From f59bb63746924d44aecc1a0c65902292736360c6 Mon Sep 17 00:00:00 2001
From: "Kyle J. McKay" <mackyle@gmail.com>
Date: Wed, 10 Jun 2020 12:18:11 -0700
Subject: [PATCH] git-svn gc: acquire a `gc.pid` lock for any packing
 activities

It really should not be possible for any kind of gc to run on
an svn mirror project while a clone/update operation is in progress.

It really shouldn't.

Nevertheless, do the right thing and acquire a `gc.pic` lock
for the duration of any packing operations.

Since, strictly speaking, no packing is actually required during
a clone or update of a `git-svn` mirror, failure to acquire
the lock only results in the packing operation being skipped
rather than an outright failure.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
---
 jobd/gc-git-svn.sh        |  7 +++++--
 jobd/gc-util-functions.sh | 18 +++++++++++++++++-
 taskd/clone.sh            |  3 ++-
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/jobd/gc-git-svn.sh b/jobd/gc-git-svn.sh
index 1dbecc2..15397cc 100755
--- a/jobd/gc-git-svn.sh
+++ b/jobd/gc-git-svn.sh
@@ -34,8 +34,11 @@ proj="${proj%.git}"
 
 if lotsa_loose_pruned_objects; then
 	echo "Packing loose objects ($(date))"
-	pack_incremental_loose_objects
-	echo "Packing and pruning complete ($(date))"
+	if pack_incremental_loose_objects_if_lockable; then
+		echo "Packing and pruning complete ($(date))"
+	else
+		echo "Packing skipped: $lockerr ($(date))"
+	fi
 fi
 
 exit 0
diff --git a/jobd/gc-util-functions.sh b/jobd/gc-util-functions.sh
index 7feb14f..66952c2 100755
--- a/jobd/gc-util-functions.sh
+++ b/jobd/gc-util-functions.sh
@@ -163,10 +163,12 @@ lotsa_loose_objects() {
 	[ ${_objs:-0} -ge 5 ]
 }
 
-# same as lotsa_loose_objects but first runs `git prune-packed`
+# same as lotsa_loose_objects but first runs `git prune-packed` if it can get a gc lock
 lotsa_loose_pruned_objects() {
 	lotsa_loose_objects || return $?
+	v_lock_gc _gclock || return 0
 	git prune-packed --quiet
+	rm -f "$_gclock"
 	lotsa_loose_objects
 }
 
@@ -195,6 +197,20 @@ pack_incremental_loose_objects() {
 	}
 }
 
+# same as pack_incremental_loose_objects except
+# returns true if locked and packed and unlocked or
+# false if could not lock (with err in $lockerr)
+pack_incremental_loose_objects_if_lockable() {
+	if v_lock_gc _gclock; then
+		pack_incremental_loose_objects || :
+		rm -f "$_gclock"
+		return 0
+	else
+		lockerr="$_gclock"
+		return 1
+	fi
+}
+
 # combine small _l packs into larger pack(s) using --weak-naming
 # we avoid any non _l, keep, bndl or bitmap packs
 combine_small_incremental_loose_packs() {
diff --git a/taskd/clone.sh b/taskd/clone.sh
index 44646d6..a91f868 100755
--- a/taskd/clone.sh
+++ b/taskd/clone.sh
@@ -405,7 +405,8 @@ case "$url" in
 			else
 				pausestop="$(( $(date '+%s') + 120 ))"
 				echo 'Pausing and packing loose objects for 120 seconds before retrying'
-				pack_incremental_loose_objects
+				pack_incremental_loose_objects_if_lockable ||
+				echo "Packing skipped: $lockerr"
 				timenow="$(date '+%s')"
 				if [ "$timenow" -lt "$pausestop" ]; then
 					sleepamt="$(( $pausestop - $timenow ))"
-- 
2.11.4.GIT