From: Larry Finger <Larry.Finger@xxxxxxxxxxxx> Date: Tue, 22 Nov 2011 15:30:33 -0600 > On 11/22/2011 03:13 PM, David Miller wrote: >> From: David Miller<davem@xxxxxxxxxxxxx> >> Date: Tue, 22 Nov 2011 16:05:11 -0500 (EST) >> >>> From: "John W. Linville"<linville@xxxxxxxxxxxxx> >>> Date: Tue, 22 Nov 2011 15:56:55 -0500 >>> >>>> On Tue, Nov 22, 2011 at 03:14:29PM -0500, David Miller wrote: >>>>> From: "John W. Linville"<linville@xxxxxxxxxxxxx> >>>>> Date: Tue, 22 Nov 2011 14:35:05 -0500 >>>>> >>>>>> Here is the latest batch of fixes intended for 3.2. This includes a >>>>>> correction for a user-visible error in mac80211's debugfs info, a fix >>>>>> for a potential memory corrupter in prism54, an endian fix for rt2x00, >>>>>> an endian fix for mac80211, a fix for a NULL derefernce in cfg80211, a >>>>>> locking fix and a deadlock fix for p54spi, and a pair of rt2x00 fixes >>>>>> for handling some spurious interrupts that hardware can generate. >>>>>> >>>>>> Please let me know if there are problems! >>>>> >>>>> The rt2800pci change doesn't look correct. >>>>> >>>>> If the IRQ line is shared with another device, this change will make >>>>> it >>>>> never see interrupts. Once you say "IRQ_HANDLED" the IRQ dispatch >>>>> stops processing the interrupt handler list. >>>> >>>> I thought this at first as well. But looking at the code in >>>> kernel/irq/handle.c doesn't support that conclusion. In fact, every >>>> handler gets invoked no matter what they all return. All of the irq >>>> handler return values are ORed together and passed to note_interrupt. >>>> Only if every irq handler returns IRQ_NONE does the code in >>>> kernel/irq/spurious.c start getting involved. >>>> >>>> Anyway, this seems to be safe even for shared interrupts. That said, >>>> this is a bit ugly. But it makes a serious difference in performance >>>> for those afflicted with this issue. >>> >>> It just means that we won't notice spurious interrupts if the device >>> sharing the line with rt2800pci generates one. >>> >>> This change is wrong. >> >> BTW, look at it this way, if what you say is true John then what's the >> point >> in returning any specific value at all? >> >> Everyone can just return IRQ_HANDLED and everything would just work. >> >> But you know that's not the case, and that it's important that this >> value >> is returned accurately. > > I was trying to find the thread that reported the improvement in > performance with this change, but failed. Is it possible that their > change just papered over an interrupt storm from some other device > that shared that interrupt? It doesn't fix a performance problem, it fixes a problem wherein the IRQ line is disabled by the generic IRQ code because all handlers return IRQ_NONE. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
