On Fri, Aug 14, 2009 at 12:15 PM, Michael Blizek<michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > Hi! > > On 00:08 Fri 14 Aug , Mohammed Gamal wrote: > > ... > >> As far as I understood, Michi's answer explains why and when the >> kernel *can* get preempted, however what I really want to know is when >> and where kernel preemption is *triggered*. Please correct me if I did >> misunderstand anything. > > It is triggered by the timer interrupt. This is an interrupt which fires > periodically on configureable intervals. It does not only preempt the kernel, > but user space processes as well. If it fires, the kernel will enter the > scheduler and decide what to run next. In addition, IIRC: - every return from hard interrupt, either back to kernel space (if kernel level preemption is enabled) or to user space triggers preemption checking. - going back from kernel space to user space triggers preemption checking. -- regards, Mulyadi Santosa Freelance Linux trainer blog: the-hydra.blogspot.com -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
