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Merge branch 'jk/index-pack-threading-races'

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When receiving an invalid pack stream that records the same object
twice, multiple threads got confused due to a race.  We should
reject or correct such a stream upon receiving, but that will be a
larger change.

* jk/index-pack-threading-races:
  index-pack: fix race condition with duplicate bases
This commit is contained in:
Junio C Hamano 2014-09-19 11:38:33 -07:00
commit bd656f6e7b
1 changed files with 31 additions and 2 deletions
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33
builtin/index-pack.c
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@ -112,6 +112,10 @@ static pthread_mutex_t deepest_delta_mutex;
#define deepest_delta_lock() lock_mutex(&deepest_delta_mutex)
#define deepest_delta_unlock() unlock_mutex(&deepest_delta_mutex)
static pthread_mutex_t type_cas_mutex;
#define type_cas_lock() lock_mutex(&type_cas_mutex)
#define type_cas_unlock() unlock_mutex(&type_cas_mutex)
static pthread_key_t key;
static inline void lock_mutex(pthread_mutex_t *mutex)
@ -135,6 +139,7 @@ static void init_thread(void)
init_recursive_mutex(&read_mutex);
pthread_mutex_init(&counter_mutex, NULL);
pthread_mutex_init(&work_mutex, NULL);
pthread_mutex_init(&type_cas_mutex, NULL);
if (show_stat)
pthread_mutex_init(&deepest_delta_mutex, NULL);
pthread_key_create(&key, NULL);
@ -157,6 +162,7 @@ static void cleanup_thread(void)
pthread_mutex_destroy(&read_mutex);
pthread_mutex_destroy(&counter_mutex);
pthread_mutex_destroy(&work_mutex);
pthread_mutex_destroy(&type_cas_mutex);
if (show_stat)
pthread_mutex_destroy(&deepest_delta_mutex);
for (i = 0; i < nr_threads; i++)
@ -862,7 +868,6 @@ static void resolve_delta(struct object_entry *delta_obj,
{
void *base_data, *delta_data;
delta_obj->real_type = base->obj->real_type;
if (show_stat) {
delta_obj->delta_depth = base->obj->delta_depth + 1;
deepest_delta_lock();
@ -888,6 +893,26 @@ static void resolve_delta(struct object_entry *delta_obj,
counter_unlock();
}
/*
* Standard boolean compare-and-swap: atomically check whether "*type" is
* "want"; if so, swap in "set" and return true. Otherwise, leave it untouched
* and return false.
*/
static int compare_and_swap_type(enum object_type *type,
enum object_type want,
enum object_type set)
{
enum object_type old;
type_cas_lock();
old = *type;
if (old == want)
*type = set;
type_cas_unlock();
return old == want;
}
static struct base_data *find_unresolved_deltas_1(struct base_data *base,
struct base_data *prev_base)
{
@ -915,7 +940,10 @@ static struct base_data *find_unresolved_deltas_1(struct base_data *base,
struct object_entry *child = objects + deltas[base->ref_first].obj_no;
struct base_data *result = alloc_base_data();
assert(child->real_type == OBJ_REF_DELTA);
if (!compare_and_swap_type(&child->real_type, OBJ_REF_DELTA,
base->obj->real_type))
die("BUG: child->real_type != OBJ_REF_DELTA");
resolve_delta(child, base, result);
if (base->ref_first == base->ref_last && base->ofs_last == -1)
free_base_data(base);
@ -929,6 +957,7 @@ static struct base_data *find_unresolved_deltas_1(struct base_data *base,
struct base_data *result = alloc_base_data();
assert(child->real_type == OBJ_OFS_DELTA);
child->real_type = base->obj->real_type;
resolve_delta(child, base, result);
if (base->ofs_first == base->ofs_last)
free_base_data(base);