Hi... 2009/6/24 Kostya B <bkostya@xxxxxxxxxxx>: > > > Dear list, > > Please help me to analyze the following scenario: > > By having a userspace process 'A' executing a system call. > Hardware interrupt happens. Do you think on exit from interrupt (irq_exit) > the context switch could take place? Yes it could, depending on the preemption model you pick...see below.... > Let's assume no softirq work is pending. > > (a) kernel is not preemptive then it would stay in the current kernel code path, which is executing the syscall on behalf of running task. > (b) kernel is preemptive What I am quite sure here is, in full preemptive kernel, after returning from interrupt handling, scheduler is allowed to pick new task to be executed. So, let's say scheduler has pick new task according to certain rules, context switch will happen. For voluntary preemption, perhaps you need to check the code by your own. In my point of view, after reading http://lwn.net/Articles/95334/ (probably not so relevant anymore), I have impression rescheduling also happen after returning from interrupt handler. > (c) with RT patch I have no hands on experience about RT patch. Also you need to specificly define whether you refer to hard or soft RT. I think in both RT style, the preemption might happen after returning from the interrupt. By doing that, scheduler might be able to pick the job that almost meet its deadline. regards, Mulyadi. -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
