Le 09-04-2006, Bernhard Walle <bernhard.walle@xxxxxx> a écrit :
> Hello,
>
> I'm experimenting about kernel preemption. If I understand it
> correctly, a process executing a syscall could be preempted by another
> process with a higher priority.
>
> I have a simple kernel module with a 10 seconds loop in the
> init_module() function. This function should be preemptible because
> it's the insmod process in the init_module system call.
>
> But another process with SCHED_FIFO (prio 99) isn't run until the init
> function exits.
>
> The code is
>
> int __init preempt_test_init(void)
> {
> unsigned long end;
>
> end = jiffies + HZ * 10; /* 10 seconds */
>
> pr_info("Preempt_count = %d\n", preempt_count());
> while (time_before(jiffies, end));
> pr_info("End\n");
> }
>
> and of the process
>
> memset(&parm, 0, sizeof (struct sched_param));
> parm.sched_priority = 99;
>
> err = sched_setscheduler(getpid(), SCHED_FIFO, &parm);
> if (err < 0) {
> perror("Cannot change scheduler");
> return 1;
> }
>
> while (true) {
> printf("Scheduled, count = %d\n", counter++);
> sleep(1);
> }
>
> Thanks!
In a personal email, you told me that you use VmWare to test this
code. You should test it without VmWare. I don't how the emulator works
but there must be some problems and process confusions. Is each process
a real unix process ... ?
Well try this code on a real linux environnement.
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