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    Subject[tip:irq/core] genirq: Use IRQ_BITMAP_BITS as search size in irq_alloc_descs()
    Commit-ID:  ed4dea6e0e33a3e58d8b77b775a8f0e433e7a005
    Gitweb: http://git.kernel.org/tip/ed4dea6e0e33a3e58d8b77b775a8f0e433e7a005
    Author: Yinghai Lu <yinghai@kernel.org>
    AuthorDate: Sat, 19 Feb 2011 11:07:37 -0800
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Mon, 21 Feb 2011 21:20:00 +0100

    genirq: Use IRQ_BITMAP_BITS as search size in irq_alloc_descs()

    The runtime expansion of nr_irqs does not take into account that
    bitmap_find_next_zero_area() returns "start" + size in case the search
    for an matching zero area fails. That results in a start value which
    can be completely off and is not covered by the following
    expand_nr_irqs() and possibly outside of the absolute limit. But we
    use it without further checking.

    Use IRQ_BITMAP_BITS as the limit for the bitmap search and expand
    nr_irqs when the start bit is beyond nr_irqs. So start is always
    pointing to the correct area in the bitmap. nr_irqs is just the limit
    for irq enumerations, not the real limit for the irq space.

    [ tglx: Let irq_expand_nr_irqs() take the new upper end so we do not
    expand nr_irqs more than necessary. Made changelog readable ]

    Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    LKML-Reference: <4D6014F9.8040605@kernel.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    ---
    kernel/irq/irqdesc.c | 15 ++++++++-------
    1 files changed, 8 insertions(+), 7 deletions(-)

    diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
    index 394ab6a..dbccc79 100644
    --- a/kernel/irq/irqdesc.c
    +++ b/kernel/irq/irqdesc.c
    @@ -207,11 +207,11 @@ struct irq_desc * __ref irq_to_desc_alloc_node(unsigned int irq, int node)
    return NULL;
    }

    -static int irq_expand_nr_irqs(unsigned int cnt)
    +static int irq_expand_nr_irqs(unsigned int nr)
    {
    - if (nr_irqs + cnt > IRQ_BITMAP_BITS)
    + if (nr > IRQ_BITMAP_BITS)
    return -ENOMEM;
    - nr_irqs += cnt;
    + nr_irqs = nr;
    return 0;
    }

    @@ -298,7 +298,7 @@ static inline int alloc_descs(unsigned int start, unsigned int cnt, int node)
    return start;
    }

    -static int irq_expand_nr_irqs(unsigned int cnt)
    +static int irq_expand_nr_irqs(unsigned int nr)
    {
    return -ENOMEM;
    }
    @@ -346,13 +346,14 @@ irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node)

    mutex_lock(&sparse_irq_lock);

    - start = bitmap_find_next_zero_area(allocated_irqs, nr_irqs, from, cnt, 0);
    + start = bitmap_find_next_zero_area(allocated_irqs, IRQ_BITMAP_BITS,
    + from, cnt, 0);
    ret = -EEXIST;
    if (irq >=0 && start != irq)
    goto err;

    - if (start >= nr_irqs) {
    - ret = irq_expand_nr_irqs(cnt);
    + if (start + cnt > nr_irqs) {
    + ret = irq_expand_nr_irqs(start + cnt);
    if (ret)
    goto err;
    }

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