Re: [Xenomai] [xenomai-forge] timer-internal consume a lot of cpu

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2014-12-18 15:12, Gilles Chanteperdrix wrote:
> On Thu, Dec 18, 2014 at 01:28:42PM +0100, Ronny Meeus wrote:
>> On Thu, Dec 18, 2014 at 10:04 AM, Jan Kiszka <jan.kiszka@siemens.com> wrote:
>>> On 2014-12-18 09:00, Ronny Meeus wrote:
>>>>>
>>>>> A release of the glibc that fixes this issue. I must admit that I did
>>>>> not track this problem lately. Jan likely knows better here.
>>>>>
>>>>
>>>> Jan,
>>>>
>>>> what version glibc solves the priority inversion issue on conditional variables?
>>>> I already tried the glibc 2.18 but the issue is still there.
>>>
>>> The bug is still not fixed, and discussion stalled again, see
>>> https://sourceware.org/bugzilla/show_bug.cgi?id=11588
>>>
>>> Jan
>>>
>>> --
>>> Siemens AG, Corporate Technology, CT RTC ITP SES-DE
>>> Corporate Competence Center Embedded Linux
>>
>> Philippe, Jan
>>
>> as long as this issue is not fixed in glibc, it is not OK to use
>> conditional variables
> 
> I believe xenomai cobalt does not suffer from the same issue,
> condition variables should work fine with priority inheritance.

Yes, this is a mercury-only issue. Cobalt is fine as its own
implementation of posix mutexes and condvars is correct in this regard.

> 
> Otherwise, have you tried some alternate libc, such as musl:
> http://www.musl-libc.org/
> 
> The following blog:
> http://ewontfix.com/
> 
> Seems to show that the musl maintainers try and report glibc bugs
> and avoid them in their implementation.
> 
> I have not tried xenomai with musl at all, so, maybe it does not
> even compile. But maybe just compiling a testcase for the condvar
> issue with that libc would help know if it has the same issue or
> not.

Well, like with many of those "light-weight" re-implementations, the are
"small" issues with bits required for real-time:

http://git.musl-libc.org/cgit/musl/tree/src/thread/pthread_mutexattr_setprotocol.c

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux