> Wether these "other" interrupts are >prioritized or not i do not know....maybe somebody can throw >some light on it!!! I dont think atleast in x86 they are prioritized, the 8259A interrupt controller is definitely capable of prioritizing interrupts and it does this by checking its 'IN SERVICE REGISTER', but in Linux, (i think in the do_irq function), we clears the IN SERVICE REGISTER before calling the device specific ISRs, this essentially gives the interrupt controller the feeling that theinterrupt processing is over and it can interrupt the processor if there is another interrupt. correct me if i am wrong gop HTH, mandeep On Fri, 2004-10-01 at 17:23, mbrennan@xxxxxxxx wrote: > Hello! > > I'm reading Understanding the Linux Kernel, and I'm trying to understand > interrupts and exceptions properly. I wonder if I have understanded this > correctly, this is how I think it works, and I would appreciate if someone > could confirm that its right. > > So, is this correct? > > Linux's interrupts are interleaved, ie. they can be nested. That must mean > that interrupts are enabled when handling interrupts. Now the thing that > confuses me a little is that Linux uses interrupt gates, which clears the > IF flag, and disables interrupts. But it seems like Linux sets the IF flag > again before the actual handler. Is this to protect the code before the > handler from being interrupted? If so, why is this neccesary? > > When interrupts are disabled by masking the maskable interrupts, does that > mean that the CPU ignores the signal on the INTR pin. And when a IRQ is > masked on the PIC, does that mean that the PIC doesn't send any interrupt > to the CPU when that IRQ is raised? > In other words, the IF flag makes the CPU ignore all maskable interrupts, > while masking a particular IRQ, it prevents the interrupt from reaching > the CPU. > > When executing an interrupt handler, maskable interrupts are enabled but > the IRQ of the interrupt is masked out. Other interrupts may interrupt the > execution, but not the same as the one currently executed? > > Thank you! > > /Michael > > -- > Kernelnewbies: Help each other learn about the Linux kernel. > Archive: http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/ -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
