[PATCH 06/11] git-fetch: Release objects used by a prior transport

[PATCH 06/11] git-fetch: Release objects used by a prior transport

[Shawn O. Pearce]

Some transports allocate objects in the internal object hashtable
during the fetch process (e.g. the HTTP commit walker and also the
native protocol).  These shouldn't be visible to another transport
call running in the same fetch process when we fetch the tags during
automated tag following.  By deallocating the object table (if it
has anything in it) we ensure the second transport execution will
be from a clean slate.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
 builtin-fetch.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/builtin-fetch.c b/builtin-fetch.c
index 847db73..18f123e 100644
--- a/builtin-fetch.c
+++ b/builtin-fetch.c
@@ -337,7 +337,10 @@ static void store_updated_refs(const char *url, struct ref *ref_map)
 
 static int fetch_refs(struct transport *transport, struct ref *ref_map)
 {
-	int ret = transport_fetch_refs(transport, ref_map);
+	int ret;
+
+	free_all_objects();
+	ret = transport_fetch_refs(transport, ref_map);
 	if (!ret)
 		store_updated_refs(transport->url, ref_map);
 	transport_unlock_pack(transport);
-- 
1.5.3.5.1622.g41d10

Re: [PATCH 06/11] git-fetch: Release objects used by a prior transport

[Junio C Hamano]

"Shawn O. Pearce" <spearce@spearce.org> writes:

> Some transports allocate objects in the internal object hashtable
> during the fetch process (e.g. the HTTP commit walker and also the
> native protocol).  These shouldn't be visible to another transport
> call running in the same fetch process when we fetch the tags during
> automated tag following.  By deallocating the object table (if it
> has anything in it) we ensure the second transport execution will
> be from a clean slate.
>
> Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
> ---
>  builtin-fetch.c |    5 ++++-
>  1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/builtin-fetch.c b/builtin-fetch.c
> index 847db73..18f123e 100644
> --- a/builtin-fetch.c
> +++ b/builtin-fetch.c
> @@ -337,7 +337,10 @@ static void store_updated_refs(const char *url, struct ref *ref_map)
>  
>  static int fetch_refs(struct transport *transport, struct ref *ref_map)
>  {
> -	int ret = transport_fetch_refs(transport, ref_map);
> +	int ret;
> +
> +	free_all_objects();
> +	ret = transport_fetch_refs(transport, ref_map);
>  	if (!ret)
>  		store_updated_refs(transport->url, ref_map);
>  	transport_unlock_pack(transport);

This sounds a very heavy-handed approach.

Is it the callers responsibility to know what function does call
free_all_objects() and makes sure there is no pointer to objects
obtained before the call that is used after the call returns?

Re: [PATCH 06/11] git-fetch: Release objects used by a prior transport

[Shawn O. Pearce]

Junio C Hamano <gitster@pobox.com> wrote:
> "Shawn O. Pearce" <spearce@spearce.org> writes:
> > diff --git a/builtin-fetch.c b/builtin-fetch.c
> > index 847db73..18f123e 100644
> > --- a/builtin-fetch.c
> > +++ b/builtin-fetch.c
> > @@ -337,7 +337,10 @@ static void store_updated_refs(const char *url, struct ref *ref_map)
> >  
> >  static int fetch_refs(struct transport *transport, struct ref *ref_map)
> >  {
> > -	int ret = transport_fetch_refs(transport, ref_map);
> > +	int ret;
> > +
> > +	free_all_objects();
> > +	ret = transport_fetch_refs(transport, ref_map);
> >  	if (!ret)
> >  		store_updated_refs(transport->url, ref_map);
> >  	transport_unlock_pack(transport);
> 
> This sounds a very heavy-handed approach.
> 
> Is it the callers responsibility to know what function does call
> free_all_objects() and makes sure there is no pointer to objects
> obtained before the call that is used after the call returns?

Yea, I guess it is.  That's part of the reason why this usage was
put here in a static function of builtin-fetch.  Its high enough
up in the call stack that nobody above it cares.  Where we would
run into trouble would be if a transport decided to hang onto any
pointers in its data structure between calls to the transport.

Lets just say we don't free the objects; the flags are still all
messed up from any prior user.  Its tricky to reuse the objects
because we don't know what state an object is left in by someone
that ran before us (e.g. an internal call to fetch-pack!).  Its
also tricky when they free the parent list but leave parsed=1;
we can't rebuild the parent pointers!

-- 
Shawn.