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 using the existing lock in packing_data which is
initialized early in cmd_pack_objects instead of read_mutex.
Additionally, upgrade the packing_data lock to a recursive mutex to
make it a suitable replacement for read_mutex.
Signed-off-by: Patrick Hogg <phogg@xxxxxxxxxxxx>
---
As I mentioned in the prior thread I think that it will be simpler
to simply use the existing lock in packing_data instead of moving
read_mutex. I can go back to simply moving read_mutex to the
packing_data struct if that that is preferable, though.
I also removed the #ifndef NO_PTHREADS in prepare_packing_data around
the initialization of &pdata->lock since I had to upgrade the lock to
a recursive mutex. As far as I can tell init_recursive_mutex (and
pthread_mutex_init for that matter) have that protection already so it
appears to be redundant.
builtin/pack-objects.c | 27 ++++++++++++---------------
pack-objects.c | 4 +---
2 files changed, 13 insertions(+), 18 deletions(-)
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 411aefd68..5439b434c 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1954,9 +1954,8 @@ static int delta_cacheable(unsigned long src_size, unsigned long trg_size,
}
/* Protect access to object database */
-static pthread_mutex_t read_mutex;
-#define read_lock() pthread_mutex_lock(&read_mutex)
-#define read_unlock() pthread_mutex_unlock(&read_mutex)
+#define pack_lock() packing_data_lock(&to_pack)
+#define pack_unlock() packing_data_unlock(&to_pack)
/* Protect delta_cache_size */
static pthread_mutex_t cache_mutex;
@@ -1993,11 +1992,11 @@ unsigned long oe_get_size_slow(struct packing_data *pack,
unsigned long used, avail, size;
if (e->type_ != OBJ_OFS_DELTA && e->type_ != OBJ_REF_DELTA) {
- read_lock();
+ pack_lock();
if (oid_object_info(the_repository, &e->idx.oid, &size) < 0)
die(_("unable to get size of %s"),
oid_to_hex(&e->idx.oid));
- read_unlock();
+ pack_unlock();
return size;
}
@@ -2005,7 +2004,7 @@ unsigned long oe_get_size_slow(struct packing_data *pack,
if (!p)
BUG("when e->type is a delta, it must belong to a pack");
- read_lock();
+ pack_lock();
w_curs = NULL;
buf = use_pack(p, &w_curs, e->in_pack_offset, &avail);
used = unpack_object_header_buffer(buf, avail, &type, &size);
@@ -2014,7 +2013,7 @@ unsigned long oe_get_size_slow(struct packing_data *pack,
oid_to_hex(&e->idx.oid));
unuse_pack(&w_curs);
- read_unlock();
+ pack_unlock();
return size;
}
@@ -2076,9 +2075,9 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
/* Load data if not already done */
if (!trg->data) {
- read_lock();
+ pack_lock();
trg->data = read_object_file(&trg_entry->idx.oid, &type, &sz);
- read_unlock();
+ pack_unlock();
if (!trg->data)
die(_("object %s cannot be read"),
oid_to_hex(&trg_entry->idx.oid));
@@ -2089,9 +2088,9 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
*mem_usage += sz;
}
if (!src->data) {
- read_lock();
+ pack_lock();
src->data = read_object_file(&src_entry->idx.oid, &type, &sz);
- read_unlock();
+ pack_unlock();
if (!src->data) {
if (src_entry->preferred_base) {
static int warned = 0;
@@ -2337,9 +2336,9 @@ static void find_deltas(struct object_entry **list, unsigned *list_size,
static void try_to_free_from_threads(size_t size)
{
- read_lock();
+ pack_lock();
release_pack_memory(size);
- read_unlock();
+ pack_unlock();
}
static try_to_free_t old_try_to_free_routine;
@@ -2381,7 +2380,6 @@ static pthread_cond_t progress_cond;
*/
static void init_threaded_search(void)
{
- init_recursive_mutex(&read_mutex);
pthread_mutex_init(&cache_mutex, NULL);
pthread_mutex_init(&progress_mutex, NULL);
pthread_cond_init(&progress_cond, NULL);
@@ -2392,7 +2390,6 @@ static void cleanup_threaded_search(void)
{
set_try_to_free_routine(old_try_to_free_routine);
pthread_cond_destroy(&progress_cond);
- pthread_mutex_destroy(&read_mutex);
pthread_mutex_destroy(&cache_mutex);
pthread_mutex_destroy(&progress_mutex);
}
diff --git a/pack-objects.c b/pack-objects.c
index b6cdbb016..6f32a7ba0 100644
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -148,9 +148,7 @@ void prepare_packing_data(struct packing_data *pdata)
1U << OE_SIZE_BITS);
pdata->oe_delta_size_limit = git_env_ulong("GIT_TEST_OE_DELTA_SIZE",
1UL << OE_DELTA_SIZE_BITS);
-#ifndef NO_PTHREADS
- pthread_mutex_init(&pdata->lock, NULL);
-#endif
+ init_recursive_mutex(&pdata->lock);
}
struct object_entry *packlist_alloc(struct packing_data *pdata,
--
2.20.1.windows.1
