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    Subject[090/205] genirq: Deal with desc->set_type() changing desc->chip
    2.6.34-stable review patch.  If anyone has any objections, please let us know.


    From: Thomas Gleixner <>

    commit 4673247562e39a17e09440fa1400819522ccd446 upstream.

    The set_type() function can change the chip implementation when the
    trigger mode changes. That might result in using an non-initialized
    irq chip when called from __setup_irq() or when called via
    set_irq_type() on an already enabled irq.

    The set_irq_type() function should not be called on an enabled irq,
    but because we forgot to put a check into it, we have a bunch of users
    which grew the habit of doing that and it never blew up as the
    function is serialized via desc->lock against all users of desc->chip
    and they never hit the non-initialized irq chip issue.

    The easy fix for the __setup_irq() issue would be to move the
    irq_chip_set_defaults(desc->chip) call after the trigger setting to
    make sure that a chip change is covered.

    But as we have already users, which do the type setting after
    request_irq(), the safe fix for now is to call irq_chip_set_defaults()
    from __irq_set_trigger() when desc->set_type() changed the irq chip.

    It needs a deeper analysis whether we should refuse to change the chip
    on an already enabled irq, but that'd be a large scale change to fix
    all the existing users. So that's neither stable nor 2.6.35 material.

    Reported-by: Esben Haabendal <>
    Signed-off-by: Thomas Gleixner <>
    Cc: Benjamin Herrenschmidt <>
    Cc: linuxppc-dev <>
    Signed-off-by: Greg Kroah-Hartman <>

    kernel/irq/manage.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/kernel/irq/manage.c
    +++ b/kernel/irq/manage.c
    @@ -440,6 +440,9 @@ int __irq_set_trigger(struct irq_desc *d
    desc->status &= ~(IRQ_LEVEL | IRQ_TYPE_SENSE_MASK);
    desc->status |= flags;
    + if (chip != desc->chip)
    + irq_chip_set_defaults(desc->chip);

    return ret;

     \ /
      Last update: 2010-07-30 20:27    [W:0.022 / U:32.876 seconds]
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