Re: [PATCH] dn_route: use time_is_before_jiffies(a) to replace "jiffies - a > 0"

[Yu Zhe]

在 2022年07月28日 21:11, Paolo Abeni 写道:

> On Wed, 2022-07-27 at 10:46 +0800, Yu Zhe wrote:
> > time_is_before_jiffies deals with timer wrapping correctly.
> >
> > Signed-off-by: Yu Zhe <yuzhe@xxxxxxxxxxxx>
> > ---
> >   net/decnet/dn_route.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c
> > index 552a53f1d5d0..0a4bed0bc2e3 100644
> > --- a/net/decnet/dn_route.c
> > +++ b/net/decnet/dn_route.c
> > @@ -201,7 +201,7 @@ static void dn_dst_check_expire(struct timer_list *unused)
> >   		}
> >   		spin_unlock(&dn_rt_hash_table[i].lock);
> >   
> > -		if ((jiffies - now) > 0)
> > +		if (time_is_before_jiffies(now))
> Uhmm... it looks like the wrap-around condition can happen only in
> theory: 'now' is initialized just before entering this loop, and we
> will break as soon as jiffies increment. The wrap-around could happen
> only if a single iteration of the loop takes more than LONG_MAX
> jiffies.
>
> If that happens, we have a completely different kind of much more
> serious problem, I think ;)
>
> So this change is mostly for core readability's sake. I personally find
> more readable:
>
> 		if (jiffies != now)

I agree and I will send a v2 patch later.

> Cheers,
>
> Paolo
>
> p.s. given the above I guess this is for the net-next tree, right?
yes

>