On 11/9/05, Bahadir Balban <bilgehan.balban@xxxxxxxxx> wrote: > Hi, > > I have some basic questions. Answering just yes or no should suffice > for me. If we say there are 3 levels of execution context: > > 1) Process context > 2) Bottom-Half context > 3) Irq context > Yes, correct ! > Is it correct to say that; > > 1) An in-interrupt context cannot sleep but it can be preempted if the > irqs are enabled. (Examples: inside a non-SA_INTERRUPT interrupt > handler or a tasklet) > Yes, this is what I know too ! > Spinlocks: > 2) No matter what context you are in, by acquiring a spinlock, > preemption is *always* disabled, to cover for the *always possible* > case of another process scheduling and deadlocking on the lock. > Yes, thats what the spin_lock code do (means disabling preemption) > 3) No matter what context you're in, *if, and only if* your spinlock > is shared with BH and/or Irq contexts, you disable them on the current > CPU, for they may interrupt yours, and deadlock on your spinlock. > I won't able to got what you want to say/ask ? > 4) Disabling of contexts for a spinlock is to protect against > deadlocks from the current CPU, whereas the spinlock itself is to > protect against races across CPUs. Does this also imply, the runqueue > of a CPU would never be balanced when a context on that CPU holds a > spinlock? > I can't say about this ! -- Fawad Lateef -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
