Peter Zijlstra wrote: > On Fri, 2010-03-26 at 10:20 +0100, Ingo Molnar wrote: > > * Russell King <rmk@xxxxxxxxxxxxxxxx> wrote: > > > > > On Fri, Mar 26, 2010 at 12:06:44AM -0000, Thomas Gleixner wrote: > > > > The following patch series removes the IRQF_DISABLED functionality > > > > from the core interrupt code and runs all interrupt handlers with > > > > interrupts disabled. > > > > > > As was covered in previous discussions, what about drivers such as SMC91x > > > which take a long time to retrieve packets from the hardware? Always running > > > handlers with IRQs disabled will kill things such as serial on these > > > platforms. > > > > As long as it's rare (which it is) i dont see a problem: you can enable > > interrupts in the handler by using local_irq_enable(), like the IDE PIO > > drivers do. That way it's documented a bit better as well, because it shows > > the precise source of the latency, with a big comment explaining it, etc. > > Or alternatively, use threaded interrupts for such slow hardware. What is the latency of threaded interrupts these days, compared with non-threaded interrupts? Slow hardware is quite sensitive to increases in latency. Obviously not a problem for the sources of latency: it's a problem for the irq which is _sensitive_ to latency caused by the other one. That is typically a serial port or something. But the benefit of kernel-settable interrupt priorities (i.e. due to the threads) may be worth it even for serial ports. I would love to see some measurements comparing with and without. -- Jamie -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
