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? There are many functions in the kernel that can be accessed with interrupts enabled or disabled. A function X has no handy way to know whether its caller or another function has already disabled interrupts. However if X unconditionally re-enables interrupts at the end of its body, a caller that has disabled interrupts prior to calling it will find that interrupts are enabled once X returns - something unexpected and unacceptable. local_irq_save and local_irq_restore ensure that interrupts are re-enabled by the function of the call stack that actually disabled them. Alex. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
