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https://github.com/cirosantilli/linux-kernel-module-cheat.git
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6420c31986
Improve GEM5 documentation in general. Fix documentation for x86 kernel module debugging example, fop_write had been made static, and use timer.ko instead of fops which is more reliable and fun.
48 lines
1.1 KiB
C
48 lines
1.1 KiB
C
/*
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Print the jiffies every second.
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Timers are callbacks that run when an interrupt happens, from the interrupt context itself.
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Therefore they produce more accurate timing than thread scheduling, which is more complex,
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but you can't do too much work inside of them.
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See also:
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- http://stackoverflow.com/questions/10812858/timers-in-linux-device-drivers
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- https://gist.github.com/yagihiro/310149
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*/
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#include <linux/jiffies.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/timer.h>
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/* We would normally mark this as static and give it a more generic name.
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* But let's do it like this this time for the sake of our GDB kernel module step debugging example. */
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void lkmc_timer_callback(struct timer_list *data);
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static unsigned long onesec;
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DEFINE_TIMER(mytimer, lkmc_timer_callback);
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void lkmc_timer_callback(struct timer_list *data)
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{
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pr_info("%u\n", (unsigned)jiffies);
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mod_timer(&mytimer, jiffies + onesec);
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}
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static int myinit(void)
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{
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onesec = msecs_to_jiffies(1000);
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mod_timer(&mytimer, jiffies + onesec);
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return 0;
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}
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static void myexit(void)
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{
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del_timer(&mytimer);
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}
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module_init(myinit)
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module_exit(myexit)
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MODULE_LICENSE("GPL");
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