Eric Noulard wrote:
> Hi all,
>
> I've recently discovered a "possible" bug
> only occuring with a system running xenomai-patched kernel.
>
> I have set up a machine (dual-core intel machine).
> The machine is installed with a Fedora Core 6 and
> may be booted (test purpose) with different kernel:
>
> 1) linux 2.6.20-0119.rt8
> which is an Ingo Molnar precompiled preempt-rt patched kernel
> you may find it there:
> http://people.redhat.com/mingo/realtime-preempt/
>
> 2) 2.6.20-xeno-2.3.1-ipipe-1.7-03
> which is a xenomai enabled kernel I've configured and compiled.
>
> My test application is a mixed C/C++ USER-land application
> which currently make no xenomai specific call.
>
> The application core dumps at the end of its execution
> with the xenomai enabled kernel whereas it does not
> with the preempt-rt kernel.
>
> I track down the problem to a misuse of sigaction calls
> which install SIGALARM handler with sa_flags not properly setup.
>
> My code is definitely buggy but I let you know because in the first
> place it was puzzling to have different (but consistent and repeatable)
> behavior
> on different kernel, with core dump using the Xenomai-enabled kernel :((.
>
> You may try it yourself:
>
> gcc -o BadTimerSigHandler TimerSigHandler.c
>
> generates a the buggy binary, while
>
> gcc -DGOOD_SIGHANDLING -o GoodTimerSigHandler TimerSigHandler.c
>
> generates the good one.
>
> I don't really know if it may indicates a xenomai bug or not
> but I would be glad to understand WHY is this.
>
> I mean I know that uninitialized memory have unpredictable consequence
> but here the bug is persistent after rerun, reboot, power cycle etc...
>
>
>
>
> ------------------------------------------------------------------------
>
> #include <stdio.h>
> #include <sys/types.h>
> #include <signal.h>
>
> static int stop = 0;
>
> void
> SignalHandler(int Signal) {
> int pid = getpid();
> printf("Received signal %d. Stopping peacefully.\n", Signal);
> stop = 1;
> }
>
>
> int
> main() {
>
> int i;
> struct sigaction a ;
>
> signal(SIGINT , SignalHandler);
> signal(SIGPIPE, SignalHandler);
>
> a.sa_handler = SignalHandler ;
> sigemptyset(&a.sa_mask);
> #if defined(GOOD_SIGHANDLING)
> a.sa_flags = SA_RESTART;
> #endif
You should initialize sa_flags with the bugous value on your platform,
different platforms, different compilers may lead to a different value
of sa_flags here, possibly preventing us from seeing the bug.
--
Gilles Chanteperdrix
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