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Merge branch 'mt/threaded-grep-in-object-store'

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Traditionally, we avoided threaded grep while searching in objects
(as opposed to files in the working tree) as accesses to the object
layer is not thread-safe.  This limitation is getting lifted.

* mt/threaded-grep-in-object-store:
  grep: use no. of cores as the default no. of threads
  grep: move driver pre-load out of critical section
  grep: re-enable threads in non-worktree case
  grep: protect packed_git [re-]initialization
  grep: allow submodule functions to run in parallel
  submodule-config: add skip_if_read option to repo_read_gitmodules()
  grep: replace grep_read_mutex by internal obj read lock
  object-store: allow threaded access to object reading
  replace-object: make replace operations thread-safe
  grep: fix racy calls in grep_objects()
  grep: fix race conditions at grep_submodule()
  grep: fix race conditions on userdiff calls
This commit is contained in:
Junio C Hamano
2020-02-14 12:54:20 -08:00
parent 0da63da794 f1928f04b2
commit 56ceb64eb0
14 changed files with 236 additions and 101 deletions
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99
builtin/grep.c
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@ -24,6 +24,7 @@
#include "submodule.h"
#include "submodule-config.h"
#include "object-store.h"
#include "packfile.h"
static char const * const grep_usage[] = {
N_("git grep [<options>] [-e] <pattern> [<rev>...] [[--] <path>...]"),
@ -32,7 +33,6 @@ static char const * const grep_usage[] = {
static int recurse_submodules;
#define GREP_NUM_THREADS_DEFAULT 8
static int num_threads;
static pthread_t *threads;
@ -91,8 +91,11 @@ static pthread_cond_t cond_result;
static int skip_first_line;
static void add_work(struct grep_opt *opt, const struct grep_source *gs)
static void add_work(struct grep_opt *opt, struct grep_source *gs)
{
if (opt->binary != GREP_BINARY_TEXT)
grep_source_load_driver(gs, opt->repo->index);
grep_lock();
while ((todo_end+1) % ARRAY_SIZE(todo) == todo_done) {
@ -100,9 +103,6 @@ static void add_work(struct grep_opt *opt, const struct grep_source *gs)
}
todo[todo_end].source = *gs;
if (opt->binary != GREP_BINARY_TEXT)
grep_source_load_driver(&todo[todo_end].source,
opt->repo->index);
todo[todo_end].done = 0;
strbuf_reset(&todo[todo_end].out);
todo_end = (todo_end + 1) % ARRAY_SIZE(todo);
@ -200,12 +200,12 @@ static void start_threads(struct grep_opt *opt)
int i;
pthread_mutex_init(&grep_mutex, NULL);
pthread_mutex_init(&grep_read_mutex, NULL);
pthread_mutex_init(&grep_attr_mutex, NULL);
pthread_cond_init(&cond_add, NULL);
pthread_cond_init(&cond_write, NULL);
pthread_cond_init(&cond_result, NULL);
grep_use_locks = 1;
enable_obj_read_lock();
for (i = 0; i < ARRAY_SIZE(todo); i++) {
strbuf_init(&todo[i].out, 0);
@ -257,12 +257,12 @@ static int wait_all(void)
free(threads);
pthread_mutex_destroy(&grep_mutex);
pthread_mutex_destroy(&grep_read_mutex);
pthread_mutex_destroy(&grep_attr_mutex);
pthread_cond_destroy(&cond_add);
pthread_cond_destroy(&cond_write);
pthread_cond_destroy(&cond_result);
grep_use_locks = 0;
disable_obj_read_lock();
return hit;
}
@ -295,16 +295,6 @@ static int grep_cmd_config(const char *var, const char *value, void *cb)
return st;
}
static void *lock_and_read_oid_file(const struct object_id *oid, enum object_type *type, unsigned long *size)
{
void *data;
grep_read_lock();
data = read_object_file(oid, type, size);
grep_read_unlock();
return data;
}
static int grep_oid(struct grep_opt *opt, const struct object_id *oid,
const char *filename, int tree_name_len,
const char *path)
@ -407,30 +397,28 @@ static int grep_submodule(struct grep_opt *opt,
{
struct repository subrepo;
struct repository *superproject = opt->repo;
const struct submodule *sub = submodule_from_path(superproject,
&null_oid, path);
const struct submodule *sub;
struct grep_opt subopt;
int hit;
sub = submodule_from_path(superproject, &null_oid, path);
if (!is_submodule_active(superproject, path))
return 0;
if (repo_submodule_init(&subrepo, superproject, sub))
return 0;
/*
* NEEDSWORK: submodules functions need to be protected because they
* access the object store via config_from_gitmodules(): the latter
* uses get_oid() which, for now, relies on the global the_repository
* object.
* NEEDSWORK: repo_read_gitmodules() might call
* add_to_alternates_memory() via config_from_gitmodules(). This
* operation causes a race condition with concurrent object readings
* performed by the worker threads. That's why we need obj_read_lock()
* here. It should be removed once it's no longer necessary to add the
* subrepo's odbs to the in-memory alternates list.
*/
grep_read_lock();
if (!is_submodule_active(superproject, path)) {
grep_read_unlock();
return 0;
}
if (repo_submodule_init(&subrepo, superproject, sub)) {
grep_read_unlock();
return 0;
}
repo_read_gitmodules(&subrepo);
obj_read_lock();
repo_read_gitmodules(&subrepo, 0);
/*
* NEEDSWORK: This adds the submodule's object directory to the list of
@ -443,7 +431,7 @@ static int grep_submodule(struct grep_opt *opt,
* object.
*/
add_to_alternates_memory(subrepo.objects->odb->path);
grep_read_unlock();
obj_read_unlock();
memcpy(&subopt, opt, sizeof(subopt));
subopt.repo = &subrepo;
@ -455,14 +443,12 @@ static int grep_submodule(struct grep_opt *opt,
unsigned long size;
struct strbuf base = STRBUF_INIT;
obj_read_lock();
object = parse_object_or_die(oid, oid_to_hex(oid));
grep_read_lock();
obj_read_unlock();
data = read_object_with_reference(&subrepo,
&object->oid, tree_type,
&size, NULL);
grep_read_unlock();
if (!data)
die(_("unable to read tree (%s)"), oid_to_hex(&object->oid));
@ -587,7 +573,7 @@ static int grep_tree(struct grep_opt *opt, const struct pathspec *pathspec,
void *data;
unsigned long size;
data = lock_and_read_oid_file(&entry.oid, &type, &size);
data = read_object_file(&entry.oid, &type, &size);
if (!data)
die(_("unable to read tree (%s)"),
oid_to_hex(&entry.oid));
@ -625,12 +611,9 @@ static int grep_object(struct grep_opt *opt, const struct pathspec *pathspec,
struct strbuf base;
int hit, len;
grep_read_lock();
data = read_object_with_reference(opt->repo,
&obj->oid, tree_type,
&size, NULL);
grep_read_unlock();
if (!data)
die(_("unable to read tree (%s)"), oid_to_hex(&obj->oid));
@ -659,13 +642,18 @@ static int grep_objects(struct grep_opt *opt, const struct pathspec *pathspec,
for (i = 0; i < nr; i++) {
struct object *real_obj;
obj_read_lock();
real_obj = deref_tag(opt->repo, list->objects[i].item,
NULL, 0);
obj_read_unlock();
/* load the gitmodules file for this rev */
if (recurse_submodules) {
submodule_free(opt->repo);
obj_read_lock();
gitmodules_config_oid(&real_obj->oid);
obj_read_unlock();
}
if (grep_object(opt, pathspec, real_obj, list->objects[i].name,
list->objects[i].path)) {
@ -1065,7 +1053,10 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
pathspec.recursive = 1;
pathspec.recurse_submodules = !!recurse_submodules;
if (list.nr || cached || show_in_pager) {
if (recurse_submodules && untracked)
die(_("--untracked not supported with --recurse-submodules"));
if (show_in_pager) {
if (num_threads > 1)
warning(_("invalid option combination, ignoring --threads"));
num_threads = 1;
@ -1075,7 +1066,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
} else if (num_threads < 0)
die(_("invalid number of threads specified (%d)"), num_threads);
else if (num_threads == 0)
num_threads = HAVE_THREADS ? GREP_NUM_THREADS_DEFAULT : 1;
num_threads = HAVE_THREADS ? online_cpus() : 1;
if (num_threads > 1) {
if (!HAVE_THREADS)
@ -1084,6 +1075,17 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
&& (opt.pre_context || opt.post_context ||
opt.file_break || opt.funcbody))
skip_first_line = 1;
/*
* Pre-read gitmodules (if not read already) and force eager
* initialization of packed_git to prevent racy lazy
* reading/initialization once worker threads are started.
*/
if (recurse_submodules)
repo_read_gitmodules(the_repository, 1);
if (startup_info->have_repository)
(void)get_packed_git(the_repository);
start_threads(&opt);
} else {
/*
@ -1118,9 +1120,6 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
}
}
if (recurse_submodules && untracked)
die(_("--untracked not supported with --recurse-submodules"));
if (!show_in_pager && !opt.status_only)
setup_pager();