CVS commit: src/sys

[Andrew Doran <ad%netbsd.org@localhost>]

Module Name:    src
Committed By:   ad
Date:           Fri Apr 11 14:55:51 UTC 2008

Modified Files:
        src/sys/kern: kern_rwlock.c
        src/sys/sys: rwlock.h

Log Message:
rwlock changes, discussed on tech-kern:

- Use atomic ops directly, since rwlocks work the same way on all platforms.
- Try to make it a bit more cache efficient, and use branch hints.
- Fix a bug in rw_downgrade() where the turnstile lock was not released.
- Remove a couple of redundant assertions.
- Use atomic_swap instead of atomic_cas where it's safe to do so.
- After acquiring the turnstile lock in rw_vector_enter, check if the
  owner is running again and spin if so.
- Introduce and use rw_onproc() instead of abusing mutex_onproc().
- Change the handoff/release algorithm to reduce the window when a rwlock
  can held, but the owner not on a CPU.


To generate a diff of this commit:
cvs rdiff -r1.19 -r1.20 src/sys/kern/kern_rwlock.c
cvs rdiff -r1.4 -r1.5 src/sys/sys/rwlock.h

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.