A simple user-space thread scheduler
Usage: Compile by running "make" Execute by running "./scheduler" *Redirecting output to log is recomened as there is a lot of info printed.
Configuration: The number of threads and the number of tasks perfomred by each thread are randomized. Limits are set in theApp.c. NUM_THREADS_BASE: Mininum number of threads. NUM_THREADS: Max number of threads to be generated from the base value THREAD_RUNS_BASE: Mininum number of tasks to perform for a thread. THREAD_RUNS: MAX number of tasks to perform from the base value.
Revision History:
The initial version of the thread scheduler is a restatement of the code given to us by Prof. Brandt. It still doesn't work, but when it does, we should be able to run it and play around with it before the actual assignment is posted.
thread_list is a linked list which will be used to make the lottery ticket system work. Currently, the list functions as a basic list, but I think we're going to need it because while the array Brandt gave us in the assignment is needed to make the thread context switching work, we're using the linked list to keep track of lottery tickets for the main scheduling subroutines.
Also, the current make targets are as follows:
- main: the main program we're going to turn in
- test: the thread list testing program
- clean: git rid o' dat shit
Went scorched earth and redid the entire master branch
I modified the way lists get deleted and added to. One adds data to a list by calling insertData(TLRef L, void *data, int tickets), and a node is automatically created and inserted into the list.
To delete a list, you must first clear it out using clearList(TLRef L). This function frees every node on the list in preparation for the list to be deleted. After calling this function, you can then call freeList(TLRef L) to finish the job.
I had to make a few changes to some of the files so that they would work with my new list First: I changed the name of the list references to the following for more clarity:
ThreadList -> TLRef
ThreadListNode -> TNRef
Second: I fixed the errors GCC was throwing with respect to scheduler.c and the_app.c
define _XOPEN_SOURCE
include <ucontext.h>
gets called before main() now. Also, I added threads.c's functions in stub-form to the_app.c until we figure out what to do with them.
Also, I haven't done anything to this effect, but I'd like to pose the following concern here:
I fail to see the use in keeping a separate "thread_object" object in addition to the list. It seems to be something we can use thread list nodes to do. If we keep the context variable and thread ID inside the list, then there's nothing else we need to do. We can just invoke the context change from a random thread by randomizing an index, selecting that random index off of the list, and using the resultant node reference to extract the context we want to go into after setting the timer.
Tyler redid most of the code comprising scheduler.c, which included a rewrite of thread_object within that file. This means that thread_object is now deprecated, and subject to deletion when scheduler is doing its job.
thread_list can now be freed using a single function, freeList(TLRef *pL). This function calls clear_list() by itself, but that function is still accessible in case one wants to clear the list without deleting it.
init_scheduler() is now called separately from thread_create. From within main. I determined that the pThrObj being created in init_scheduler() was passing pointers to objects in the local scope which were destroyed when init_scheduler returned. main_thread and all of its components are now global. (they do this on die.net's example too: http://linux.die.net/man/3/makecontext) the other contexts are fine, because their functions don't exit until they're ready.
I also added code to free the pThrObj when a thread exits.
From my perspective, this all works, and it all works without my slapdash context insertion (although, after asking my dad, he told me that this was not necessarily "wrong"... just totally unnecesary)