trying to fix timing bugs
Merge branch 'master' of https://github.com/fchoo/lab4
Merge branch 'master' of https://github.com/fchoo/lab4

Conflicts:
	kernel/sched/ctx_switch.c
merged
added helper to change cur_task
wrote mutex lock
Merge branch 'master' of https://github.com/fchoo/lab4
added helper dispatchers for ctx switching mutexes
added mutex unlock