Hi Bernd Sorry for the late reply. I have tried to test your user space test program and the kernel module inside my Qemu virtual machine. And the result is...there is no delay inside the user space test program. The loop is still counting while the kernel module is correctly busy waiting for 10 seconds (10*HZ). IMHO, this concludes, something is missing/wrong in your kernel configuration. Here is my kernel config related to kernel preemption: # CONFIG_PREEMPT_NONE is not set # CONFIG_PREEMPT_VOLUNTARY is not set CONFIG_PREEMPT=y # CONFIG_PREEMPT_BKL is not set CONFIG_DEBUG_PREEMPT=y After comparing with yours, I believe you must try to set CONFIG_PREEMPT_BKL as "n". I am not sure what is the correlation between Big kernel Lock and busy waiting (using time_after()/time_before()), but it is worth to test. good luck... regards Mulyadi -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
