Re: Problems with 2.6.17-rt8

["Robert Crocombe" <rcrocomb@gmail.com>]

I am sad.

Okay, I couldn't use that same machine, which had to be swapped with
something else,  but I have a very similar machine (32GB vs 8GB of
RAM, 1 additional video card and some extra 1394b cards) which hit the
same problem.  The trace from it is:

md0_raid1/1118[CPU#3]: BUG in debug_rt_mutex_unlock at
kernel/rtmutex-debug.c:471

Call Trace:
       <ffffffff80487453>{_raw_spin_lock_irqsave+34}
       <ffffffff8022cc03>{__WARN_ON+105}
       <ffffffff8022cbbe>{__WARN_ON+36}
       <ffffffff8024880b>{debug_rt_mutex_unlock+204}
       <ffffffff80486621>{rt_lock_slowunlock+30}
       <ffffffff80487196>{__lock_text_start+14}
       <ffffffff802792f9>{kmem_cache_alloc+207}
       <ffffffff8025b394>{mempool_alloc_slab+22}
       <ffffffff8025b783>{mempool_alloc+80}
       <ffffffff80248e35>{constant_test_bit+9}
       <ffffffff80487960>{_raw_spin_unlock+51}
       <ffffffff80486649>{rt_lock_slowunlock+70}
       <ffffffff802fde74>{get_request+375}
       <ffffffff80209a6d>{mcount+45}
       <ffffffff802fe04c>{get_request_wait+45}
       <ffffffff80209a6d>{mcount+45}
       <ffffffff803023c5>{as_merge+0}
       <ffffffff803023db>{as_merge+22}
       <ffffffff802fe425>{__make_request+750}
       <ffffffff803fc2b7>{md_thread+0}
       <ffffffff802fba78>{generic_make_request+380}
       <ffffffff80248e35>{constant_test_bit+9}
       <ffffffff80487960>{_raw_spin_unlock+51}
       <ffffffff803fc2b7>{md_thread+0}
       <ffffffff803ea43c>{raid1d+246}
       <ffffffff80209a6d>{mcount+45}
       <ffffffff80209a6d>{mcount+45}
       <ffffffff80486649>{rt_lock_slowunlock+70}
       <ffffffff80485568>{thread_return+230}
       <ffffffff80485568>{thread_return+230}
       <ffffffff80248e35>{constant_test_bit+9}
       <ffffffff80487960>{_raw_spin_unlock+51}
       <ffffffff80486649>{rt_lock_slowunlock+70}
       <ffffffff80485568>{thread_return+230}
       <ffffffff80487196>{__lock_text_start+14}
       <ffffffff803fc2b7>{md_thread+0}
       <ffffffff8023fb55>{keventd_create_kthread+0}
       <ffffffff803fc3cf>{md_thread+280}
       <ffffffff8023ff97>{autoremove_wake_function+0}
       <ffffffff8023fe5a>{kthread+224}
       <ffffffff802273bf>{schedule_tail+198}
       <ffffffff8020ae12>{child_rip+8}
       <ffffffff8023fb55>{keventd_create_kthread+0}
       <ffffffff80485568>{thread_return+230}
       <ffffffff80485568>{thread_return+230}
       <ffffffff80485568>{thread_return+230}
       <ffffffff8023fd7a>{kthread+0}
       <ffffffff8020ae0a>{child_rip+0}
---------------------------
| preempt count: 00000002 ]
| 2-level deep critical section nesting:
----------------------------------------
.. [<ffffffff8048736f>] .... _raw_spin_lock+0x1b/0x28
.....[<ffffffff80486619>] ..   ( <= rt_lock_slowunlock+0x16/0x70)
.. [<ffffffff80487453>] .... _raw_spin_lock_irqsave+0x22/0x33
.....[<ffffffff8022cbbe>] ..   ( <= __WARN_ON+0x24/0x8a)

which makes:

   <ffffffff802792f9>{kmem_cache_alloc+207}

the interesting part?

However:

rcrocomb@spanky:2.6.17-rt8$ grep DEBUG_INFO .config
CONFIG_DEBUG_INFO=y
rcrocomb@spanky:2.6.17-rt8$ cd arch/x86_64/boot/compressed/
rcrocomb@spanky:compressed$ gdb vmlinux
GNU gdb Red Hat Linux (6.3.0.0-1.122rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu"...
(no debugging symbols found)
Using host libthread_db library "/lib64/libthread_db.so.1".

(gdb) li *0xffffffff802792f9
No symbol table is loaded.  Use the "file" command.

Huh.

-- 
Robert Crocombe
rcrocomb@gmail.com

In case this might be useful:

rcrocomb@spanky:2.6.17-rt8$ grep -i debug .config
.
.
.
CONFIG_DEBUG_KERNEL=y
# CONFIG_DEBUG_SLAB is not set
CONFIG_DEBUG_PREEMPT=y
CONFIG_DEBUG_RT_MUTEXES=y
CONFIG_DEBUG_PI_LIST=y
CONFIG_DEBUG_TRACE_IRQFLAGS=y
# CONFIG_DEBUG_KOBJECT is not set
CONFIG_DEBUG_INFO=y
# CONFIG_DEBUG_FS is not set
# CONFIG_DEBUG_VM is not set
CONFIG_DEBUG_RODATA=y
CONFIG_IOMMU_DEBUG=y