On Friday, August 23, 2013 11:29:45 am Davide Italiano wrote: > On Fri, Aug 23, 2013 at 4:51 PM, John Baldwin <j...@freebsd.org> wrote: > > On Friday, August 23, 2013 10:12:39 am Davide Italiano wrote: > >> Author: davide > >> Date: Fri Aug 23 14:12:39 2013 > >> New Revision: 254703 > >> URL: http://svnweb.freebsd.org/changeset/base/254703 > >> > >> Log: > >> Introduce callout_init_rm() so that callouts can be used in conjunction > >> with rmlocks. This works only with non-sleepable rm because handlers run > >> in SWI context. While here, document the new KPI in the timeout(9) > >> manpage. > > > > It also only works with exclusive locks. (lc_unlock/lc_lock only handle > > write locks for rmlocks). > > > > -- > > John Baldwin > > Thanks for pointing out this. > I think it would be nice to have lc_lock/lc_unlock working both for > shared and exclusive locks but I'm not 100% sure about all the > implications/complications. From what I see for rwlocks asserting if a > lock is held in read-mode is really cheap (check against a flag) while > for rmlocks the assertion relies on traversing the tracker list for > the rmlock so I'm worried this operation could be expensive. What's > your opinion about?
The much bigger problem is you need an rmtracker object to pass to the lock/unlock routines. You could make this work hackishly in the callout case by special casing rm locks that use read locking and using a tracker on softclock's stack, but it is much harder to fix this for the rm_sleep() case where the sequence is lc_unlock/lc_lock. -- John Baldwin _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
