-----Original Message----- From: kernelnewbies-bounces@xxxxxxxxxxxxxxxxx [mailto:kernelnewbies-bounces@xxxxxxxxxxxxxxxxx] On Behalf Of Vincenzo Scotti Sent: Friday, March 20, 2015 4:20 PM To: kernelnewbies@xxxxxxxxxxxxxxxxx Subject: Kernel thread scheduling Hello, I am actually studying kernel threads, and I have some doubts about them. Let's take for example this snippet of code static int thread_function(void *data) { while (!kthread_should_stop()) { schedule(); } pr_err("Stopped"); return 0; } This way it works just fine, and waits until I call kthread_stop on it. But if I comment out that schedule() call, it just hangs my system when I load it (it is part of a module). I see that the loop-schedule-wakeup pattern is used among all the others kernel threads. But I don't get why I need to call the scheduler explicitly. I know that the kernel is fully preemptible, and in my interpretation I thought that it could stop every running thread, even in kernel space, using a timer-based interrupt handler, to give cpu to other threads. Doesn't this pattern resemble a voluntary preemption model? Where am I wrong? Are you sure your kernel is configured with kernel preemption on? It is a configurable option. Grep for PREEMPT in your .config file. Jeff _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
