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    SubjectRe: [PATCH/RFC] remove irqs_disabled warning from local_bh_enable
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    On Friday 20 June 2008 18:01:09 Michael Buesch wrote:
    > On Friday 20 June 2008 17:55:41 Ingo Molnar wrote:
    > >
    > > * Michael Buesch <mb@bu3sch.de> wrote:
    > >
    > > > On Friday 20 June 2008 17:27:48 Ingo Molnar wrote:
    > > > > [<c012b361>] local_bh_enable_ip+0xd1/0xe0
    > > > > [<c08d9f9f>] _spin_unlock_bh+0x2f/0x40
    > > > > [<c0471b92>] vortex_timer+0xe2/0x3e0
    > > >
    > > > > real bug or false positive?
    > > >
    > > > Well, a timer runs with IRQs disabled, no? So this would be a bug.
    > >
    > > indeed - agreed :) [no time for me to fix it, but can test any rfc patch.]
    >
    > A quick workaround always is to convert the lock into an _irqsafe lock.
    > Although it introduces higher overhead (interrupt-wise), it prevents the bug.
    > A real fix would require to understand the locking in the driver, which I
    > don't, as I never looked at the driver. :)


    However, looking at the driver I think the fix actually is trivial:

    Index: wireless-testing/drivers/net/3c59x.c
    ===================================================================
    --- wireless-testing.orig/drivers/net/3c59x.c 2008-05-16 00:26:29.000000000 +0200
    +++ wireless-testing/drivers/net/3c59x.c 2008-06-20 18:16:55.000000000 +0200
    @@ -1768,9 +1768,10 @@ vortex_timer(unsigned long data)
    case XCVR_MII: case XCVR_NWAY:
    {
    ok = 1;
    - spin_lock_bh(&vp->lock);
    + /* Interrupts are already disabled */
    + spin_lock(&vp->lock);
    vortex_check_media(dev, 0);
    - spin_unlock_bh(&vp->lock);
    + spin_unlock(&vp->lock);
    }
    break;
    default: /* Other media types handled by Tx timeouts. */

    vp->lock is also taken in hardware IRQ context, so we _have_ to always
    use irqsafe locking. As we run in a timer with IRQs disabled,
    we can simply use spin_lock.

    --
    Greetings Michael.


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