Hey Steven
This is the first time I try frace on this kernel. it turned out that
when enabling
ftrace kernel oops whenever one loads a module - see bellow.
I debugged it a little and the null pointer is in trace_module_add_events
in the loop , the call pointer is NULL.
for_each_event(call, start, end) {
call is null.
}
I will continue debugging it a bit more.
4.137324] e100 0000:02:03.0: eth0: NIC Link is Up 100 Mbps Full Duplex
[ 5.180354] Disabling lock debugging due to kernel taint
[ 5.180792] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 5.180799] IP: [<c1084f7c>] trace_module_notify+0x9c/0x160
[ 5.180810] *pde = 00000000
[ 5.180813] Oops: 0000 [#1] PREEMPT
[ 5.180818] Modules linked in: sercos_driver(O+)
[ 5.180822]
[ 5.180826] Pid: 1079, comm: modprobe Tainted: G O
3.2.0-rc5-rt8 #8 N/A N/A /MODB
[ 5.180832] EIP: 0060:[<c1084f7c>] EFLAGS: 00010286 CPU: 0
[ 5.180836] EIP is at trace_module_notify+0x9c/0x160
[ 5.180839] EAX: de513f44 EBX: dfeecc60 ECX: de513e0c EDX: de513e74
[ 5.180842] ESI: 00000000 EDI: de513edc EBP: de60df3c ESP: de60df14
[ 5.180846] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
[ 5.180849] Process modprobe (pid: 1079, ti=de60c000 task=de519030
task.ti=de60c000)
[ 5.180852] Stack:
[ 5.180854] de513e74 de513f44 de513edc de513f44 de513e0c de513e74
7fbb1b30 c14578b0
[ 5.180859] 00000000 c14563a0 de60df58 c1055ba5 dfeecc60 00000001
c1455d50 00000001
[ 5.180865] dfeecc60 de60df78 c1055ee3 fffffffd 00000000 00000000
dfeecc60 0000223f
[ 5.180870] Call Trace:
[ 5.180878] [<c1055ba5>] notifier_call_chain+0x45/0x60
[ 5.180883] [<c1055ee3>] __blocking_notifier_call_chain+0x43/0x70
[ 5.180888] [<c1055f2f>] blocking_notifier_call_chain+0x1f/0x30
[ 5.180893] [<c1069682>] sys_init_module+0x62/0x1c0
[ 5.180900] [<c10c32c1>] ? sys_close+0x71/0xc0
[ 5.180906] [<c13441e1>] syscall_call+0x7/0xb
[ 5.180909] Code: 00 8d 90 44 01 00 00 83 c0 74 89 55 e4 89 45 ec
8d b4 26 00 00 00 00 8b 45 e4 8b 55 ec 89 7c 24 08 8b 4d e8 89 44 24
04 89 14 24
On Thu, Feb 2, 2012 at 4:12 PM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> On Thu, 2012-02-02 at 12:52 +0200, Raz wrote:
>> hey
>>
>> I am trying to understand why a user space MT process behaves in an
>> unexpected manner.
>> I have real time process, which executes most of its threads in RT priority,
>> and from time to time a task ( medium priority ) is executing without
>> trying to stop.
>>
>> There are times, that this task is hogging the entire process and no
>> other **higher*** rt priority
>> task is getting any cpu time.
>>
>> Linux is **not** getting hogged. when setting the serial console (
>> irq/serial ) and its shell ( /bin/sh )
>> to a higher priority linux is responsive.
>>
>> Observing the task list through ps command i can see that this task's
>> threads when
>> to un-interruptible sleep.
>>
>> Any idea why is it happening ?
>
> Some ideas, but I need a lot more information.
>
>> kernel is 3.2.0-rc5-rt8.
>
> Is this a x86 box?
>
> Can you run a trace on the task that is going berserk?
>
> Enable CONFIG_FUNCTION_TRACER in your kernel and do the following:
>
> # mount -t debugfs nodev /sys/kernel/debug
> # cd /sys/kernel/debug/tracing
> # echo <pid-of-berserk-task> > set_ftrace_pid
> # echo function > current_tracer
> # cat trace
>
> Thanks!
>
> -- Steve
>
>
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