On Mon, 21 Jan 2008, Johannes Sixt wrote:
> Sergey Vlasov schrieb:
> > When partitioning the work amongst threads, dividing the number of
> > objects by the number of threads may return 0 when there are less
> > objects than threads; this will cause the subsequent code to segfault
> > when accessing list[sub_size-1]. Fix this by ensuring that sub_size
> > is not zero if there is at least one object to process.
> >
> > Signed-off-by: Sergey Vlasov <vsu@xxxxxxxxxxx>
> > ---
> > builtin-pack-objects.c | 3 +++
> > 1 files changed, 3 insertions(+), 0 deletions(-)
> >
> > diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
> > index ec10238..cdf8aae 100644
> > --- a/builtin-pack-objects.c
> > +++ b/builtin-pack-objects.c
> > @@ -1665,6 +1665,9 @@ static void ll_find_deltas(struct object_entry **list, unsigned list_size,
> > for (i = 0; i < delta_search_threads; i++) {
> > unsigned sub_size = list_size / (delta_search_threads - i);
> >
> > + if (sub_size == 0 && list_size >= 1)
> > + sub_size = 1;
> > +
> > p[i].window = window;
> > p[i].depth = depth;
> > p[i].processed = processed;
>
> I think it fits the logic better to include sub_size > 0 in the while loop
> that follows, like so:
>
> /* try to split chunks on "path" boundaries */
> while (0 < sub_size && sub_size < list_size &&
> list[sub_size]->hash &&
> list[sub_size]->hash == list[sub_size-1]->hash)
> sub_size++;
>
> because we explicitly want to allow threads to "work" on zero objects
> (i.e. do nothing at all), but if a thread does get assigned some work,
> then its chunk is extended past the next path boundary. This way you
> collapse two special cases - "zero-sized chunk" and "path boundary" - into
> one.
Exact.
Nicolas
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