CVS commit: src/sys/kern

[Chris Gilbert <chris%netbsd.org@localhost>]

Module Name:    src
Committed By:   chris
Date:           Sun Jun 15 09:56:18 UTC 2008

Modified Files:
        src/sys/kern: kern_condvar.c

Log Message:
Fix for biowait hangs, and possibly other condvar hangs.  Also should fix
PR kern/38761.

The condvar must access the sleepq with the sleepq lock held, doing so
is causing inconsistent sleepq state to be read.

This is because some accesses to the sleepq don't come via the cv code,
but are call directly into sleepq_changepri and sleepq_lendpri, which take
the sleepq lock, and removes then re-inserts lwps into the sleepq.

Running a build.sh with -j8 now completes on my quad-core, also tested by
Simon@ on a 8-core server and matt@ on a quad-core.

I believe there is room to be more efficient with this, as we now take the
sleepq lock for all cv_broadcast and cv_signal calls. I'll look into this
and post a diff to tech-kern.


To generate a diff of this commit:
cvs rdiff -r1.22 -r1.23 src/sys/kern/kern_condvar.c

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