I am not familiar with _nv() (are there examples in the netbsd code base? I searched _nv() in nxr, but did not found anything meaningful.), but if you want to use atomic operations, one possible way is compare-and-swap (CAS). it has stronger guarantee than atomic inc or atomic dec, but also larger overhead.
2016-05-30 13:30 GMT-07:00 Martin Husemann <mar...@duskware.de>: > On Mon, May 30, 2016 at 01:25:34PM -0700, Charles Cui wrote: > > there is one remaining slot. And each of them will increase p_nsem by one > > using atomic_inc, the results are we have 1 slot overused, but the error > is > > never detected. > > You will have to use a _nv() variant and use the return value to > compare that against the limit, then decrement in the error path. > > Martin >
