system() call causes core dump

[Peter Steele]

I have an application running a number of threads. I've had recent instances where the code below is causing a core dump to occur:

char fstatCmd[200];
char *fstatOut = "/tmp/fstat.out";
sprintf(fstatCmd, "fstat | grep -v USER | wc -l >%s", fstatOut);
rc = system(fstatCmd);

The call is simply intended to get a count of the current open handles. The system call though causes a core:

#0 0x0000000801058307 in _spinunlock () from /lib/libthr.so.3
#1 0x00000008011d0afb in _malloc_postfork () from /lib/libc.so.7
#2 0x000000080105c5fb in fork () from /lib/libthr.so.3
#3 0x0000000801191aae in system () from /lib/libc.so.7
#4 0x00000008010553aa in system () from /lib/libthr.so.3
#5 0x000000000040b6f9 in mythread at myapp.c:461
#6 0x0000000801056a88 in pthread_getprio () from /lib/libthr.so.3

There appears to be some kind of thread-safe issue going on. I have a number of threads that are monitoring various items, waking up a differing intervals to do their respective tasks. Do I need to put in a global mutex so that the threads never attempt to make simultaneous system() calls? Curiously, only this particular system() call appears to be causing a core.