2007/3/10, Pawel Jakub Dawidek <[EMAIL PROTECTED]>:
On Sat, Mar 10, 2007 at 12:44:26PM +0100, Attilio Rao wrote: > 2007/3/9, John Baldwin <[EMAIL PROTECTED]>: > >I don't have a date set for removing msleep(), esp. given it's wide use. > >I would like to remove it and all the spl*() functions in 8.0 if we can > >swing it. > > > >I also have patches to let condition variables work with rwlocks and sx > >locks, but the current implementation results in an API "explosion" > >since each of the cv_*wait*() functions grows a cv_*wait*_rw() version for > >rwlocks and a cv_*waut*_sx() version for use with sx locks. One possibility > >would be to just cast the lock argument to (struct lock_object *) since all > >of our locks have a lock_object as the first member, but then you use having > >the compiler do type checking, and I'm really not willing to give up on > >that. Too easy to have evil bugs that way. I suppose we could use some > >evil macro that used typeof() but that would be very gcc specific? > > > >I guess one other possibility is to standardize on the field name for > >the lock_object, calling it lo_object instead of mtx_object, rw_object, > >sx_object, etc. Anyone else have any ideas? > > What about adding a new function like: > > static __inline struct lock_object * > mtx_export_lc(struct mtx *m) > { > > return (&m->mtx_object); > } > > to be per-interface (so having sx_export_lc() and rw_export_lc() too) > and than using in this way: > > static struct mtx foo_lock; > static struct cv foo_cv; > ... > > mtx_lock(&foo_lock); > ... > cv_wait(&foo_cv, mtx_export_lc(&foo_lock)); > > (obviously using new struct lock_object methods you added for locking/unlocking) > > It sounds reasonable to you?This is ugly. If we really need to provide information about which type of lock we are using, I'd probably prefer cv_wait_<locktype>(). What about something like this: #define cv_wait(cv, lock) do { switch (LO_CLASSINDEX((struct lock_object *)(lock))) { case 1: cv_wait_mtx(cv, lock); break; case 2: cv_wait_sx(cv, lock); break; case 3: cv_wait_rw(cv, lock); break; default: panic("Invalid lock."); } } while (0)
This is exactly what John is trying to avoid. You have however to export cv_wait_*() & friends in the public namespace and at this point you don't need such wrapper. I know it is not so elegant, but the other solutions are uglier. Having a function returning the lock object per-primitive is the most suitable, IMHO. Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ cvs-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/cvs-all To unsubscribe, send any mail to "[EMAIL PROTECTED]"
