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    SubjectRe: pull request: wireless 2011-11-22
    From: Larry Finger <>
    Date: Tue, 22 Nov 2011 15:30:33 -0600

    > On 11/22/2011 03:13 PM, David Miller wrote:
    >> From: David Miller<>
    >> Date: Tue, 22 Nov 2011 16:05:11 -0500 (EST)
    >>> From: "John W. Linville"<>
    >>> 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"<>
    >>>>> 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.

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      Last update: 2011-11-22 22:45    [W:0.048 / U:81.972 seconds]
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