On Wed, Mar 31, 2021 at 1:32 AM Christian Couder
<christian.couder@xxxxxxxxx> wrote:
>
> On Wed, Mar 17, 2021 at 10:12 PM Matheus Tavares
> <matheus.bernardino@xxxxxx> wrote:
>
> > diff --git a/.gitignore b/.gitignore
> > index 3dcdb6bb5a..26f8ddfc55 100644
> > --- a/.gitignore
> > +++ b/.gitignore
> > @@ -33,6 +33,7 @@
> > /git-check-mailmap
> > /git-check-ref-format
> > /git-checkout
> > +/git-checkout--helper
>
> I wonder if "checkout--worker" would be better than "checkout--helper".
Yeah, good idea, I'll change that.
> > /git-checkout-index
> > /git-cherry
> > /git-cherry-pick
>
> [...]
>
> > +#define ASSERT_PC_ITEM_RESULT_SIZE(got, exp) \
> > +{ \
> > + if (got != exp) \
> > + BUG("corrupted result from checkout worker (got %dB, exp %dB)", \
>
> Maybe precompilers are smart enough to not replace the "got" and "exp"
> in the above string, but it might be a bit confusing for readers.
> Anway I wonder if this macro could just be a regular (possibly inline)
> function.
Ok, I will replace this with an inline function.
> > + got, exp); \
> > +} while(0)
>
> > +static void parse_and_save_result(const char *line, int len,
> > + struct pc_worker *worker)
> > +{
> > + struct pc_item_result *res;
> > + struct parallel_checkout_item *pc_item;
> > + struct stat *st = NULL;
> > +
> > + if (len < PC_ITEM_RESULT_BASE_SIZE)
> > + BUG("too short result from checkout worker (got %dB, exp %dB)",
> > + len, (int)PC_ITEM_RESULT_BASE_SIZE);
> > +
> > + res = (struct pc_item_result *)line;
> > +
> > + /*
> > + * Worker should send either the full result struct on success, or
> > + * just the base (i.e. no stat data), otherwise.
> > + */
> > + if (res->status == PC_ITEM_WRITTEN) {
> > + ASSERT_PC_ITEM_RESULT_SIZE(len, (int)sizeof(struct pc_item_result));
> > + st = &res->st;
> > + } else {
> > + ASSERT_PC_ITEM_RESULT_SIZE(len, (int)PC_ITEM_RESULT_BASE_SIZE);
> > + }
> > +
> > + if (!worker->nr_items_to_complete || res->id != worker->next_item_to_complete)
>
> Nit: maybe it could be useful to distinguish between these 2 potential
> bugs and have a specific BUG() for each one.
Right, will do.
> > +static void gather_results_from_workers(struct pc_worker *workers,
> > + int num_workers)
> > +{
> > + int i, active_workers = num_workers;
> > + struct pollfd *pfds;
> > +
> > + CALLOC_ARRAY(pfds, num_workers);
> > + for (i = 0; i < num_workers; i++) {
> > + pfds[i].fd = workers[i].cp.out;
> > + pfds[i].events = POLLIN;
> > + }
> > +
> > + while (active_workers) {
> > + int nr = poll(pfds, num_workers, -1);
> > +
> > + if (nr < 0) {
> > + if (errno == EINTR)
> > + continue;
> > + die_errno("failed to poll checkout workers");
> > + }
> > +
> > + for (i = 0; i < num_workers && nr > 0; i++) {
>
> Is it possible that nr is 0? If that happens, it looks like we would
> be in an infinite `while (active_workers) { ... }` loop.
>
> Actually in poll(2) there is: "A value of 0 indicates that the call
> timed out and no file descriptors were ready." So it seems that it
> could, at least theorically, happen.
I think a 0 return might not be possible in this case because we call
poll() with -1 as the timeout, which means "infinite timeout". So the
call should block until either an error occurs (negative return code)
or there is a file descriptor available for reading (positive return
code).
> > +enum pc_item_status {
> > + PC_ITEM_PENDING = 0,
> > + PC_ITEM_WRITTEN,
> > + /*
> > + * The entry could not be written because there was another file
> > + * already present in its path or leading directories. Since
> > + * checkout_entry_ca() removes such files from the working tree before
> > + * enqueueing the entry for parallel checkout, it means that there was
> > + * a path collision among the entries being written.
> > + */
> > + PC_ITEM_COLLIDED,
> > + PC_ITEM_FAILED,
> > +};
> > +
> > +struct parallel_checkout_item {
> > + /*
> > + * In main process ce points to a istate->cache[] entry. Thus, it's not
> > + * owned by us. In workers they own the memory, which *must be* released.
> > + */
> > + struct cache_entry *ce;
> > + struct conv_attrs ca;
> > + size_t id; /* position in parallel_checkout.items[] of main process */
> > +
> > + /* Output fields, sent from workers. */
> > + enum pc_item_status status;
> > + struct stat st;
> > +};
>
> Maybe the previous patch could have declared both 'enum
> pc_item_status' and 'struct parallel_checkout_item' here, in
> parallel-checkout.h, so that this patch wouldn't need to move them
> here.
Yeah, while I was writing this patch I went back and forth on whether
to declare these here from the start. But because I wanted to have the
"parallel-checkout users" / "checkout--helper interface" division in
parallel-checkout.h, I thought it would be better to move the structs
to this header only after the checkout--helper was introduced.
