cvs commit: src/sys/kern kern_fork.c kern_thr.c kern_thread.c
marcel at FreeBSD.org
Sat Apr 3 07:59:16 PST 2004
marcel 2004/04/03 07:59:13 PST
FreeBSD src repository
sys/kern kern_fork.c kern_thr.c kern_thread.c
Assign thread IDs to kernel threads. The purpose of the thread ID (tid)
1. When a 1:1 or M:N threaded process dumps core, we need to put the
register state of each of its kernel threads in the core file.
This can only be done by differentiating the pid field in the
respective note. For this we need the tid.
2. When thread support is present for remote debugging the kernel
with gdb(1), threads need to be identified by an integer due to
limitations in the remote protocol. This requires having a tid.
To minimize the impact of having thread IDs, threads that are created
as part of a fork (i.e. the initial thread in a process) will inherit
the process ID (i.e. tid=pid). Subsequent threads will have IDs larger
than PID_MAX to avoid interference with the pid allocation algorithm.
The assignment of tids is handled by thread_new_tid().
The thread ID allocation algorithm has been written with 3 assumptions
1. IDs need to be created as fast a possible,
2. Reuse of IDs may happen instantaneously,
3. Someone else will write a better algorithm.
Revision Changes Path
1.225 +1 -0 src/sys/kern/kern_fork.c
1.18 +1 -0 src/sys/kern/kern_thr.c
1.175 +98 -2 src/sys/kern/kern_thread.c
1.373 +2 -0 src/sys/sys/proc.h
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