Re: SystemTap for Android - patchset

[Alexander Lochmann <alexander dot lochmann at tu-dortmund dot de>]

On 07.07.2016 21:24, David Smith wrote:
> On 07/07/2016 02:01 PM, Alexander Lochmann wrote:
>> On 07.07.2016 20:47, David Smith wrote:
>>> On 07/06/2016 07:29 AM, Alexander Lochmann wrote:
>>>> So. Let me start.
>>>> First of all, I extracted the patches properly, and attached the files.
>>>> (Btw, I found a third bug. :) )
>>>> FYI, I just fixed the bugs for the kernel versions I'm dealing with,
>>>> because I don't know which other versions are affected as well.
>>>
>>> The problem you are trying to fix in your patch "[PATCH 1/3] Definition
>>> of cputime_to_usecs in Linux kernel 3.0 is broken" is interesting. I
>>> don't think you've got quite the right solution. Testing for a kernel
>>> version here works for you, but really isn't a general solution -
>>> depending on arch there could be a kernel in that range with a
>>> reasonable cputime_to_usecs().
>> I see. :-/ Lesson learned.
>>>
>>> ====
>>> diff --git a/tapset/linux/task_time.stp b/tapset/linux/task_time.stp
>>> index f86f984..f3c276c 100644
>>> --- a/tapset/linux/task_time.stp
>>> +++ b/tapset/linux/task_time.stp
>>> @@ -27,8 +27,12 @@
>>>   * Yet note some kernels (RHEL6) may already have both...  */
>>>  #if defined(cputime_to_usecs)
>>>  #if !defined(cputime_to_msecs)
>>> +#if LINUX_VERSION_CODE <= KERNEL_VERSION(3,0,200) && LINUX_VERSION_CODE
>>>> = KERNEL_VERSION(3,0,0)
>>> +#define cputime_to_msecs(__ct)		_stp_div64(NULL,
>>> ({cputime_to_usecs(__ct)}), 1000ULL)
>>> +#else
>>>  #define cputime_to_msecs(__ct)		_stp_div64(NULL,
>>> cputime_to_usecs(__ct), 1000ULL)
>>>  #endif
>>> +#endif
>>>
>>>  /* Kernels before 2.6.37 have cputime_to_msecs, but not usecs. */
>>>  #elif defined(cputime_to_msecs)
>>> ====
>>>
>>> I've got a couple of thoughts here:
>>>
>>> - I wonder if we just couldn't always use your workaround (along with a
>>> comment about why we're doing that).
>> Why not? :) Since the kernel and every module of course is compiled with
>> -O3 (or -O2?),  it shouldn't make any difference in the resulting
>> assembler code.
> 
> Right. So, I checked in your fix as commit 2cc20af.
> 
Thanks. :)
> Thanks.
> 


-- 
Technische Universität Dortmund
Alexander Lochmann                PGP key: 0xBC3EF6FD
Otto-Hahn-Str. 16                 phone:  +49.231.7556141
D-44227 Dortmund                  fax:    +49.231.7556116
http://ess.cs.tu-dortmund.de/Staff/al

Attachment: signature.asc
Description: OpenPGP digital signature