On Wednesday, January 22, 2014 3:59:37 pm Alfred Perlstein wrote: > > On 1/22/14, 12:27 PM, John Baldwin wrote: > > On Wednesday, January 22, 2014 2:06:39 pm Alfred Perlstein wrote: > >> Hmm, what if locks had a pointer to a 2 element char * array, the first > >> being the name, the second the type. That would keep the size of the > >> lock down and most locks could share a common tuple of name/type in each > >> subsystem. This would allow us to get rid of the pending static list. > >> > >> effectively: > >> struct lock_object { > >> char *lo_name; /* Individual lock name. */ > >> u_int lo_flags; > >> u_int lo_data; /* General class specific data. */ > >> struct witness *lo_witness; /* Data for witness. */ > >> }; > >> > >> would change to: > >> struct lock_object { > >> char **lo_name_type; /* Individual lock > >> name[0]/type[1]. */ > >> u_int lo_flags; > >> u_int lo_data; /* General class specific data. */ > >> struct witness *lo_witness; /* Data for witness. */ > >> }; > >> > >> This may be somewhat disruptive, I haven't played with how it would > >> actually change driver/etc/code. > > Where would the memory for the char* array come from? > > > That is a good question. I suspect it would be up to the subsystem to > allocate it. > > Wouldn't it be trivial for *most* of the subsystems to simply have this > either as a static global or static function variable: > > static char *mutex_typename = { "kqueue", "foo" }; > > Under kern I see this: > grep mtx_init * | grep -v NULL > ... > kern_rmlock.c: mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx", > MTX_NOWITNESS); > subr_bus.c: mtx_init(&devsoftc.mtx, "dev mtx", "devd", MTX_DEF); > > Those are solved with statics. > > Another example: > > sys/dev/ae/if_ae.c > mtx_init(&sc->mtx, device_get_nameunit(dev), MTX_NETWORK_LOCK, > MTX_DEF); > > I think the array could be in the softc here? sc->mutex_name_type[0] = > device_get_nameunit(dev); sc->mutex_name_type[1] = MTX_NETWORK_LOCK; > > Do we want to do that? It moves "wasting space" to another variable. > > I'm not sure where there isn't the possibility of using either static > (for a global mutex) or space inside the equiv of the softc (or proc or > whatever) for this? > > I'm not sure this is a good idea, just an idea. Are there places where > it's not as simple as doing this?
To be honest, the whole name vs type thing isn't widely used, and it makes the mtx_init() function kind of fugly. I think what I would actually prefer is to just kill it, changing the various places that pass a separate name to just pass the type instead. Note that none of the other lock APIs even allow setting a separate type. This would let us remove the static pending list array as well. (And yes, I added the name vs type thing, but at this point I think it did not turn out nearly as useful as I had thought it would be.) The original issue of picking useful-to-witness lock names (i.e. not just using device_get_nameunit()) still remains of course. -- 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"