git/object.c
Matheus Tavares b1fc9da1c8 replace-object: make replace operations thread-safe
replace-object functions are very close to being thread-safe: the only
current racy section is the lazy initialization at
prepare_replace_object(). The following patches will protect some object
reading operations to be called threaded, but before that, replace
functions must be protected. To do so, add a mutex to struct
raw_object_store and acquire it before lazy initializing the
replace_map. This won't cause any noticeable performance drop as the
mutex will no longer be used after the replace_map is initialized.

Later, when the replace functions are called in parallel, thread
debuggers might point our use of the added replace_map_initialized flag
as a data race. However, as this boolean variable is initialized as
false and it's only updated once, there's no real harm. It's perfectly
fine if the value is updated right after a thread read it in
replace-map.h:lookup_replace_object() (there'll only be a performance
penalty for the affected threads at that moment). We could cease the
debugger warning protecting the variable reading at the said function.
However, this would negatively affect performance for all threads
calling it, at any time, so it's not really worthy since the warning
doesn't represent a real problem. Instead, to make sure we don't get
false positives (at ThreadSanitizer, at least) an entry for the
respective function is added to .tsan-suppressions.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-01-17 13:52:14 -08:00

572 lines
14 KiB
C

#include "cache.h"
#include "object.h"
#include "replace-object.h"
#include "object-store.h"
#include "blob.h"
#include "tree.h"
#include "commit.h"
#include "tag.h"
#include "alloc.h"
#include "packfile.h"
#include "commit-graph.h"
unsigned int get_max_object_index(void)
{
return the_repository->parsed_objects->obj_hash_size;
}
struct object *get_indexed_object(unsigned int idx)
{
return the_repository->parsed_objects->obj_hash[idx];
}
static const char *object_type_strings[] = {
NULL, /* OBJ_NONE = 0 */
"commit", /* OBJ_COMMIT = 1 */
"tree", /* OBJ_TREE = 2 */
"blob", /* OBJ_BLOB = 3 */
"tag", /* OBJ_TAG = 4 */
};
const char *type_name(unsigned int type)
{
if (type >= ARRAY_SIZE(object_type_strings))
return NULL;
return object_type_strings[type];
}
int type_from_string_gently(const char *str, ssize_t len, int gentle)
{
int i;
if (len < 0)
len = strlen(str);
for (i = 1; i < ARRAY_SIZE(object_type_strings); i++)
if (!strncmp(str, object_type_strings[i], len) &&
object_type_strings[i][len] == '\0')
return i;
if (gentle)
return -1;
die(_("invalid object type \"%s\""), str);
}
/*
* Return a numerical hash value between 0 and n-1 for the object with
* the specified sha1. n must be a power of 2. Please note that the
* return value is *not* consistent across computer architectures.
*/
static unsigned int hash_obj(const struct object_id *oid, unsigned int n)
{
return oidhash(oid) & (n - 1);
}
/*
* Insert obj into the hash table hash, which has length size (which
* must be a power of 2). On collisions, simply overflow to the next
* empty bucket.
*/
static void insert_obj_hash(struct object *obj, struct object **hash, unsigned int size)
{
unsigned int j = hash_obj(&obj->oid, size);
while (hash[j]) {
j++;
if (j >= size)
j = 0;
}
hash[j] = obj;
}
/*
* Look up the record for the given sha1 in the hash map stored in
* obj_hash. Return NULL if it was not found.
*/
struct object *lookup_object(struct repository *r, const struct object_id *oid)
{
unsigned int i, first;
struct object *obj;
if (!r->parsed_objects->obj_hash)
return NULL;
first = i = hash_obj(oid, r->parsed_objects->obj_hash_size);
while ((obj = r->parsed_objects->obj_hash[i]) != NULL) {
if (oideq(oid, &obj->oid))
break;
i++;
if (i == r->parsed_objects->obj_hash_size)
i = 0;
}
if (obj && i != first) {
/*
* Move object to where we started to look for it so
* that we do not need to walk the hash table the next
* time we look for it.
*/
SWAP(r->parsed_objects->obj_hash[i],
r->parsed_objects->obj_hash[first]);
}
return obj;
}
/*
* Increase the size of the hash map stored in obj_hash to the next
* power of 2 (but at least 32). Copy the existing values to the new
* hash map.
*/
static void grow_object_hash(struct repository *r)
{
int i;
/*
* Note that this size must always be power-of-2 to match hash_obj
* above.
*/
int new_hash_size = r->parsed_objects->obj_hash_size < 32 ? 32 : 2 * r->parsed_objects->obj_hash_size;
struct object **new_hash;
new_hash = xcalloc(new_hash_size, sizeof(struct object *));
for (i = 0; i < r->parsed_objects->obj_hash_size; i++) {
struct object *obj = r->parsed_objects->obj_hash[i];
if (!obj)
continue;
insert_obj_hash(obj, new_hash, new_hash_size);
}
free(r->parsed_objects->obj_hash);
r->parsed_objects->obj_hash = new_hash;
r->parsed_objects->obj_hash_size = new_hash_size;
}
void *create_object(struct repository *r, const struct object_id *oid, void *o)
{
struct object *obj = o;
obj->parsed = 0;
obj->flags = 0;
oidcpy(&obj->oid, oid);
if (r->parsed_objects->obj_hash_size - 1 <= r->parsed_objects->nr_objs * 2)
grow_object_hash(r);
insert_obj_hash(obj, r->parsed_objects->obj_hash,
r->parsed_objects->obj_hash_size);
r->parsed_objects->nr_objs++;
return obj;
}
void *object_as_type(struct repository *r, struct object *obj, enum object_type type, int quiet)
{
if (obj->type == type)
return obj;
else if (obj->type == OBJ_NONE) {
if (type == OBJ_COMMIT)
init_commit_node(r, (struct commit *) obj);
else
obj->type = type;
return obj;
}
else {
if (!quiet)
error(_("object %s is a %s, not a %s"),
oid_to_hex(&obj->oid),
type_name(obj->type), type_name(type));
return NULL;
}
}
struct object *lookup_unknown_object(const struct object_id *oid)
{
struct object *obj = lookup_object(the_repository, oid);
if (!obj)
obj = create_object(the_repository, oid,
alloc_object_node(the_repository));
return obj;
}
struct object *parse_object_buffer(struct repository *r, const struct object_id *oid, enum object_type type, unsigned long size, void *buffer, int *eaten_p)
{
struct object *obj;
*eaten_p = 0;
obj = NULL;
if (type == OBJ_BLOB) {
struct blob *blob = lookup_blob(r, oid);
if (blob) {
if (parse_blob_buffer(blob, buffer, size))
return NULL;
obj = &blob->object;
}
} else if (type == OBJ_TREE) {
struct tree *tree = lookup_tree(r, oid);
if (tree) {
obj = &tree->object;
if (!tree->buffer)
tree->object.parsed = 0;
if (!tree->object.parsed) {
if (parse_tree_buffer(tree, buffer, size))
return NULL;
*eaten_p = 1;
}
}
} else if (type == OBJ_COMMIT) {
struct commit *commit = lookup_commit(r, oid);
if (commit) {
if (parse_commit_buffer(r, commit, buffer, size, 1))
return NULL;
if (!get_cached_commit_buffer(r, commit, NULL)) {
set_commit_buffer(r, commit, buffer, size);
*eaten_p = 1;
}
obj = &commit->object;
}
} else if (type == OBJ_TAG) {
struct tag *tag = lookup_tag(r, oid);
if (tag) {
if (parse_tag_buffer(r, tag, buffer, size))
return NULL;
obj = &tag->object;
}
} else {
warning(_("object %s has unknown type id %d"), oid_to_hex(oid), type);
obj = NULL;
}
return obj;
}
struct object *parse_object_or_die(const struct object_id *oid,
const char *name)
{
struct object *o = parse_object(the_repository, oid);
if (o)
return o;
die(_("unable to parse object: %s"), name ? name : oid_to_hex(oid));
}
struct object *parse_object(struct repository *r, const struct object_id *oid)
{
unsigned long size;
enum object_type type;
int eaten;
const struct object_id *repl = lookup_replace_object(r, oid);
void *buffer;
struct object *obj;
obj = lookup_object(r, oid);
if (obj && obj->parsed)
return obj;
if ((obj && obj->type == OBJ_BLOB && repo_has_object_file(r, oid)) ||
(!obj && repo_has_object_file(r, oid) &&
oid_object_info(r, oid, NULL) == OBJ_BLOB)) {
if (check_object_signature(repl, NULL, 0, NULL) < 0) {
error(_("hash mismatch %s"), oid_to_hex(oid));
return NULL;
}
parse_blob_buffer(lookup_blob(r, oid), NULL, 0);
return lookup_object(r, oid);
}
buffer = repo_read_object_file(r, oid, &type, &size);
if (buffer) {
if (check_object_signature(repl, buffer, size, type_name(type)) < 0) {
free(buffer);
error(_("hash mismatch %s"), oid_to_hex(repl));
return NULL;
}
obj = parse_object_buffer(r, oid, type, size,
buffer, &eaten);
if (!eaten)
free(buffer);
return obj;
}
return NULL;
}
struct object_list *object_list_insert(struct object *item,
struct object_list **list_p)
{
struct object_list *new_list = xmalloc(sizeof(struct object_list));
new_list->item = item;
new_list->next = *list_p;
*list_p = new_list;
return new_list;
}
int object_list_contains(struct object_list *list, struct object *obj)
{
while (list) {
if (list->item == obj)
return 1;
list = list->next;
}
return 0;
}
/*
* A zero-length string to which object_array_entry::name can be
* initialized without requiring a malloc/free.
*/
static char object_array_slopbuf[1];
void add_object_array_with_path(struct object *obj, const char *name,
struct object_array *array,
unsigned mode, const char *path)
{
unsigned nr = array->nr;
unsigned alloc = array->alloc;
struct object_array_entry *objects = array->objects;
struct object_array_entry *entry;
if (nr >= alloc) {
alloc = (alloc + 32) * 2;
REALLOC_ARRAY(objects, alloc);
array->alloc = alloc;
array->objects = objects;
}
entry = &objects[nr];
entry->item = obj;
if (!name)
entry->name = NULL;
else if (!*name)
/* Use our own empty string instead of allocating one: */
entry->name = object_array_slopbuf;
else
entry->name = xstrdup(name);
entry->mode = mode;
if (path)
entry->path = xstrdup(path);
else
entry->path = NULL;
array->nr = ++nr;
}
void add_object_array(struct object *obj, const char *name, struct object_array *array)
{
add_object_array_with_path(obj, name, array, S_IFINVALID, NULL);
}
/*
* Free all memory associated with an entry; the result is
* in an unspecified state and should not be examined.
*/
static void object_array_release_entry(struct object_array_entry *ent)
{
if (ent->name != object_array_slopbuf)
free(ent->name);
free(ent->path);
}
struct object *object_array_pop(struct object_array *array)
{
struct object *ret;
if (!array->nr)
return NULL;
ret = array->objects[array->nr - 1].item;
object_array_release_entry(&array->objects[array->nr - 1]);
array->nr--;
return ret;
}
void object_array_filter(struct object_array *array,
object_array_each_func_t want, void *cb_data)
{
unsigned nr = array->nr, src, dst;
struct object_array_entry *objects = array->objects;
for (src = dst = 0; src < nr; src++) {
if (want(&objects[src], cb_data)) {
if (src != dst)
objects[dst] = objects[src];
dst++;
} else {
object_array_release_entry(&objects[src]);
}
}
array->nr = dst;
}
void object_array_clear(struct object_array *array)
{
int i;
for (i = 0; i < array->nr; i++)
object_array_release_entry(&array->objects[i]);
FREE_AND_NULL(array->objects);
array->nr = array->alloc = 0;
}
/*
* Return true iff array already contains an entry with name.
*/
static int contains_name(struct object_array *array, const char *name)
{
unsigned nr = array->nr, i;
struct object_array_entry *object = array->objects;
for (i = 0; i < nr; i++, object++)
if (!strcmp(object->name, name))
return 1;
return 0;
}
void object_array_remove_duplicates(struct object_array *array)
{
unsigned nr = array->nr, src;
struct object_array_entry *objects = array->objects;
array->nr = 0;
for (src = 0; src < nr; src++) {
if (!contains_name(array, objects[src].name)) {
if (src != array->nr)
objects[array->nr] = objects[src];
array->nr++;
} else {
object_array_release_entry(&objects[src]);
}
}
}
void clear_object_flags(unsigned flags)
{
int i;
for (i=0; i < the_repository->parsed_objects->obj_hash_size; i++) {
struct object *obj = the_repository->parsed_objects->obj_hash[i];
if (obj)
obj->flags &= ~flags;
}
}
void clear_commit_marks_all(unsigned int flags)
{
int i;
for (i = 0; i < the_repository->parsed_objects->obj_hash_size; i++) {
struct object *obj = the_repository->parsed_objects->obj_hash[i];
if (obj && obj->type == OBJ_COMMIT)
obj->flags &= ~flags;
}
}
struct parsed_object_pool *parsed_object_pool_new(void)
{
struct parsed_object_pool *o = xmalloc(sizeof(*o));
memset(o, 0, sizeof(*o));
o->blob_state = allocate_alloc_state();
o->tree_state = allocate_alloc_state();
o->commit_state = allocate_alloc_state();
o->tag_state = allocate_alloc_state();
o->object_state = allocate_alloc_state();
o->is_shallow = -1;
o->shallow_stat = xcalloc(1, sizeof(*o->shallow_stat));
o->buffer_slab = allocate_commit_buffer_slab();
return o;
}
struct raw_object_store *raw_object_store_new(void)
{
struct raw_object_store *o = xmalloc(sizeof(*o));
memset(o, 0, sizeof(*o));
INIT_LIST_HEAD(&o->packed_git_mru);
hashmap_init(&o->pack_map, pack_map_entry_cmp, NULL, 0);
pthread_mutex_init(&o->replace_mutex, NULL);
return o;
}
static void free_object_directory(struct object_directory *odb)
{
free(odb->path);
odb_clear_loose_cache(odb);
free(odb);
}
static void free_object_directories(struct raw_object_store *o)
{
while (o->odb) {
struct object_directory *next;
next = o->odb->next;
free_object_directory(o->odb);
o->odb = next;
}
}
void raw_object_store_clear(struct raw_object_store *o)
{
FREE_AND_NULL(o->alternate_db);
oidmap_free(o->replace_map, 1);
FREE_AND_NULL(o->replace_map);
pthread_mutex_destroy(&o->replace_mutex);
free_commit_graph(o->commit_graph);
o->commit_graph = NULL;
o->commit_graph_attempted = 0;
free_object_directories(o);
o->odb_tail = NULL;
o->loaded_alternates = 0;
INIT_LIST_HEAD(&o->packed_git_mru);
close_object_store(o);
o->packed_git = NULL;
hashmap_free(&o->pack_map);
}
void parsed_object_pool_clear(struct parsed_object_pool *o)
{
/*
* As objects are allocated in slabs (see alloc.c), we do
* not need to free each object, but each slab instead.
*
* Before doing so, we need to free any additional memory
* the objects may hold.
*/
unsigned i;
for (i = 0; i < o->obj_hash_size; i++) {
struct object *obj = o->obj_hash[i];
if (!obj)
continue;
if (obj->type == OBJ_TREE)
free_tree_buffer((struct tree*)obj);
else if (obj->type == OBJ_COMMIT)
release_commit_memory(o, (struct commit*)obj);
else if (obj->type == OBJ_TAG)
release_tag_memory((struct tag*)obj);
}
FREE_AND_NULL(o->obj_hash);
o->obj_hash_size = 0;
free_commit_buffer_slab(o->buffer_slab);
o->buffer_slab = NULL;
clear_alloc_state(o->blob_state);
clear_alloc_state(o->tree_state);
clear_alloc_state(o->commit_state);
clear_alloc_state(o->tag_state);
clear_alloc_state(o->object_state);
stat_validity_clear(o->shallow_stat);
FREE_AND_NULL(o->blob_state);
FREE_AND_NULL(o->tree_state);
FREE_AND_NULL(o->commit_state);
FREE_AND_NULL(o->tag_state);
FREE_AND_NULL(o->object_state);
FREE_AND_NULL(o->shallow_stat);
}