Real-Time Preemption: BUG initializing kgdb

["kus Kusche Klaus" <kus@keba.com>]

I tried to merge the kgdb and the rt patches (not too difficult, only
three rejects, and they all look trivial). The resulting kernel
compiles, boots, and works fine.

However, kgdb initialization generates a BUG, and kgdb does not work at
all (gdb on the host is unable to connect to the target, and Alt-SysRq-g
has no effect).

The bug:

May 10 15:56:46 OF455 kern.notice kernel: Linux version
2.6.12-rc3-RT-V0.7.46-02 (kk@silver) (gcc version 3.4.3) #3 Tue May 10
13:41:59 CEST 2005

 ...

May 10 15:56:46 OF455 kern.warn kernel: kgdb <20030915.1651.33> : port
=2e8, IRQ=5, divisor =1
May 10 15:56:46 OF455 kern.err kernel: BUG: scheduling while atomic:
swapper/0x00000001/1
May 10 15:56:46 OF455 kern.warn kernel: caller is schedule+0x102/0x110
May 10 15:56:46 OF455 kern.warn kernel:  [<c0102f29>]
dump_stack+0x17/0x19 (12)
May 10 15:56:46 OF455 kern.warn kernel:  [<c025de85>]
__schedule+0xa5/0x633 (88)
May 10 15:56:46 OF455 kern.warn kernel:  [<c025e515>]
schedule+0x102/0x110 (36)
May 10 15:56:46 OF455 kern.warn kernel:  [<c025e671>]
wait_for_completion+0x86/0xbd (84)
May 10 15:56:46 OF455 kern.warn kernel:  [<c01262eb>]
kthread_create+0x118/0x146 (208)
May 10 15:56:46 OF455 kern.warn kernel:  [<c012be97>]
start_irq_thread+0x42/0x77 (32)
May 10 15:56:46 OF455 kern.warn kernel:  [<c012ba57>]
setup_irq+0x51/0x12f (28)
May 10 15:56:46 OF455 kern.warn kernel:  [<c012bc9e>]
request_irq+0x86/0x9f (24)
May 10 15:56:46 OF455 kern.warn kernel:  [<c01a0b73>]
kgdb_enable_ints_now+0x76/0xae (16)
May 10 15:56:46 OF455 kern.warn kernel:  [<c02d26e7>]
kgdb_enable_ints+0x38/0x3f (8)
May 10 15:56:46 OF455 kern.warn kernel:  [<c02c47ff>]
do_initcalls+0x62/0xb3 (32)
May 10 15:56:46 OF455 kern.warn kernel:  [<c02c4871>]
do_basic_setup+0x21/0x23 (8)
May 10 15:56:46 OF455 kern.warn kernel:  [<c01002cd>] init+0x32/0xfd
(20)
May 10 15:56:46 OF455 kern.warn kernel:  [<c0100c21>]
kernel_thread_helper+0x5/0xb (1055084564)

 ...

This is with RT-V0.7.46-02 and the kgdb patchset from -rc3-mm3.

Any hints or suggestions?

-- 
Klaus Kusche                 (Software Development - Control Systems)
KEBA AG             Gewerbepark Urfahr, A-4041 Linz, Austria (Europe)
Tel: +43 / 732 / 7090-3120                 Fax: +43 / 732 / 7090-6301
E-Mail: kus@keba.com                                WWW: www.keba.com
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