Hi, On Thu, Jan 19, 2012 at 7:26 AM, Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx> wrote: > Hi again :) > > On Thu, Jan 19, 2012 at 16:03, Darshan Ghumare > <darshan.ghumare@xxxxxxxxx> wrote: >> What if, there is one process which is in middle of a syscall which has >> infinite loop in it received SIGKILL & there are no other processes in the >> system? > > infinite loop such as "for(;;)" ? well as long as it doesn't disable > or masked out the timer interrupt, sooner or later timer interrupt > will kick in. It then followed by the usual tick handler. Inside it, > IIRC, will provoke the current running process to check queued signal > and handle it. If the process was in an infinite loop in user space, what Mulyadi says is true. If it were a real-time process in an infinite loop then it might very well be unkillable (unless there is a higher priority thread which can do the killing). My understanding is that in kernel space signals only get handled when you run into code which specifically deals with signals. All of the syscalls are wrapped with such code. So, if you're in an infinite loop in kernel space, then you're in essentially the same situation as doing a non-interruptible down which never completes. If the kernel were to kill the process just because a preemption occurred (while in kernel space) then you would very often be killing processes which are currently holding a semaphore or something and leaving the kernel in a potentially unstable state. There is always at least one runnable thread, called the idle thread. There is an idle thread for each CPU. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
