README revision 1.1
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 1.1 proven Please don't send bugs or patches to any of the NetBSD 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 1.1 proven and for his bug reports and fixes. 12 1.1 proven 13 1.1 proven PORTING 14 1.1 proven One of the goals of this user space implementation of pthreads is that it 15 1.1 proven be portable. I have minimized the ammount of assembler code necessary, 16 1.1 proven but some is. 17 1.1 proven 18 1.1 proven If you want to port it to another platform here are a few basic hints. 19 1.1 proven 20 1.1 proven There are currently three files you'll have to creat for your 21 1.1 proven architecture, machdep.h, machdep.c and syscall.S. 22 1.1 proven The first two are necessary to get the context switch section of 23 1.1 proven the pthread package running, the third is for all the syscalls. 24 1.1 proven 25 1.1 proven To do an initial port, create an appropriate machdep.h, and machdep.c 26 1.1 proven and define PTHREAD_INITIAL_PORT in the Makefile 27 1.1 proven 28 1.1 proven Comment out references to the stdio package. 29 1.1 proven 30 1.1 proven INCLUDE FILES AND PORTING 31 1.1 proven To continue to make this package portable, some basic rules on includes 32 1.1 proven files must be followed. 33 1.1 proven 34 1.1 proven pthread.h should be included first (if it is to be included). 35 1.1 proven machdep.h should define size_t if the system doesn't define it already 36 1.1 proven 37 1.1 proven stdio.h should not be included. It is included in pthread.h. 38 1.1 proven 39 1.1 proven posix.h should be included last. This file is used to correct non 40 1.1 proven POSIX features, after everything else has been defined. 41 1.1 proven 42 1.1 proven INTERNAL LOCKING 43 1.1 proven To prevent deadlocks the following rules were used for locks. 44 1.1 proven 45 1.1 proven 1. Local locks for mutex queues and other like things are only locked 46 1.1 proven by running threads, at NO time will a local lock be held by 47 1.1 proven a thread in a non running state. 48 1.1 proven 2. Only threads that are in a run state can attempt to lock another thread, 49 1.1 proven this way, we can assume that the lock will be released shortly, and don't 50 1.1 proven have to unlock the local lock. 51 1.1 proven 3. The only time a thread will have a pthread->lock and is not in a run 52 1.1 proven state is when it is in the reschedule routine. 53 1.1 proven 4. The reschedule routine assumes all local locks have been released, 54 1.1 proven there is a lock on the currently running thread (pthread_run), 55 1.1 proven and that this thread is being rescheduled to a non running state. 56 1.1 proven It is safe to unlock the currently running threads lock after it 57 1.1 proven has been rescheduled. 58 1.1 proven 5. The reschedule routine locks the kernel, sets the state of the currently 59 1.1 proven running thread, unlocks the currently running thread, calls the 60 1.1 proven context switch routines. 61 1.1 proven 6 the kernel lock is used only ... 62 1.1 proven 63 1.1 proven 64 1.1 proven 7. The order of locking is ... 65 1.1 proven 66 1.1 proven 1 local locks 67 1.1 proven 2 pthread->lock /* Assumes it will get it soon */ 68 1.1 proven 3 pthread_run->lock /* Assumes it will get it soon, but must release 2 */ 69 1.1 proven 4 kernel lock /* Currently assumes it will ALWAYS get it. */ 70 1.1 proven 71 1.1 proven 8. The kernel lock will be changed to a spin lock for systems that 72 1.1 proven already support kernel threads, this way we can mutiplex threads onto 73 1.1 proven kernel threads. 74 1.1 proven 9. There are points where the kernel is locked and it needs to get 75 1.1 proven either a local lock or a pthread lock, if at these points the code 76 1.1 proven fails to get the lock the kernel gives up and sets a flag which will 77 1.1 proven be checked at a later point. 78 1.1 proven 10. Interrupts are dissabled while the kernel is locked, the interrupt 79 1.1 proven mask must be checked afterwards or cleared in some way, after interrputs 80 1.1 proven have been reenabled, this allows back to back interrupts, but should always 81 1.1 proven avoid missing one. 82 1.1 proven 83 1.1 proven Copyright (c) 1993 Chris Provenzano. All rights reserved. 84 1.1 proven 85 1.1 proven This product includes software developed by the Univeristy of California, 86 1.1 proven Berkeley and its contributors. 87
Indexes created Tue Sep 23 23:09:58 GMT 2025