CVS commit: [netbsd-8] src/sys

["Martin Husemann" <martin%netbsd.org@localhost>]

Module Name:    src
Committed By:   martin
Date:           Fri Jan 26 15:41:13 UTC 2018

Modified Files:
        src/sys/kern [netbsd-8]: kern_timeout.c
        src/sys/netinet [netbsd-8]: if_arp.c
        src/sys/netinet6 [netbsd-8]: nd6_nbr.c

Log Message:
Pull up following revision(s) (requested by ozaki-r in ticket #511):
        sys/kern/kern_timeout.c: revision 1.54
        sys/netinet6/nd6_nbr.c: revision 1.141
        sys/netinet6/nd6_nbr.c: revision 1.144
        sys/netinet/if_arp.c: revision 1.256
Fix a deadlock on callout_halt of nd6_dad_timer
We must not call callout_halt of nd6_dad_timer with holding nd6_dad_lock because
the lock is taken in nd6_dad_timer. Once softnet_lock goes away, we can pass the
lock to callout_halt, but for now we cannot.
Make DAD destructions (MP-)safe with callout_stop
arp_dad_stoptimer and nd6_dad_stoptimer can be called with or without
softnet_lock held and unfortunately we have no easy way to statically know which.
So it is hard to use callout_halt there.
To address the situation, we use callout_stop to make the code safe. The new
approach copes with the issue by delegating the destruction of a callout to
callout itself, which allows us to not wait the callout to finish. This can be
done thanks to that DAD objects are separated from other data such as ifa.
The approach is suggested by riastradh@
Proposed on tech-kern@ and tech-net@
Sanity-check if interlock is held when it's passed


To generate a diff of this commit:
cvs rdiff -u -r1.52 -r1.52.2.1 src/sys/kern/kern_timeout.c
cvs rdiff -u -r1.250.2.4 -r1.250.2.5 src/sys/netinet/if_arp.c
cvs rdiff -u -r1.138.6.1 -r1.138.6.2 src/sys/netinet6/nd6_nbr.c

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