CVS commit: src/sys/kern

["Jaromir Dolecek" <jdolecek%netbsd.org@localhost>]

Module Name:    src
Committed By:   jdolecek
Date:           Wed Jan 20 21:39:09 UTC 2021

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

Log Message:
fix a race in kqueue_scan() - when multiple threads check the same
kqueue, it could happen other thread seen empty kqueue while kevent
was being checked for re-firing and re-queued

make sure to keep retrying if there are outstanding kevents even
if no kevent is found on first pass through the queue, and only
drop the KN_QUEUED flag and kq_count when actually completely done
with the kevent

change is inspired by the FreeBSD in-flux handling, but without
introducing the reference counting

PR kern/50094 by Christof Meerwald


To generate a diff of this commit:
cvs rdiff -u -r1.110 -r1.111 src/sys/kern/kern_event.c

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