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Date: Mon, 02 Nov 2009 08:43:06 +0100
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-core] lots of mode switches in xenomai-head tree?
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To: Stefan Schaal <sschaal@domain.hid>
Cc: Jonas Buchli <jonas@domain.hid>, Peter Pastor Sampedro <pastorsa@domain.hid>, xenomai@xenomai.org

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Stefan Schaal wrote:
> Hi,
>=20
>    I am working with the latest xenomai-head tree (we need analogy for =
=20
> our NI board ...). Under Xenomai 2.4.8 our code did not have any mode  =

> switches. Using the xenomai-head, we get a lot of mode switches. Using =
=20
> he backtrace_symbols_fd, we get print-outs like:
>=20
>=20
> xsimulation[0x808553b]
> [0xffffe400]
> /usr/xenomai/lib/librtdk.so.0(assert_nrt+0x85)[0xb7fa2ea5]
> /usr/xenomai/lib/librtdk.so.0(__wrap_clock_gettime+0x17)[0xb7fa2ef7]
> xsimulation[0x807cd16]
> xsimulation[0x807d7fb]
> /usr/xenomai/lib/libnative.so.3[0xb7fab689]
> /lib/tls/i686/cmov/libpthread.so.0[0xb7f824ff]
> /lib/tls/i686/cmov/libc.so.6(clone+0x5e)[0xb7e8f49e]
>=20
> Which indicates that the wrapper for clock_gettime causes this =20
> trouble, which is also confirmed by commenting clock_gettime out, and  =

> the  mode switches disappear.
>=20
>   Maybe something that needs fixing?

Do you wrap & link against the POSIX library, ie. use that skin as well?
If not, your code is actually using clock_gettime incorrectly as it then
falls back to the Linux service which can trigger syscalls (or even
deadlocks when the TSC is used).

If you do use libpthread_rt, then my next question is if your work is
based on today's git head or some older version not including 4a2cb7b817.=


Jan


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