On Fri, 7 May 1999, Matthew Dillon wrote: > :> :--- uthread_create.c 1999/03/23 05:07:55 1.12 > :> :+++ uthread_create.c 1999/05/06 15:27:33 > :> :@@ -42,6 +42,8 @@ > :> : #include "pthread_private.h" > :> : #include "libc_private.h" > :> : > :> :+static int next_tid = 1; > :> :+ > :> : int > :> : pthread_create(pthread_t * thread, const pthread_attr_t * attr, > :> : void *(*start_routine) (void *), void *arg) > :> :@@ -87,6 +89,7 @@ > :> : } else { > :> : /* Initialise the thread structure: */ > :> : memset(new_thread, 0, sizeof(struct pthread)); > :> :+ new_thread->tid = next_tid++; > :> : > :> :Doug Rabson Mail: d...@nlsystems.com > :> :Nonlinear Systems Ltd. Phone: +44 181 442 9037 > :> > :> Hmmm. tid is only an int and some programs which create and destroy > :> threads a lot are almost certainly going to overflow it. 4 billion > :> is not hard to reach. This can result in duplicate tid's. > : > :Didn't think of that. It gets a bit ugly inside gdb since gdb needs a > :single int to encode the pid and thread id. I'm currently allowing 20 > :bits for the pid and 11 for the tid. Any ideas? > : > :-- > :Doug Rabson Mail: d...@nlsystems.com > :Nonlinear Systems Ltd. Phone: +44 181 442 9037 > > Hmmm. 11 bits is only 2048 threads. You are going to have problems > no matter what. > > You could have a pool of tid structures. A simple freelist. Pseudo > code below. This would fix the unique-tid problem but it would not fix > the 2048 thread limit with gdb.
I can probably increase the field size of the tid up to about 14 bits (we only have pids going up to 100000 I think). I would rather not do this amount of work inside uthread; perhaps it would be better to make the uthread store a 64bit unique number and then compress it down to a 14 bit tid inside gdb by keeping a hash table or something similar. Its going to be pretty hard to debug a program with 16k active threads so I think this limit should be ok. -- Doug Rabson Mail: d...@nlsystems.com Nonlinear Systems Ltd. Phone: +44 181 442 9037 To Unsubscribe: send mail to majord...@freebsd.org with "unsubscribe freebsd-current" in the body of the message