2007/3/12, Pawel Jakub Dawidek <[EMAIL PROTECTED]>:
On Mon, Mar 12, 2007 at 03:35:21PM -0400, John Baldwin wrote: > On Monday 12 March 2007 14:56, Pawel Jakub Dawidek wrote: > > On Mon, Mar 12, 2007 at 11:16:23AM -0400, John Baldwin wrote: > > > On Saturday 10 March 2007 15:52, Pawel Jakub Dawidek wrote: > > > > What about something like this: > > > > > > > > #define cv_wait(cv, lock) do { > > > > switch (LO_CLASSINDEX((struct lock_object *)(lock))) { > > > > > > The problem with a cast is you use type checking. Might as well do this: > > > > > > #define cv_wait(cv, lock) _cv_wait((cv), (struct lock_object *)(lock)) > > > > This will skip type checking and my version only cast to provide type > > checking, so when you pass some random variable it will give you an > > error. > > Not really, you may pass some garbage and the LO_CLASSINDEX turns out to be a > mutex. :) You only get a runtime error, not a compile-time one. > Type-checking by the compiler is nice because you get compile-time errors.I'll get compile-time error, because cv_wait_mtx() takes 'struct condvar *' and 'struct mtx *' as arguments. So even if some garbage returns 1, which turns out to be a mutex, call to cv_wait_mtx() will generate compile-time error.
However, it has another kind of problem we were trying to avoid: the first member of the lock you pass should be the struct lock_object. We should not deal on the ordering of members for locks.
But it seems the solution may not be that good if it is not very obvious on a first look. If typeof() thing works, its fine by me, just give me condvar(9) that works with sx(9) locks:)
I think problems with typeof() are 2: 1) It requires a serie of if/else if before to call the cv_wait() (increase of kernel .text, small slowness, etc.) 2) It is GCC dependant (but we have other of it inside the kernel alredy, so this is a minor nit) 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]"
