pack-objects: move read mutex to packing_data struct

ac77d0c37 ("pack-objects: shrink size field in struct object_entry",
2018-04-14) added an extra usage of read_lock/read_unlock in the newly
introduced oe_get_size_slow for thread safety in parallel calls to
try_delta(). Unfortunately oe_get_size_slow is also used in serial
code, some of which is called before the first invocation of
ll_find_deltas. As such the read mutex is not guaranteed to be
initialized.

Resolve this by moving the read mutex to packing_data and initializing
it in prepare_packing_data which is initialized in cmd_pack_objects.

Signed-off-by: Patrick Hogg <phogg@novamoon.net>
Reviewed-by: Duy Nguyen <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/pack-objects.h b/pack-objects.h
index dc869f2..0a038e3 100644
--- a/pack-objects.h
+++ b/pack-objects.h
@@ -146,6 +146,7 @@ struct packing_data {
 	struct packed_git **in_pack;
 
 	pthread_mutex_t lock;
+	pthread_mutex_t read_lock;
 
 	/*
 	 * This list contains entries for bases which we know the other side
@@ -174,6 +175,15 @@ static inline void packing_data_unlock(struct packing_data *pdata)
 	pthread_mutex_unlock(&pdata->lock);
 }
 
+static inline void packing_data_read_lock(struct packing_data *pdata)
+{
+	pthread_mutex_lock(&pdata->read_lock);
+}
+static inline void packing_data_read_unlock(struct packing_data *pdata)
+{
+	pthread_mutex_unlock(&pdata->read_lock);
+}
+
 struct object_entry *packlist_alloc(struct packing_data *pdata,
 				    const unsigned char *sha1,
 				    uint32_t index_pos);