Re: repeat a function after fixed time period

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On Wed, 23 Mar 2005, Arjan van de Ven wrote:



This kernel code should do just fine.



struct INFO {
     struct timer_list timer;            // For test timer
     atomic_t running;                   // Timer is running
     };

//-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
//
//   This stops the timer. This must NOT be called with a spin-lock
//   held.
//
static void stop_timer()
{
     if(atomic_read(&info->running))
     {
         atomic_dec(&info->running);

this is a race.

No, never. stop_timer() can be called at any time, even from
interrupt context. The last guy to touch info->running wins.
The logic works just perfectly.


         if(info->timer.function)
             del_timer(&info->timer);

you probably want del_timer_sync() here.


static void start_timer(void)
{
     if(!atomic_read(&info->running))
     {
         atomic_inc(&info->running);

same race.

No such race at all.




Cheers,
Dick Johnson
Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips).
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