On Fri, Oct 13, 2017 at 10:36:26PM -0700, Matt Joras wrote:
> On 10/13/2017 22:12, Ngie Cooper (yaneurabeya) wrote:
> >> Modified: head/sys/kern/subr_unit.c
> >> ==============================================================================
> >> --- head/sys/kern/subr_unit.c Wed Oct 11 20:36:22 2017
> >> (r324540)
> >> +++ head/sys/kern/subr_unit.c Wed Oct 11 21:53:50 2017
> >> (r324541)
> >> @@ -366,6 +366,27 @@ delete_unrhdr(struct unrhdr *uh)
> >> Free(uh);
> >> }
> >>
> >> +void
> >> +clear_unrhdr(struct unrhdr *uh)
> >> +{
> >> + struct unr *up, *uq;
> >> +
> >> + KASSERT(TAILQ_EMPTY(&uh->ppfree),
> >> + ("unrhdr has postponed item for free"));
> >> + up = TAILQ_FIRST(&uh->head);
> >> + while (up != NULL) {
> > Could this be done with TAILQ_FOREACH_SAFE?
> > -Ngie
>
>
> Yes but it is arguably inferior to do so. This while loop is
> theoretically faster since there is no need to individually remove the
> elements when you intend to delete every element.
TAILQ_FOREACH_SAFE just fetches the next element at the beginning of
each loop iteration rather than at the end, same as the current
implementation of clear_unrhdr() does. There's no change to the code
generated by clang when I replace your loop with:
TAILQ_FOREACH_SAFE(up, &uh->head, list, uq) {
if (up->ptr != uh) {
Free(up->ptr);
}
Free(up);
}
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