Hi,
I am trying to get a linux kernel running on a mips processor with the
realtime-preempt patches applied (2.6.15-rt21). I have gotten it
running, but it is quite unstable and frequently hangs. I have
tracked down one occurrence as a deadlock. This one in particular
occurs when I send a break (eg: reBoot) via the serial console.
I have deadlock detection turned on, and got some output from it.
Please find it at the end of this message.
I believe it is caused by an attempt to lock the same spinlock twice
on one thread as follows (calls ordered from bottom to top):
drivers/serial/8250.c: serial8250_console_write <== Tries
to lock up->port.lock
kernel/printk.c: __call_console_drivers
kernel/printk.c: _call_console_drivers
kernel/printk.c: call_console_drivers
kernel/printk.c: release_console_sem
kernel/printk.c: vprintk
kernel/printk.c: printk
drivers/char/sysrq.c: __handle_sysrq
drivers/char/sysrq.c: handle_sysrq
include/linux/serial_core.h: uart_handle_sysrq_char
drivers/serial/8250.c: receive_chars
drivers/serial/8250.c: serial8250_handle_port
drivers/serial/8250.c: serial8250_interrupt <== locks
up->port.lock prior to calling serial8250_handle_port
...
I am uncertain how to fix this problem. Any assistance that could be
provided would be appreciated. Please cc any response to me as I am
not subscribed to news groups. Thanks.
Ryan McAvoy
==========================================
[ BUG: lock recursion deadlock detected! |
------------------------------------------
already locked: [8033304c] {&port->lock}
.. ->owner: 811a6e82
.. held by: IRQ 27: 105 [811a6e80, 56]
... acquired at: -{current task's backtrace}----------------->
Call Trace:
[<80147d58>] check_deadlock+0x280/0x308
[<80147d3c>] check_deadlock+0x264/0x308
[<8012666c>] vprintk+0x324/0x3f8
[<8011f24c>] activate_task+0x94/0xc8
[<801f8b2c>] serial8250_console_write+0x7c/0x7b0
[<80146124>] task_blocks_on_lock+0x3c/0x238
[<8011fc80>] try_to_wake_up+0xa0/0x1f0
[<8029b3e8>] ___down_mutex+0x310/0x5c0
[<8011f24c>] activate_task+0x94/0xc8
[<801f8b2c>] serial8250_console_write+0x7c/0x7b0
[<80125ae0>] __call_console_drivers+0x80/0xb0
[<80126108>] release_console_sem+0x128/0x368
[<8012666c>] vprintk+0x324/0x3f8
[<80126598>] vprintk+0x250/0x3f8
[<8029b1f4>] ___down_mutex+0x11c/0x5c0
[<8012675c>] printk+0x1c/0x28
[<801f2158>] __handle_sysrq+0x68/0x178
[<802f7000>] _sinittext+0x0/0x80
[<801f66ac>] receive_chars+0x1ec/0x338
[<80146390>] ____up_mutex+0x70/0x218
[<801f6be8>] serial8250_interrupt+0x248/0x268
[<80299ca0>] schedule+0x68/0x168
[<80299830>] __schedule+0x5c8/0x9d0
[<8014e4ec>] handle_IRQ_event+0xa4/0x1a8
[<8014e5f8>] handle_simple_irq+0x0/0x138
[<80299ca0>] schedule+0x68/0x168
[<8014e5f8>] handle_simple_irq+0x0/0x138
[<8014e730>] handle_level_irq+0x0/0x160
[<8014f8c0>] do_irqd+0x160/0x378
[<8014f760>] do_irqd+0x0/0x378
[<80141058>] kthread+0x130/0x178
[<80104030>] kernel_thread_helper+0x10/0x18
[<80104020>] kernel_thread_helper+0x0/0x18
showing all tasks:
? init: 1 [80a73730, 116] (not blocked)
S IRQ 6: 2 [80a73298, 50] (not blocked)
S IRQ 21: 3 [80a72e00, 51] (not blocked)
S softirq-high/0: 4 [80a72968, 98] (not blocked)
S softirq-timer/0: 5 [80a724d0, 98] (not blocked)
S softirq-net-tx/: 6 [80a72038, 98] (not blocked)
S softirq-net-rx/: 7 [87f89750, 98] (not blocked)
S softirq-scsi/0: 8 [87f892b8, 98] (not blocked)
S softirq-tasklet: 9 [87f88e20, 98] (not blocked)
S watchdog/0: 10 [87f88988, 0] (not blocked)
S desched/0: 11 [87f884f0, 105] (not blocked)
S events/0: 12 [87f88058, 98] (not blocked)
S khelper: 13 [87fb1770, 110] (not blocked)
S kthread: 14 [87fb12d8, 110] (not blocked)
S IRQ 8: 15 [87fb0e40, 52] (not blocked)
S IRQ 9: 16 [87fb09a8, 53] (not blocked)
S kblockd/0: 17 [87fb0510, 120] (not blocked)
S IRQ 28: 19 [8118d790, 54] (not blocked)
S pdflush: 38 [8118c9c8, 125] (not blocked)
S pdflush: 39 [8118d2f8, 115] (not blocked)
S aio/0: 41 [87fb0078, 120] (not blocked)
S kswapd0: 40 [811a77b0, 125] (not blocked)
S mtdblockd: 76 [8118ce60, 115] (not blocked)
S IRQ 2: 104 [8118c098, 55] (not blocked)
D IRQ 27: 105 [811a6e80, 56] (not blocked)
S udevd: 121 [811a69e8, 111] (not blocked)
S klogd: 399 [87d03338, 125] (not blocked)
S syslogd: 402 [87d02a08, 116] (not blocked)
S thttpd: 413 [811a60b8, 116] (not blocked)
S sh: 421 [8118c530, 115] (not blocked)
=============================================
[ turning off deadlock detection.Please report this trace. ]
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