On 1/23/07, Rajat Jain <rajat.noida.india@xxxxxxxxx> wrote:
On 1/23/07, sandeep lahane <sandeep.lahane@xxxxxxxxx> wrote: > I dont know much about SMP scheduling but after thinking a while I came up with > following inference, please correct me if I am wrong. > > If the ISR and the interrupted process are sharing the stack i.e. of > the ISR doesnt have its own seperate stack in that case moving the > interrupted process will be difficult since lot of book keeping will > be required. Also this would be a fragile situation with chances of > data corruption. > > But as far as I know, an ISR can have a separate stack also, this is > configurable. > In this case, moving the interrupted process to another cpu will be > easier/feasible than before. > > Regards, > Sandeep. > > > > On 1/23/07, Rick Brown <rick.brown.3@xxxxxxxxx> wrote: > > Hi, > > > > If an executing process is interrupted by an interrupt, is it ensured > > that it won't get transferred to another idle CPU in the system?? > > > > This would mean that despite the fact that a CPU is idle in the > > system, still the process will wait untill the ISR finishes its > > execution? > > The ISR is not a SEPARATE process. When it executes, for the scheduler it is the same process (which was interrupted). In other words, the fact that ISR has started execution putting the process on hold is not known to scheduler. Now given this, why would scheduler want to move a RUNNING process to a different CPU? Somebody please CMIIMW Regards, Rajat
Rajat, I think Rick wants to know how the scheduling is done in case of SMP machines. What I gathered from his question is, even though it is a SMP environment, if the interrupted process is not moved to another cpu which is idle then this suboptimal utilization of resources. So next obvious question is, is it possible to move the interrupted process to another cpu? This I tried to answer in my previous post depending upon whether the stack is shared or not. So hypothetically( or actually? ) the scheduler should move the interrupted process to another idle cpu for optimal utilization. Actually how this is done only an expert on the list can tell us. Regards, Sandeep. -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
