CODEWITHSUNDEEP
timerlinux-kerneltimeoutlinux-device-driverkernel-module
RootPhoenix
RootPhoenix

Reputation: 1767

How to modify kernel timer_list timeout

I am implementing a timeout for some parameters in my kernel module.

So I am using struct timer_list and Associated API's to implement a 12 sec timer.

So as mentioned in the IBM developer Works guide for kernel timers I use:

struct timer_list my_timer;
init_timer_on_stack(&my_timer);

void tick_timer()
{
    my_timer.expires = jiffies + delay * HZ; //delay is global variable int = 12.
    my_timer.data=0;
    my_timer.function = my_timer_func;
    add_timer(&my_timer);
}

So each time my timer expires I do my work in my_timer_func and call tick_timer again to reset the timer.

Next, I would like to implement the delay as a sysctl entry. But the change should immediately call the tick_timer function and reset the timer with new delay. SO how can I detect this change and remove any current timer or reset it.

Should there be any kernel thread to detect the change in delay

Upvotes: 1

Views: 456

Answers (1)

Tsyvarev
Tsyvarev

Reputation: 66288

Kernel has no mechanism for detect changes in variables. Instead, you should perform corresponded actions before/after your code changes your variable.

When you add sysctl entry, you also set handler for it(ctl_table->proc_handler). This handler defines actions, which are executed when read/write method for entry is called. Standard proc_do* functions only set/get value of variable, so you should define your handler. Something like this:

int my_handler(struct ctl_table *table, int write,
     void __user *buffer, size_t *lenp, loff_t *ppos)
{
    // Call standard helper..
    int res = proc_dointvec(table, write, buffer, lenp, ppos);
    if(write && !res) { 
       // Additional actions on successfull write.
    }
    return res;
}

Modification of the timer's timeout can be performed using mod_timer function.

Upvotes: 1

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