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    SubjectRe: [PATCH] Fix USB suspend/resume crasher
    Date
    On Thursday, 24 of November 2005 22:01, Benjamin Herrenschmidt wrote:
    >
    > >
    > > Well, it's there (actually the problem occurs in vanilla 2.6.15-rc2-mm1 that
    > > contains the patch). Do you mean it should go before the
    > >
    > > if (readl(&ehci->regs->configured_flag) != FLAG_CF)
    > > goto restart;
    > >
    > > thing?
    >
    > Yes.
    >
    > > > It may be worth following it with a memory barrier actually... just in case
    > > > (due to the absence of locks in that area).
    > >
    > > wmb()?
    >
    > Yup.
    >
    > I wrote that patch against a tree that had different things in that
    > function, Greg merged it by hand but he got that little bit wrong
    > unfortunately. I'll send a new patch later today.

    Thanks.

    FWIW, does the appended change look reasonable to you? (It apparently
    helps. ;-))

    Rafael


    Index: linux-2.6.15-rc2-mm1/drivers/usb/host/ehci-pci.c
    ===================================================================
    --- linux-2.6.15-rc2-mm1.orig/drivers/usb/host/ehci-pci.c 2005-11-24 21:42:34.000000000 +0100
    +++ linux-2.6.15-rc2-mm1/drivers/usb/host/ehci-pci.c 2005-11-24 21:50:38.000000000 +0100
    @@ -281,12 +281,13 @@
    if (time_before(jiffies, ehci->next_statechange))
    msleep(100);

    + set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
    + wmb();
    +
    /* If CF is clear, we lost PCI Vaux power and need to restart. */
    if (readl(&ehci->regs->configured_flag) != FLAG_CF)
    goto restart;

    - set_bit(HCD_FLAG_HW_ACCESSIBLE, &hcd->flags);
    -
    /* If any port is suspended (or owned by the companion),
    * we know we can/must resume the HC (and mustn't reset it).
    * We just defer that to the root hub code.
    -
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