1 / 25

Reminders

Reminders. Start project 2! It’s long Read the assignment carefully Read it again Make sure your groups are correct Today: Project 2 intro CVS. Project 2. You have to: Implement a user thread library Implement synchronization primitives Solve a synchronization problem Add Preemption

farhani
Download Presentation

Reminders

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Reminders • Start project 2! • It’s long • Read the assignment carefully • Read it again • Make sure your groups are correct • Today: • Project 2 intro • CVS

  2. Project 2 • You have to: • Implement a user thread library • Implement synchronization primitives • Solve a synchronization problem • Add Preemption • Implement a multithreaded web server • Get some results and write a (small) report • Part a due: in two weeks • Part b due: 9 days after part a Part a Part b

  3. Simplethreads • We give you: • Skeleton functions for thread interface • Machine-specific code • Support for creating new stacks • Support for saving regs/switching stacks • A generic queue • When do you need one? • Very simple test programs • You should write more • Singlethreaded web server

  4. Simplethreads Code Structure test/*.c Web server (web/sioux.c) Other apps include/sthread.h You write this lib/sthread_user.c lib/sthread_user.h lib/sthread_queue.h lib/sthread_ctx.h lib/sthread_preempt.h lib/sthread_queue.c lib/sthread_ctx.c lib/sthread_preempt.c lib/sthread_switch.S sthread_switch_i386.h sthread_switch_powerpc.h

  5. Thread Operations • Which ones do we need?

  6. Thread Operations • void sthread_init() • Initialize the whole system • sthread_t sthread_create(func start_func, void *arg) • Create a new thread and make it runnable • void sthread_yield() • Give up the CPU • void sthread_exit(void *ret) • Exit current thread • What about the TCB? struct _thread { sthread_ctx_t *saved_ctx; ……… } • Others?

  7. Sample multithreaded program int main(int argc, char **argv) { int i; sthread_init(); for(i=0; i<3; i++) if (sthread_create(thread_start, (void*)i) == NULL) { printf("sthread_create failed\n"); exit(1); } sthread_yield(); printf("back in main\n"); return 0; } void *thread_start(void *arg) { printf("In thread_start, arg = %d\n", (int)arg); return 0; } • Output? (assume no preemption)

  8. Managing Contexts (given) • Thread context = thread stack + stack pointer • sthread_new_ctx(func_to_run) • gives a new thread context that can be switched to • sthread_free_ctx(some_old_ctx) • Deletes the supplied context • sthread_switch(oldctx, newctx) • Puts current context into oldctx • Takes newctx and makes it current

  9. How sthread_switch works Thread 1 TCB … SP Thread 2 TCB … SP Xsthread_switch: pusha movl %esp,(%eax) movl %edx,%esp popa ret Thread 2 registers CPU ESP Thread 1 running Thread 2 ready Thread 1 regs Want to switch to thread 2…

  10. Push old context Thread 1 TCB … SP Thread 2 TCB … SP Xsthread_switch: pusha movl %esp,(%eax) movl %edx,%esp popa ret Thread 1 registers Thread 2 registers CPU ESP Thread 1 running Thread 2 ready Thread 1 regs

  11. Save old stack pointer Thread 1 TCB … SP Thread 2 TCB … SP Xsthread_switch: pusha movl %esp,(%eax) movl %edx,%esp popa ret Thread 1 registers Thread 2 registers CPU ESP Thread 1 running Thread 2 ready Thread 1 regs

  12. Change stack pointers Thread 1 TCB … SP Thread 2 TCB … SP Xsthread_switch: pusha movl %esp,(%eax) movl %edx,%esp popa ret Thread 1 registers Thread 2 registers CPU ESP Thread 1 ready Thread 2 running Thread 1 regs

  13. Pop off new context Thread 1 TCB … SP Thread 2 TCB … SP Xsthread_switch: pusha movl %esp,(%eax) movl %edx,%esp popa ret Thread 1 registers CPU ESP Thread 1 ready Thread 2 running Thread 2 regs

  14. Done; return Thread 1 TCB … SP Thread 2 TCB … SP Xsthread_switch: pusha movl %esp,(%eax) movl %edx,%esp popa ret Thread 1 registers • What got switched? • SP • PC (how?) • Other registers CPU ESP Thread 1 ready Thread 2 running Thread 2 regs

  15. Adjusting the PC Thread 1 TCB … SP Thread 2 TCB … SP • ret pops off the new return address! Thread 1 registers ra=0x400 ra=0x800 CPU ESP Thread 1 (stopped): switch(t1,t2); 0x400: printf(“test 1”); Thread 2 running: switch(t2,...); 0x800: printf(“test 2”); PC

  16. Things to think about • Who will call sthread_switch? • Where does sthread_switch return? • How do we delete a thread? • Can a thread free its stack itself? • Starting up a thread • When you create a new stack with sthread_new_ctx(), you initialize it to run some function foo • sthread_new_ctx doesn’t pass parameters to foo • But in sthread_create, you give a function and an arg! • Bottom line: how do you pass arguments to a function with no arguments?

  17. Preemption • Initially, you will build a non-preemptive thread library. • In part 4, you add preemption • Much more realistic model • We give you: • Timer interrupts • Primitives to enable/disable interrupts • atomic_test_and_set/atomic_clear for synchronization • You must: • Do something on each timer interrupt. (What?) • Synchronize all of your code using 2 and 3 above. • More on this later…

  18. Last note • You can compare your implementation against pthreads (which is preemptive kernel-threads). • ./configure --with-pthreads

  19. What is CVS • Version control system for source files • Multiple users can work on the same file simultaneously

  20. Why use CVS • The other way: • Keep every version of code, all with different names: • Project2good • Project2_10_13_04 • Project2working • Project2_Feb_2_alex • Project2_old • Send emails back and forth with new changes • Merge different versions by hand • The CVS way: • One version, saved in the CVS repository • Multiple people can work on the same file concurrently • CVS merges the edited versions automatically as you put them back in the repository

  21. Setting up CVS • Set up CVS root • setenv CVSROOT /cse451/groupa/cvs • (bash)export CVSROOT=/cse451/groupa/cvs • Initialize a repository (only one person per group) • cd /cse451/groupa • mkdir cvs • cvs init

  22. Setting up CVS (2) • Add the simplethreads distribution • tar xvfz simplethreads-1.20.tar.gz • cd simplethreads-1.20 • cvs import –m “initial code” simplethreads SIMPLETHREADS SIMPLETHREADS_1_20 • cd .. • rm –fr simplethreads-1.20

  23. CVS Commands • Check out a project to your home directory: • cd ~ • cvs checkout simplethreads • Merge in new changes from repository (update): • cvs update [files…] • Save your edited files into the repository: • cvs commit –m “fixed annoying bugs” [files…]

  24. CVS Commands 2 • Add a new file to the repository • cvs add [files…] • Check status of a file • cvs status file.c • Check differences between your file and one in the repository: • cvs diff file.c • cvs diff –r 1.1 file.c (specifies version) • View log of changes for a file • cvs log file.c • More info: • http://www.cvshome.org • cvs --help-commands

  25. CVS Remote Access • Access CVS from another machine: • setenv CVSROOT coredump.cs.washington.edu:/cse451/cse451a/cvs • setenv CVS_RSH ssh (for CVS to know how to access repository)(add to ~/.login (csh) or ~/.profile (bash))

More Related