tree ca6a17268d9e88b6bcd4b880177123877a49e95a
parent 87615097835bce8ac687e8d7f1993d25f585afab
author Kaushik Lingarkar <klingarkar@nvidia.com> 1787350558 -0700
committer Kaushik Lingarkar <klingarkar@nvidia.com> 1787354939 -0700

PackedBatchRefUpdate: Release locks in reverse order of acquisition

PackedBatchRefUpdate#execute takes three locks on the way in. First the
in-process packed-refs lock, then the loose ref locks, and last is the
packed-refs lock file. On the way out it unlocked them in a different
order, the loose refs, then the packed-refs lock file, then the
in-process lock.

This change gives each lock its own finally block, scoped to the region
where it is actually held. Every lock is now unlocked in the reverse of
the order it was locked. And no path can slip past an unlock, since a
failure to release one lock still leaves the enclosing finally blocks to
release the others. Before this, a failure while unlocking the loose
refs would have left the packed-refs lock file behind on disk.

Change-Id: Iac7425f9e4fab666b0c04fc6f153789d24950009
Signed-off-by: Kaushik Lingarkar <klingarkar@nvidia.com>