README revision 1.3
1 1.1 proven This pthread package is/will be based on the POSIX1003.4a Draft 7 pthread 2 1.1 proven standard, and Frank Mullers paper on signal handelling presented 3 1.1 proven at the Winter 93 USENIX conference. 4 1.1 proven 5 1.1 proven It is currently being designed and written by me, Chris Provenzano. 6 1.1 proven All bug, comments, and questions can be sent me at either 7 1.1 proven proven (a] athena.mit.edu or proven (a] sun-lamp.cs.berkeley.edu 8 1.3 proven PLEASE, don't send questions, bugs or patches to any of the *BSD* mailing lists. 9 1.1 proven 10 1.1 proven Thanks goes to John Carr jfc (a] mit.edu for porting this to the IBM/RT, 11 1.3 proven and for his bug reports and fixes, Greg Hudson and Mark Eichin for the 12 1.3 proven testing they've done, and all the others. 13 1.1 proven 14 1.1 proven PORTING 15 1.1 proven One of the goals of this user space implementation of pthreads is that it 16 1.1 proven be portable. I have minimized the ammount of assembler code necessary, 17 1.1 proven but some is. 18 1.1 proven 19 1.1 proven If you want to port it to another platform here are a few basic hints. 20 1.1 proven 21 1.1 proven There are currently three files you'll have to creat for your 22 1.1 proven architecture, machdep.h, machdep.c and syscall.S. 23 1.1 proven The first two are necessary to get the context switch section of 24 1.1 proven the pthread package running, the third is for all the syscalls. 25 1.1 proven 26 1.1 proven To do an initial port, create an appropriate machdep.h, and machdep.c 27 1.1 proven and define PTHREAD_INITIAL_PORT in the Makefile 28 1.1 proven 29 1.1 proven Comment out references to the stdio package. 30 1.1 proven 31 1.1 proven INCLUDE FILES AND PORTING 32 1.1 proven To continue to make this package portable, some basic rules on includes 33 1.1 proven files must be followed. 34 1.1 proven 35 1.1 proven pthread.h should be included first (if it is to be included). 36 1.1 proven machdep.h should define size_t if the system doesn't define it already 37 1.1 proven 38 1.1 proven posix.h should be included last. This file is used to correct non 39 1.1 proven POSIX features, after everything else has been defined. 40 1.1 proven 41 1.1 proven INTERNAL LOCKING 42 1.1 proven To prevent deadlocks the following rules were used for locks. 43 1.1 proven 44 1.1 proven 1. Local locks for mutex queues and other like things are only locked 45 1.1 proven by running threads, at NO time will a local lock be held by 46 1.1 proven a thread in a non running state. 47 1.1 proven 2. Only threads that are in a run state can attempt to lock another thread, 48 1.1 proven this way, we can assume that the lock will be released shortly, and don't 49 1.1 proven have to unlock the local lock. 50 1.1 proven 3. The only time a thread will have a pthread->lock and is not in a run 51 1.1 proven state is when it is in the reschedule routine. 52 1.1 proven 4. The reschedule routine assumes all local locks have been released, 53 1.1 proven there is a lock on the currently running thread (pthread_run), 54 1.1 proven and that this thread is being rescheduled to a non running state. 55 1.1 proven It is safe to unlock the currently running threads lock after it 56 1.1 proven has been rescheduled. 57 1.1 proven 5. The reschedule routine locks the kernel, sets the state of the currently 58 1.1 proven running thread, unlocks the currently running thread, calls the 59 1.1 proven context switch routines. 60 1.1 proven 6 the kernel lock is used only ... 61 1.1 proven 62 1.1 proven 63 1.1 proven 7. The order of locking is ... 64 1.1 proven 65 1.1 proven 1 local locks 66 1.1 proven 2 pthread->lock /* Assumes it will get it soon */ 67 1.1 proven 3 pthread_run->lock /* Assumes it will get it soon, but must release 2 */ 68 1.1 proven 4 kernel lock /* Currently assumes it will ALWAYS get it. */ 69 1.1 proven 70 1.1 proven 8. The kernel lock will be changed to a spin lock for systems that 71 1.1 proven already support kernel threads, this way we can mutiplex threads onto 72 1.1 proven kernel threads. 73 1.1 proven 9. There are points where the kernel is locked and it needs to get 74 1.1 proven either a local lock or a pthread lock, if at these points the code 75 1.1 proven fails to get the lock the kernel gives up and sets a flag which will 76 1.1 proven be checked at a later point. 77 1.1 proven 10. Interrupts are dissabled while the kernel is locked, the interrupt 78 1.1 proven mask must be checked afterwards or cleared in some way, after interrputs 79 1.1 proven have been reenabled, this allows back to back interrupts, but should always 80 1.1 proven avoid missing one. 81 1.1 proven 82 1.1 proven Copyright (c) 1993 Chris Provenzano. All rights reserved. 83 1.1 proven 84 1.1 proven This product includes software developed by the Univeristy of California, 85 1.1 proven Berkeley and its contributors. 86
Indexes created Sun Nov 02 23:10:09 GMT 2025