Wednesday, November 28, 2007

Did I find the rsyslog bug?

I have a new leading theory on the rsyslog segfault bug. Before I restructured everything to get rid of the alarm() calls, I did some more research in respect to the best threading model. More or less by accident, I found a nice note on glibc, rentrancy and the _REENTRANT preprocessor macro. That lead me to the "-pthread" compiler option...

May it be that we "just" have a compiler option problem? So far, we only call it with "-lpthreads", which only effects the linker. -pthread, if I understood it right, defines _REENTRANT, which in turn causes some reentrant versions of standard library functions to be used. If that isn't outdated information, it could pretty much be our problem.

I am not sure which functions of the run time library are affected by the _REENTRANT macro. So I do not know if I call them. However, non-reentrant run time library functions would be a good explanation for very seldom segfaults that only occur under heavy load and when running in multithreading mode. It would also explain why so many in-depth code reviews did not find anything...

This compiler option finding looks very promising. I'll probably do a special 1.19.11 release with just that patch and then we'll see what happens. In the mean time, I wait if somebody comes up with some more diagnostic information. But I finally have found a good explanation for what I see - at least in theory...

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Busy at the moment...

Some might have noticed that I am not as active as usual on the rsyslog project . As this seems to turn out to keep at least for the upcomi...