Hi Kashyap, Sending to the group this time. On Thu, Jan 20, 2011 at 11:00 PM, C K Kashyap <ckkashyap@xxxxxxxxx> wrote: > Hi, > I noticed that the flags register is being stored before doing 'cli' and > then restored after calling 'sti'. - eg. in local_irq_save and > local_irq_restore > Can someone tell me the scenario that is being guarded against by backing up > flags? The flags typically includes the interrupt status register. If you have nested calls to local_irq_save/restore, like follows assume interrupts are enabled here local_irq_save interrupts are now disabled local_irq_save interrupts should continue to be disabled local_irq_restore At this point interrupts should be restored to the state they were at save time (i.e. disabled) If you didn't save the flags, then you wouldn't know whether to enable or disable interrupts at this point. local_irq_restore At this point interrupts should be restored to the state they were at save time (i.e. enabled). Dave Hylands _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
