Re: [PATCH 1/2] merge: close the index lock when not writing the new index

[Martin Ågren]

On 11 November 2017 at 00:13, Joel Teichroeb  wrote:
> If the merge does not have anything to do, it does not unlock the index,
> causing any further index operations to fail. Thus, always unlock the index
> regardless of outcome.

> if (clean < 0)
> return clean;

Do we need to roll back the lock also if `clean` is negative? The
current callers are built-ins which will error out, but future callers
might be caught off guard by this.

> -   if (active_cache_changed &&
> -   write_locked_index(&the_index, &lock, COMMIT_LOCK))
> -   return err(o, _("Unable to write index."));
> +   if (active_cache_changed) {
> +   if (write_locked_index(&the_index, &lock, COMMIT_LOCK))
> +   return err(o, _("Unable to write index."));
> +   } else {
> +   rollback_lock_file(&lock);
> +   }
>
> return clean ? 0 : 1;
>  }

Looks correct. A simpler change which would still match the commit
message would be to unconditionally call `rollback_lock_file()` just
before returning. That would perhaps be slightly more future-proof,
since it will always leave the lock unlocked, even if the if-else grows
more complicated.

Well, "always" modulo returning early and forgetting to roll back the
lock. ;-) Looking at existing code, it's not obvious which way we should
prefer. Just a thought.

Thanks for spotting this. I was poking around here recently, but failed
to notice this lax lock-handling.

Martin

[PATCH 1/2] merge: close the index lock when not writing the new index

[Joel Teichroeb]

If the merge does not have anything to do, it does not unlock the index,
causing any further index operations to fail. Thus, always unlock the index
regardless of outcome.

Signed-off-by: Joel Teichroeb 
---
 merge-recursive.c | 9 ++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/merge-recursive.c b/merge-recursive.c
index 2ca8444c6..225ff3fb5 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -2184,9 +2184,12 @@ int merge_recursive_generic(struct merge_options *o,
if (clean < 0)
return clean;
 
-   if (active_cache_changed &&
-   write_locked_index(&the_index, &lock, COMMIT_LOCK))
-   return err(o, _("Unable to write index."));
+   if (active_cache_changed) {
+   if (write_locked_index(&the_index, &lock, COMMIT_LOCK))
+   return err(o, _("Unable to write index."));
+   } else {
+   rollback_lock_file(&lock);
+   }
 
return clean ? 0 : 1;
 }
-- 
2.15.0