HW), another kernel
>> thread executes some_func(). In essence, set_register_value is execute
>> twice before interrupt_handler() return once.
>
> Use a mutex_lock().
> So your code will be as follows:
>
> DECLARE_COMPLETION(my_completion);
> struct mutex dev_lock;
>
> some_func()
> {
> mutex_lock(&dev_lock);
> set_register_value
> wait_for_completion(my_completion);
> mutex_unloc(&dev_lock);
> }
>
> interrupt_handler(){
> complete(my_completion);
> }
>
> mutex_init(&dev_lock);
> request_irq(interrupt_handler);
>
> Thanks,
> Arun
>
>>
>>
>> how can I prevent another kernel thread from executing
>> "set_register_value()" when 1 is wait_for_completion?
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies at kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>