ic. thanks a lot for explanation. so these are level sensitive interrupt. i need to find a hw book now... Ming On Mon, 2005-08-15 at 11:47 -0700, Bryan Henderson wrote: > >so it is possible that both card raise intr quicker than isr run, then > >both isr will do mmio and go ahead, but then what is > > > >device 1 raise intr > >device 2 isr run and not belong to it, so quit, but before it clear intr > >and quit > >device 2 raise intr > >device 1 isr run and handle device 1, then clear intr and quit. > > > >then device 2 intr lost? > > As these are level sensitive interrupt requests, they can't be lost. As > long as Device 2 is requesting service, > the shared IRQ is raised and at some point Linux will call Device 2's > interrupt handler. Either the first level IRQ handler will keep calling > all the interrupt handlers that service that IRQ until the IRQ subsides, > or it will unmask the IRQ, causing an immediate new interrupt and the > first level interrupt handler runs again and calls all the device drivers > again. > > The raised IRQ says, "Device 1 or Device 2 needs service." The device > drivers clear the service request of the individual device; as long as > either device requests service, the IRQ is raised. > > -- > Bryan Henderson IBM Almaden Research Center > San Jose CA Filesystems > > - > : send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
