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    SubjectRe: PATCH] net: b44.c fix sleeping-with-spinlock-helt during resume
    Date
    On Sunday 01 June 2008 05:11:30 Arjan van de Ven wrote:
    > From: Arjan van de Ven <arjan@linux.intel.com>
    > Subject: [PATCH] net: b44.c fix sleeping-with-spinlock-helt during resume
    > CC: Michael Buesch <mb@bu3sch.de>
    >
    > The b44.c driver calls b44_chip_reset() from the resume path,
    > with the device spinlock held.
    > Unfortunately, b44_chip_reset() calls ssb_pcicore_dev_irqvecs_enable()
    > which is a sleeping function (and calls might_sleep), if and only if
    > the device hasn't been enabled yet.
    >
    > Not having this hardware, the safest solution seems to be to enable
    > the irqvec before taking the spinlock...
    >
    > http://www.kerneloops.org/search.php?search=ssb_pcicore_dev_irqvecs_enable
    >
    > Reported-by: www.kerneloops.org
    > Signed-off-by: Arjan van de Ven
    > ---
    > drivers/net/b44.c | 12 ++++++++++--
    > 1 files changed, 10 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/net/b44.c b/drivers/net/b44.c
    > index 59dce6a..6028129 100644
    > --- a/drivers/net/b44.c
    > +++ b/drivers/net/b44.c
    > @@ -1278,6 +1278,7 @@ static void b44_chip_reset(struct b44 *bp, int reset_kind)
    > bw32(bp, B44_DMARX_CTRL, 0);
    > bp->rx_prod = bp->rx_cons = 0;
    > } else
    > + /* this function sleeps! */
    > ssb_pcicore_dev_irqvecs_enable(&sdev->bus->pcicore, sdev);
    >
    > ssb_device_enable(bp->sdev, 0);
    > @@ -1374,7 +1375,7 @@ static int b44_set_mac_addr(struct net_device *dev, void *p)
    > }
    >
    > /* Called at device open time to get the chip ready for
    > - * packet processing. Invoked with bp->lock held.
    > + * packet processing. Sometimes invoked with bp->lock held.
    > */
    > static void __b44_set_rx_mode(struct net_device *);
    > static void b44_init_hw(struct b44 *bp, int reset_kind)
    > @@ -2288,6 +2289,13 @@ static int b44_resume(struct ssb_device *sdev)
    > return rc;
    > }
    >
    > + /*
    > + * If the device isn't enabled yet, we need to do so before taking
    > + * the spinlock, since the enablinging function sleeps.
    > + */
    > + if (!ssb_device_is_enabled(bp->sdev))
    > + ssb_pcicore_dev_irqvecs_enable(&sdev->bus->pcicore, sdev);
    > +
    > spin_lock_irq(&bp->lock);
    >
    > b44_init_rings(bp);

    I'm not sure how this is supposed to fix the bug.
    I think you will call ssb_pcicore_dev_irqvecs_enable() twice this way.
    The call in b44_chip_reset() will still trigger.

    Besides that, this only is a theoretical issue, as the function does
    only sleep on a PCI-E device. But as b44 PCI-E devices don't exist,
    it will never sleep. So I'd rather replace the might_sleep() with a
    might_sleep_if() call.
    Something like the following:

    Index: wireless-testing/drivers/ssb/driver_pcicore.c
    ===================================================================
    --- wireless-testing.orig/drivers/ssb/driver_pcicore.c 2008-04-23 16:06:56.000000000 +0200
    +++ wireless-testing/drivers/ssb/driver_pcicore.c 2008-06-01 12:02:33.000000000 +0200
    @@ -537,12 +537,12 @@ int ssb_pcicore_dev_irqvecs_enable(struc
    int err = 0;
    u32 tmp;

    - might_sleep();
    -
    if (!pdev)
    goto out;
    bus = pdev->bus;

    + might_sleep_if(pdev->id.coreid != SSB_DEV_PCI);
    +
    /* Enable interrupts for this device. */
    if (bus->host_pci &&
    ((pdev->id.revision >= 6) || (pdev->id.coreid == SSB_DEV_PCIE))) {


    --
    Greetings Michael.


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