From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 06 Jul 2006 13:54:02 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
MIME-Version: 1.0
Subject: Re: [Xenomai-help] Detecting switch to secondary mode
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To: "J. Niehaus" <Niehaus@domain.hid>
Cc: xenomai@xenomai.org

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J. Niehaus wrote:
> Hello,
>=20
> I have written a xenomai application (posix-skin) with several tasks. A=
ll of them should normally use primary mode (SCHED_FIFO). While some are =
allowed to switch to secondary mode for stuff like I/O and memory allocat=
ion others must not switch due to hard realtime constraints.=20
>=20
> Is there a way to check if and how often a thread has switched to secon=
dary mode and maybe even what system call caused the switch? While a test=
 from within the program itself would be great some information from /pro=
c/xenomai would also do.
>=20

Yes, see this example:
http://www.rts.uni-hannover.de/xenomai/lxr/source/ksrc/skins/native/snipp=
ets/sigxcpu.c

We have the following code snippet in the signal handler of our RACK
framework:

void signal_handler(int sig)
{
[...]
    switch(sig)
    {
        case SIGXCPU:

            if (signal_flags & HANDLING_TERM) // ignore while
cleaning 		                                              // up
                return;

            printf("\n");
            printf("---=3D=3D=3D SIGNAL HANDLER of %s =3D=3D=3D---\n", cl=
assname);
            printf(" -> SIGXCPU (%02d)\n", sig);
            printf(" !!! WARNING unexpected switch to secondary mode "
                   "!!!\n");
            nentries =3D backtrace (array, 10);
            strings =3D backtrace_symbols (array, nentries);
            for (i =3D 0; i < nentries; i++)
            {
                printf ("  %s\n", strings[i]);
            }
            free (strings);
            printf("---=3D=3D=3D END OF %s SIGNAL HANDLER =3D=3D=3D---\n"=
,
                   classname);
            return;
[...]

I.e. it does a back-trace to show what happened in user-space (debug
symbols are required). It's VERY useful when letting beginners hack
their first RT applications.

Jan


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