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    SubjectRe: Locking problem in usbserial with 2.6.23-git 5a34417f
    On Fri, 19 Oct 2007, Larry Finger wrote:

    > As I said earlier, the lock problem went away; however, I get the
    > following two kernel warnings:

    That's because I messed up the patch, sorry. The one below should work
    better.



    From: Jiri Kosina <jkosina@suse.cz>

    USB: usbserial - fix potential deadlock between write() and IRQ

    usb_serial_generic_write() doesn't disable interrupts when taking port->lock,
    and could therefore deadlock with usb_serial_generic_read_bulk_callback()
    being called from interrupt, taking the same lock. Fix it.

    Signed-off-by: Jiri Kosina <jkosina@suse.cz>

    diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c
    index 88a2c7d..9eb4a65 100644
    --- a/drivers/usb/serial/generic.c
    +++ b/drivers/usb/serial/generic.c
    @@ -208,14 +208,15 @@ int usb_serial_generic_write(struct usb_serial_port *port, const unsigned char *

    /* only do something if we have a bulk out endpoint */
    if (serial->num_bulk_out) {
    - spin_lock_bh(&port->lock);
    + unsigned long flags;
    + spin_lock_irqsave(&port->lock, flags);
    if (port->write_urb_busy) {
    - spin_unlock_bh(&port->lock);
    + spin_unlock_irqrestore(&port->lock, flags);
    dbg("%s - already writing", __FUNCTION__);
    return 0;
    }
    port->write_urb_busy = 1;
    - spin_unlock_bh(&port->lock);
    + spin_unlock_irqrestore(&port->lock, flags);

    count = (count > port->bulk_out_size) ? port->bulk_out_size : count;

    -
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