Re: kernel 2.6 : cdc_acm problem

From: Benjamin Herrenschmidt (benh_at_kernel.crashing.org)
Date: 11/09/03

  • Next message: Ivan Kokshaysky: "Re: /dev/rtc on alpha"
    To: Colin Leroy <colin@colino.net>
    Date:	Sun, 09 Nov 2003 22:11:46 +1100
    
    

    On Sun, 2003-11-09 at 22:20, Colin Leroy wrote:
    > Hi,
    >
    > just to report a problem with kernel 2.6.0-tes9-benh.. Using my GPRS phone
    > to access internet spits out lots (real lots) of these to syslog:
    >
    > Nov 8 23:36:21 chloe kernel: Call trace:
    > Nov 8 23:36:21 chloe kernel: [c000b604] dump_stack+0x18/0x28
    > Nov 8 23:36:21 chloe kernel: [c000885c] check_bug_trap+0x84/0x98
    > Nov 8 23:36:21 chloe kernel: [c0008940] ProgramCheckException+0xd0/0x170
    > Nov 8 23:36:21 chloe kernel: [c0007ee0] ret_from_except_full+0x0/0x4c
    > Nov 8 23:36:21 chloe kernel: [c0021250] local_bh_enable+0x28/0x60
    > Nov 8 23:36:21 chloe kernel: [c0109c68] ppp_input+0x204/0x21c
    > Nov 8 23:36:21 chloe kernel: [c010e99c] ppp_async_input+0x50c/0x618
    > Nov 8 23:36:21 chloe kernel: [c010d890] ppp_asynctty_receive+0x50/0xac
    > Nov 8 23:36:21 chloe kernel: [c00d5c7c] flush_to_ldisc+0xa0/0xb0
    > Nov 8 23:36:21 chloe kernel: [c00d5d34] tty_flip_buffer_push+0x1c/0x3c
    > Nov 8 23:36:21 chloe kernel: [d98fb250] acm_read_bulk+0xdc/0x138
    > [cdc_acm]
    > Nov 8 23:36:21 chloe kernel: [c017e298] usb_hcd_giveback_urb+0x90/0xac
    > Nov 8 23:36:21 chloe kernel: [c0187ac8] finish_urb+0xd8/0xec
    > Nov 8 23:36:21 chloe kernel: [c0188f28] dl_done_list+0x7c/0x128
    > Nov 8 23:36:21 chloe kernel: [c0189a48] ohci_irq+0xec/0x1b4
    > Nov 8 23:36:21 chloe kernel: Badness in local_bh_enable at
    > kernel/softirq.c:121
    >
    > This makes the computer very irresponsive and the log-storm emptied the
    > battery in about 20 minutes :-)

    Looks like a bug calling local_bh_enable with irq off, though it isn't
    clear who is disabling them at this point. I don't have time to track
    it down more precisely right now, it could be either OHCI finishing the
    urbs within a spinlock_irqsave or some TTY or PPP issue, the ACM driver
    doesn't seem to play with irq masking by itself.

    Ben.
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