On 07/18/2012 01:41 PM, preeti wrote:
> On 07/18/2012 09:12 AM, Wanlong Gao wrote:
>> On 07/18/2012 11:41 AM, preeti wrote:
>>> On 07/18/2012 08:32 AM, Wanlong Gao wrote:
>>>> Hi Preeti,
>>>>
>>>>> Hi
>>>>>
>>>>> The test case included is a simple case for cpu hotplug.It does offlines
>>>>> the cpus that are online and does an online of the offlined cpus in a loop
>>>>>
>>>>> This stress test had failed on certain distros when the loop was run
>>>>> infinite times.This test is presented here for review of correctness and
>>>>> necessity,as this is the first attempt at contributing test cases to LTP
>>>>> from this end.
>>>>>
>>>>> The test is meant to be included under the
>>>>> testcases/kernel/hotplug/cpu_hotplug/functional directory.
>>>>
>>>> Why didn't you send this as a patch format?
>>>
>>> This was a frst attempt at sending test cases to LTP,so thought would get it
>>> reviewed as an RFC first.
>>
>> Yeah, but you can also send a patch titled like [RFC PATCH] xxx.
>
> Ok.
>>
>>>
>>>> Some comments below.
>>>>
>>>>>
>>>>> Regards
>>>>> Preeti
>>>>> ---
>>>>>
>>>>> # File : stress_cpu_hotplug.sh
>>>>> # Description : Switches the online state of all the cpus in a
>>>>> # loop to test the robustness of cpu hotplug
>>>>> # : The loop iteration of 20 is a randomly chosen number
>>>>>
>>>>> #! /bin/bash
>>>>>
>>>>> # Includes:
>>>>> LHCS_PATH=${LHCS_PATH:-$LTPROOT/testcases/bin/cpu_hotplug}
>>>>> . $LHCS_PATH/include/hotplug.fns
>>>>> . $LHCS_PATH/include/testsuite.fns
>>>>>
>>>>> setup()
>>>>> {
>>>>> export TST_TOTAL=1
>>>>> export TCID="setup"
>>>>> export TST_COUNT=0
>>>>>
>>>>> trap "cleanup" 0
>>>>> RC=0
>>>>>
>>>>> return $RC
>>>>>
>>>>> }
>>>>> cleanup()
>>>>> {
>>>>> set_all_cpu_state "$STATE"
>>>>
>>>> I can't find the definition of "$STATE" in your test script.
>>>
>>> I apologise for this typo.It needs to be $state as you have pointed out
>>> below.
>>>>
>>>>> }
>>>>>
>>>>> test01()
>>>>> {
>>>>>
>>>>> TCID="stress_cpu_hotplug"
>>>>> TST_COUNT=1
>>>>> RC=0
>>>>>
>>>>> NUMBER_OF_CPUS=`ls -d /sys/devices/system/cpu/cpu[0-9]* | wc -l`
>>>>>
>>>>> cd /sys/devices/system/cpu
>>>>>
>>>>> for ARRAY_INDEX in `seq 20`
>>>>> do
>>>>> for ((i=1; i < NUMBER_OF_CPUS; i++ ))
>>>>> do
>>>>> #skip the boot cpu;cannot offline it
>>>>> if [ $i -eq 0 ]
>>>>> then
>>>>> continue
>>>>> fi
>>>>>
>>>>> state=`cat cpu$i/online`
>>>>> if [ $state -eq 0 ]
>>>>> then
>>>>> RC=online_cpu $i
>>>>> else
>>>>> RC=offline_cpu $i
>>>>> fi
>>>>
>>>> Can it always success? I suppose that it need a bit sleep for the
>>>> online/offline time delay.
>>>
>>> It does not need a sleep because we are doing an online and offline of
>>> different cpus in one loop.i.e.for example:cpu1->1,cpu2->0,cpu3->1. so it
>>> takes one complete loop for cpu1->0 to occur which is enough time for an
>>> online or an offline operation for a cpu.
>>>
>>> Besides this,the test has been carried out on RHEL distros before and they
>>> have
>>> succeeded.Only the snapshot 5 of RHEL 6.3 is failing after running for a
>>> few seconds which
>>> is equivalent to nearly two loops.
>>
>> Did you investigate this problem? Why does it fail? Kernel problem or any
>> others?
>
> Yes,it is a kernel problem.The dmesg output showed that the cpu hotplug
> operation hangs at
> synchronize_sched().The scheduler is waiting for some rcu read side critical
> section to complete,and is either not notified of the completion of the task
> or there is some rcu section which is actually not completed.
>
> The machine is responsive,in the sense that it responds to the ping
> packets,but is too slow to perform any operation on.But slowly recovers back
> to the original state.We have opened a bug on this.
Ok, thank you.
Wanlong Gao
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