Date: Sat, 14 Oct 2017 14:03:05 -0400 From: Mark Johnston <markj@FreeBSD.org> To: Matt Joras <mjoras@FreeBSD.org> Cc: "Ngie Cooper (yaneurabeya)" <yaneurabeya@gmail.com>, src-committers <src-committers@freebsd.org>, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r324541 - in head: share/man/man9 sys/kern sys/sys Message-ID: <20171014180305.GA75158@raichu> In-Reply-To: <a8093059-86ed-1582-a8fa-3c9c8800e213@FreeBSD.org> References: <201710112153.v9BLroeR007323@repo.freebsd.org> <365AD758-5761-4BD4-A80E-8EF2EA84EAAA@gmail.com> <a8093059-86ed-1582-a8fa-3c9c8800e213@FreeBSD.org>
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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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