I found there is no 'sched.h' in /usr/include while 'sys/sched.h' says:

/*
 * Posix defines a <sched.h> which may want to include <sys/sched.h>
 */

This is file is needed by mysql-3.22.32. Anyone knows the details?

     .------------------------------------------.
     |     Sonnie  Hook     |  sonnie@ustc.edu  |
     |------------------------------------------|
     |  the State Key Lab. of Fire Sci. (SKLFS) |
     | the Uni. of Sci. & Tech. of China (USTC) |
     `------------------------------------------'