[OLSR-users] Spurios crashes (SIGSEGV) on exit in 0.5.0 (and earlier)

[Joerg Pommnitz]

Hello all,
I just bothered to look at spurious crashes I have observed with olsrd for a long time.

It turns out that olsr_shutdown gets called from signal context and uses
forbidden library calls. The crash I observed was in vsyslog, but I'm sure
other things could go wrong as well. In Unix only a very limited subset of
C library functions is signal safe and may be used from signal handlers (see http://www.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html
for the full list).

Looking at olsr_shutdown gave me a creepy feeling. This function must never
be called from a signal context. The right way would be to handle this signal
synchronous.

In Unix you can turn an asynchronous signal into a synchronous notification by
opening a pipe and writing the signal number in the write end and poll the read end
for activity (write is signal safe).
 
--  
Regards
 
       Joerg
 






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