svn commit: r254703 - in head: share/man/man9 sys/sys

[Davide Italiano]

On Fri, Aug 23, 2013 at 4:51 PM, John Baldwin <jhb at 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?

Thanks,

-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare