K 10
svn:author
V 7
iedowse
K 8
svn:date
V 27
2005-03-21T23:01:30.000000Z
K 7
svn:log
V 767
Partialially MFC the changes to the callout system that prevent
race conditions when stopping and resetting timers. This only avoids
the race conditions with Giant-locked callouts; it was not possible
to backport callout_init_mtx() since adding the c_mtx field to
struct callout would have changed the callout ABI.

Giant-locked callouts will now have much simpler semantics. As long
as Giant is held when invoking callout_stop() or callout_reset(),
then these functions will guarantee that the callout will be stopped,
even if softclock() had already begun to process the callout.

There should be no change in behaviour for "MP-safe" callouts; these
still need to use the techniques now described in timeout(9) to
avoid race conditions.

Approved by:	re (kensmith)

END