I re-installed glibc-2.3.4-2.39.src.rpm on CentOS 4.6, and tried to use pthread_setschedprio() API in glibc library, but it fails. Here is my system information. Operating System CentOS 4.6 (x86_64), Linux version 2.6.9-67.Elsmp gcc version 3.4.6 20060404 (Red Hat 3.4.6-9) glibc (pthread) src glibc-2.3.4-2.39.src.rpm I checked that setschedprio function is in the GLIB_2.3.4 but I got following errors [root at localhost TMP]# gcc d.c -o d -lpthread /tmp/ccEeiBLd.o(.text+0x179): In function `main': : undefined reference to `pthread_setschedprio' collect2: ld returned 1 exit status Can I get any advice to use that API?