On Thu, Feb 07 2008, Ingo Molnar wrote: > > * Linus Torvalds <[EMAIL PROTECTED]> wrote: > > > On Thu, 7 Feb 2008, Ingo Molnar wrote: > > > INIT_HLIST_NODE(&rq->hash); > > > RB_CLEAR_NODE(&rq->rb_node); > > > - rq->ioprio = 0; > > > - rq->buffer = NULL; > > > - rq->ref_count = 1; > > > - rq->q = q; > > > - rq->special = NULL; > > > - rq->data_len = 0; > > > - rq->data = NULL; > > > - rq->nr_phys_segments = 0; > > > - rq->sense = NULL; > > > - rq->end_io = NULL; > > > - rq->end_io_data = NULL; > > > - rq->completion_data = NULL; > > > - rq->next_rq = NULL; > > > + rq->completion_data = NULL; > > > + /* rq->elevator_private */ > > > + /* rq->elevator_private2 */ > > > + /* rq->rq_disk */ > > > + /* rq->start_time */ > > > + rq->nr_phys_segments = 0; > > > + /* rq->nr_hw_segments */ > > > + rq->ioprio = 0; > > > + rq->special = NULL; > > > + rq->buffer = NULL; > > ... > > > > Can we please just stop doing these one-by-one assignments, and just do > > something like > > > > memset(rq, 0, sizeof(*rq)); > > rq->q = q; > > rq->ref_count = 1; > > INIT_HLIST_NODE(&rq->hash); > > RB_CLEAR_NODE(&rq->rb_node); > > > > instead? > > > > The memset() is likely faster and smaller than one-by-one assignments > > anyway, even if the one-by-ones can avoid initializing some field or > > there ends up being a double initialization.. > > i definitely agree and do that for all code i write. > > But if someone does item by item initialization for some crazy > performance reason (networking folks tend to have such constructs), it > should be done i think how i've done it in the patch: by systematically > listing _every_ field in the structure, in the same order, and > indicating it clearly when it is not initialized and why.
That assumes that people find the references in two places when adding members to a structure, not very likely (people are lazy!). > and there it already shows that we do not initialize a few other members > that could cause problems later on: > > + rq->data_len = 0; > + /* rq->sense_len */ > + rq->data = NULL; > + rq->sense = NULL; > > why is sense_len not initialized - while data_len is? In any case, these because sense isn't set, when someone sets ->sense they should set sense_len as well. > days the memclear instructions are dirt cheap and we should just always > initialize everything to zero by default, especially if it's almost all > zero-initialized anyway. Completely agree, some of these are just dormant bugs waiting to happen. Clearing everything is the sanest approach. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
