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

[Darren Hart]

Josh Stone wrote:
> On 05/20/2009 02:44 AM, Kiran wrote:
>> BUG: scheduling while atomic: stapio/0x00000001/26142, CPU#3
>> [...]
>>  [<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]
> 
> enter_end_probe will call preempt_disable, and apparently the call path
> from cpufreq_unregister_notifier can sleep.  Is this true only of the RT
> kernel?

The call into the __synchronize_sched() from synchronize_rcu() appears 
to be able to sleep regardless of -rt.  It's possible -rt is more likely 
to make them sleep.


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