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    Subject[patch] Fix deadlock in pcmcia as found by lockdep
    On Thu, 2006-06-29 at 23:18 -0700, Miles Lane wrote:
    > To trigger this, I booted with a U.S. Robotics USR2210 Wifi card
    > plugged into my cardbus slot. I then ran "pccardctl eject" and then
    > removed and then reinserted the card. After looking at the latest
    > PCMCIA info, it seems that I may need to add some kernel boot options
    > to work around a BIOS or other problem that causes trouble when
    > removing a card.
    > PM: Removing info for pci:0000:02:00.0
    > PCMCIA: socket c1ebc9e0: *** DANGER *** unable to remove socket power

    ok this looks like a real bug:

    void pcmcia_parse_events(struct pcmcia_socket *s, u_int events)
    cs_dbg(s, 4, "parse_events: events %08x\n", events);
    if (s->thread) {
    s->thread_events |= events;

    } /* pcmcia_parse_events */

    that function gets called from both user context and irq context!

    user context:
    [<c1181270>] pcmcia_parse_events+0x3e/0x6b
    [<c1181945>] pcmcia_register_socket+0x29b/0x2fc
    [<c118a8d1>] yenta_probe+0x51b/0x55c
    [<c110d537>] pci_device_probe+0x39/0x5b

    eg in pcmcia_register_socket:

    ret = kernel_thread(pccardd, socket, CLONE_KERNEL);
    if (ret < 0)
    goto err;

    if(!socket->thread) {
    printk(KERN_WARNING "PCMCIA: warning: socket thread for
    socket %p did not start\n", socket);
    return -EIO;
    pcmcia_parse_events(socket, SS_DETECT);

    clearly sleeping/user context

    interrupt context:
    yenta_interrupt calls pcmcia_parse_events like this:
    if (events)
    pcmcia_parse_events(&socket->socket, events);

    return IRQ_HANDLED;

    and that's the irq handler.

    Dominik: this really wants to have _irqsave versions of the spinlock
    like this:

    the PCMCIA layer calls pcmcia_parse_events both from user context and
    IRQ context; the lock thus needs to be irqsave to avoid deadlocks

    Signed-off-by: Arjan van de Ven <>

    drivers/pcmcia/cs.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    Index: linux-2.6.17-mm4/drivers/pcmcia/cs.c
    --- linux-2.6.17-mm4.orig/drivers/pcmcia/cs.c
    +++ linux-2.6.17-mm4/drivers/pcmcia/cs.c
    @@ -697,11 +697,12 @@ static int pccardd(void *__skt)
    void pcmcia_parse_events(struct pcmcia_socket *s, u_int events)
    + unsigned long flags;
    cs_dbg(s, 4, "parse_events: events %08x\n", events);
    if (s->thread) {
    - spin_lock(&s->thread_lock);
    + spin_lock_irqsave(&s->thread_lock, flags);
    s->thread_events |= events;
    - spin_unlock(&s->thread_lock);
    + spin_unlock_irqrestore(&s->thread_lock, flags);

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      Last update: 2006-06-30 10:33    [W:0.024 / U:54.700 seconds]
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