CVSROOT: /cvs
Module name: src
Changes by: mi...@cvs.openbsd.org 2016/01/26 08:51:07
Modified files:
sys/dev/pv : xen.c
Log message:
No need to take a grant table entry mutex in xen_grant_table_{enter,remove}
Grant table API is constructed in a way that once allocated grant table
entries are marked as used and cannot be given away again to some other
user. At the same time xen_grant_table_enter and _remove do not operate
on the same grant reference at the same time, so there's no need for a
lock here. Guard flag operations with memory fences to ensure correct
store/load order. This provides some decent performance improvement as
well.
