Re: [PATCH 2/6] fetch-pack: truly stop negotiation upon ACK ready
- From
- Jonathan Tan <jonathantanmy@google.com>
- Date
- Jun 6, 2018, 00:38 UTC
- Message-ID
- <20180605173818.4d56cf328d81b29a2878c1f6@google.com>
- In-Reply-To
- <20180605231634.GD9266@aiede.svl.corp.google.com>
On Tue, 5 Jun 2018 16:16:34 -0700 Jonathan Nieder <jrnieder@gmail.com> wrote:
Show 10 quoted lines
> Hi, > > Jonathan Tan wrote: > > > When "ACK %s ready" is received, find_common() clears rev_list in an > > attempt to stop further "have" lines from being sent [1]. This appears > > to work, despite the invocation to mark_common() in the "while" loop. > > Does "appears to work" mean "works" or "doesn't work but does an okay > job of faking"?
"Appears to work" means I think that it works, but I don't think I can conclusively prove it.
Show 17 quoted lines
> > Though it is possible for mark_common() to invoke rev_list_push() (thus > > making rev_list non-empty once more), it is more likely that the commits > > nit: s/more likely/most likely/ > or s/it is more likely that/usually/ > > > in rev_list that have un-SEEN parents are also unparsed, meaning that > > mark_common() is not invoked on them. > > > > To avoid all this uncertainty, it is better to explicitly end the loop > > when "ACK %s ready" is received instead of clearing rev_list. Remove the > > clearing of rev_list and write "if (got_ready) break;" instead. > > I'm still a little curious about whether this can happen in practice > or whether it's just about readability (or whether you didn't figure > out which, which is perfectly fine), but either way it's a good > change.
I tried to figure out which, but concluded that I can't.
I think that in v2's commit message, I'll start with describing the readability aspect.
Show 10 quoted lines
> > @@ -1281,7 +1281,6 @@ static int process_acks(struct packet_reader *reader, struct oidset *common)
> > }
> >
> > if (!strcmp(reader->line, "ready")) {
> > - clear_prio_queue(&rev_list);
> > received_ready = 1;
> > continue;
>
> I'm curious about the lifetime of &rev_list. Does the priority queue
> get freed eventually?No (which potentially causes a problem in the case that fetch-pack is invoked twice), but I fix that in patch 4/6, so I didn't bother addressing it here. I'll add a note about the lifetime of this priority queue in v2.