BUG: [preempt-rt] scheduling while atomic: stapio

[Darren Hart]

Jim Keniston wrote:
> On Wed, 2009-05-20 at 15:14 +0530, Kiran wrote:
>> Hi,

Hi Josh,

Sorry for the delay in responding, I'm on paternity leave right now, so 
I'm experiencing high email response latency ;-)

>>
>> I am getting the following bug report in dmesg when I run pfaults.stp

I presume that is a page fault tapset of some sort?

>> script in the systemtap.examples/memory. I am using systemtap-0.9.7 and
>> kernel version is 2.6.29-rt4.
> 
> The first thing that comes to mind is that spinlocks are different in
> (at least some) real-time kernels.  They can give up and sleep after a
> while.  If you want spinlocks that are guaranteed not to sleep, you have
> to use the raw_* versions of the spinlock functions.

Just the declaration actually, the functions are the same.

--
Darren

> That's about the
> extent of my (mis)information on the subject.  I'm cc-ing an RT guy
> (Darren) in case he can help.
> 
> Jim Keniston
> 
>> BUG: scheduling while atomic: stapio/0x00000001/26142, CPU#3
>> Modules linked in: stap_246f93f30a500769142af9987624737a_5072 ipv6 
>> autofs4 i2c_dev i2c_core hidp rfcomm l2cap bluetooth sunrpc dm_mirror 
>> dm_region_hash dm_log dm_multipath scsi_dh dm_mod video output sbs 
>> sbshc battery ac parport_pc lp parport sg bnx2 serio_raw button shpchp 
>> k8temp hwmon pcspkr mptsas mptscsih scsi_transport_sas mptbase sd_mod 
>> scsi_mod ext3 jbd mbcache uhci_hcd ohci_hcd ehci_hcd [last unloaded: 
>> stap_8455b451d15976a5e16919831aef7e51_3974]
>> Pid: 26142, comm: stapio Not tainted 2.6.29.1-rt4 #1
>> Call Trace:
>>  [<ffffffff81040341>] __schedule_bug+0x6f/0x8a
>>  [<ffffffff8136f748>] __schedule+0x9f/0x94a
>>  [<ffffffff81370433>] schedule+0x1d/0x46
>>  [<ffffffff81370597>] schedule_timeout+0x37/0x1a9
>>  [<ffffffff810415a9>] ? check_preempt_wakeup+0x138/0x16e
>>  [<ffffffff8136f3f2>] wait_for_common+0xcb/0x159
>>  [<ffffffff81043694>] ? default_wake_function+0x0/0x38
>>  [<ffffffff8136f5b9>] wait_for_completion+0x2b/0x41
>>  [<ffffffff8109cbc9>] __synchronize_sched+0x57/0x72
>>  [<ffffffff8105f335>] ? wakeme_after_rcu+0x0/0x36
>>  [<ffffffff81067016>] ? srcu_readers_active_idx+0x5e/0x89
>>  [<ffffffff810670b0>] synchronize_srcu+0x6f/0x96
>>  [<ffffffff8106787d>] srcu_notifier_chain_unregister+0x60/0x82
>>  [<ffffffff812a2dea>] cpufreq_unregister_notifier+0x35/0x5c
>>  [<ffffffffa02e0a1f>] _stp_kill_time+0xb6/0xbd [stap_246f93f30a500769142af9987624737a_5072]
>>  [<ffffffffa02e1749>] probe_1391+0x3c/0xa8 [stap_246f93f30a500769142af9987624737a_5072]
>>  [<ffffffffa02e2621>] enter_end_probe+0x14a/0x1e3 [stap_246f93f30a500769142af9987624737a_5072]
>>  [<ffffffffa02e2ed1>] _stp_cleanup_and_exit+0x2df/0x2f8 [stap_246f93f30a500769142af9987624737a_5072]
>>  [<ffffffffa02e51df>] _stp_ctl_write_cmd+0x460/0x7f8 [stap_246f93f30a500769142af9987624737a_5072]
>>  [<ffffffff81044e0b>] ? __wake_up+0x4d/0x6e 
>>  [<ffffffff81229bca>] ? tty_ldisc_deref+0x74/0x8f
>>  [<ffffffff81169d20>] ? security_file_permission+0x24/0x3a
>>  [<ffffffff810f00f7>] vfs_write+0xc1/0x180
>>  [<ffffffff810f07c3>] sys_write+0x56/0x93
>>  [<ffffffff8100beeb>] system_call_fastpath+0x16/0x1b
>>
>> Could someone please provide pointers on the cause of this bug?
>>
>>
>>
> 


-- 
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team