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    Subject[PATCH] fsl_usb2_udc: fix recursive lock
    Date
    UDC needs to release lock before calling out to gadget driver, since
    it may need to reenter. The change fixes kernel BUG observed on rt
    kernel.

    > kernel BUG at kernel/rtmutex.c:683!
    > stopped custom tracer.
    > Oops: Exception in kernel mode, sig: 5 [#1]
    > PREEMPT MPC834x ITX
    > NIP: c021629c LR: c0216270 CTR: 00000000
    > REGS: df761d70 TRAP: 0700 Not tainted (2.6.23.9-rt13)
    > MSR: 00021032 <ME,IR,DR> CR: 28000022 XER: 00000000
    > TASK = df632080[241] 'IRQ-38' THREAD: df760000
    > GPR00: 00000001 df761e20 df632080 00000000 11111111 00000000 df761e6c
    > 00000000
    > GPR08: df761e48 00000000 df761e50 00000000 80000000 ede5cdde 1fffd000
    > 00800000
    > GPR16: ffffffff 00000000 007fff00 00000040 00000000 007ffeb0 00000000
    > 1fff8b08
    > GPR24: 00000000 00000026 00000000 df79a320 c026b2e8 c02240bc 00009032
    > df79a320
    > NIP [c021629c] rt_spin_lock_slowlock+0x9c/0x200
    > LR [c0216270] rt_spin_lock_slowlock+0x70/0x200
    > Call Trace:
    > [df761e20] [c0216270] rt_spin_lock_slowlock+0x70/0x200 (unreliable)
    > [df761e90] [c0182828] fsl_ep_disable+0xcc/0x154
    > [df761eb0] [c0184d30] eth_reset_config+0x88/0x1d0
    > [df761ed0] [c0184ec0] eth_disconnect+0x48/0x64
    > [df761ef0] [c01831a4] reset_queues+0x60/0x78
    > [df761f00] [c0183b74] fsl_udc_irq+0x9b8/0xa58
    > [df761f50] [c003ef30] handle_IRQ_event+0x64/0x100
    > [df761f80] [c003f758] thread_simple_irq+0x6c/0xc8
    > [df761fa0] [c003f888] do_irqd+0xd4/0x2e4
    > [df761fd0] [c0032284] kthread+0x50/0x8c
    > [df761ff0] [c000f9b4] kernel_thread+0x44/0x60

    Signed-off-by: Li Yang <leoli@freescale.com>
    Cc: Eugene T. Bordenkircher <Eugene_Bordenkircher@selinc.com>
    Cc: David Brownell <david-b@pacbell.net>
    ---
    drivers/usb/gadget/fsl_usb2_udc.c | 2 ++
    1 files changed, 2 insertions(+), 0 deletions(-)

    diff --git a/drivers/usb/gadget/fsl_usb2_udc.c b/drivers/usb/gadget/fsl_usb2_udc.c
    index 651b827..1868754 100644
    --- a/drivers/usb/gadget/fsl_usb2_udc.c
    +++ b/drivers/usb/gadget/fsl_usb2_udc.c
    @@ -1627,7 +1627,9 @@ static int reset_queues(struct fsl_udc *udc)
    udc_reset_ep_queue(udc, pipe);

    /* report disconnect; the driver is already quiesced */
    + spin_unlock(&udc->lock);
    udc->driver->disconnect(&udc->gadget);
    + spin_lock(&udc->lock);

    return 0;
    }
    --
    1.5.5.1.248.g4b17


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