Re: Problems with hard irq? (inconsistent lock state)

On Wed, Oct 04, 2006 at 07:43:08AM +0200, Jarek Poplawski wrote:
On 29-09-2006 13:45, Axel C. Voigt wrote:

Hello all,

today I received the following stack backtrace using debian-2.6.18 with our communications driver accessing a ACM device. This happened when removing (powering off and/or on) the mobile phone (nokia 6630) at /dev/ttyACMx

Are someone able to get a hint for me?

--schnipp--
Sep 29 13:29:53 mcs70 kernel:
Sep 29 13:29:53 mcs70 kernel: =================================
Sep 29 13:29:53 mcs70 kernel: [ INFO: inconsistent lock state ]
Sep 29 13:29:53 mcs70 kernel: ---------------------------------
Sep 29 13:29:53 mcs70 kernel: inconsistent {hardirq-on-W} -> {in-hardirq-W} usage.
Sep 29 13:29:53 mcs70 kernel: startDV24/3864 [HC1[1]:SC0[0]:HE0:SE1] takes:
Sep 29 13:29:53 mcs70 kernel: (&acm->read_lock){++..}, at: [<e08952d8>] acm_read_bulk+0x60/0xde [cdc_acm]
Sep 29 13:29:53 mcs70 kernel: {hardirq-on-W} state was registered at:
Sep 29 13:29:53 mcs70 kernel: [<c01321f3>] lock_acquire+0x56/0x73
Sep 29 13:29:53 mcs70 kernel: [<c02ce42a>] _spin_lock+0x1a/0x25
Sep 29 13:29:53 mcs70 kernel: [<e08953a8>] acm_rx_tasklet+0x52/0x2be [cdc_acm]
Sep 29 13:29:53 mcs70 kernel: [<c011f868>] tasklet_action+0x6d/0xd7
Sep 29 13:29:53 mcs70 kernel: [<c011f526>] __do_softirq+0x79/0xf2
...
Sep 29 13:29:53 mcs70 kernel: stack backtrace:
Sep 29 13:29:53 mcs70 kernel: [<c010376e>] show_trace+0x16/0x18
Sep 29 13:29:53 mcs70 kernel: [<c010383c>] dump_stack+0x19/0x1b
Sep 29 13:29:53 mcs70 kernel: [<c0130ad8>] print_usage_bug+0x1e1/0x1eb
Sep 29 13:29:53 mcs70 kernel: [<c0130b86>] mark_lock+0xa4/0x4d9
Sep 29 13:29:53 mcs70 kernel: [<c0131823>] __lock_acquire+0x41a/0x841
Sep 29 13:29:53 mcs70 kernel: [<c01321f3>] lock_acquire+0x56/0x73
Sep 29 13:29:53 mcs70 kernel: [<c02ce42a>] _spin_lock+0x1a/0x25
Sep 29 13:29:53 mcs70 kernel: [<e08952d8>] acm_read_bulk+0x60/0xde [cdc_acm]
...
Sep 29 13:29:53 mcs70 kernel: [<c0104b26>] do_IRQ+0x4e/0x5f
Sep 29 13:29:53 mcs70 kernel: [<c0103339>] common_interrupt+0x25/0x2c
...

It looks in drivers/usb/class/cdc-acm.c acm_rx_tasklet could be preempted
with acm->read_lock by acm_read_bulk which uses the same lock from hardirq
context.

So probably spin_lock_irqsave is needed.

Yup. Care to send a patch?

thanks,

greg k-h
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