Bad system call - sigprocmask

[Jan Danielsson <jan.m.danielsson%gmail.com@localhost>]

Hello,

   I have a system which reads I2C data from a few sensors and stores
their data in shared memory which is protected using a shared semaphore.

   In order to prevent a deadlock among other processes if a process is
killed while it's holding the lock I temporarily block SIGTERM and
SIGINT while the process owns the lock [while modifying the shared data].

   I run the processes as a regular user, with the exception of an SNMP
agent which runs as root.

   What I'm seeing is:
   - For two processes (which I run as a regular user), everything works
fine and I've set up SIGINT and SIGTERM handlers using sigaction().
   - The SNMP agent sets up handlers for SIGINT and SIGTERM using
signal(), and the process is run as root.  When this function calls
sigprocmask() in order to temporarily block the signals, it crashes and
prints out "Bad system call".

   Anyone know why sigprocmask() could be failing so hard in the third
process?

-- 
Kind Regards,
Jan