I am implemnting a character device driver for uniprocessor system, kernel 2.4.7.
mydev_open is the implementation of open system call.
the devices are /dev/mydev1, /dev/mydev2, etc with minors starting at 0.
While a Process 1 opens mydev_open for /dev/mydev1, it will update the instance variable which is global in the driver.
Like,
instances = 0 ;
mydev_open() {
....
instances ++;
....
}
mydev_close () {
...
instances --;
...
}My doubt is that, in a uniprocessor system, shall I protect instances variable with a semaphore? I know that the kernel paths are non preemptible. Does it mean that unless the driver calls a schedule(), the kernel paths executions will not be interleaved?
Thanks Om.
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