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https://git.proxmox.com/git/libgit2
synced 2025-05-28 00:25:29 +00:00
Add git__compare_and_swap and use it
This removes the lock from the repository object and changes the internals to use the new atomic git__compare_and_swap to update the _odb, _config, _index, and _refdb variables in a threadsafe manner.
This commit is contained in:
Russell Belfer
Vicent Marti
parent
5360786885
commit
e976b56dda
@ -10,14 +10,6 @@
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#include "mwindow.h"
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#include "hash.h"
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#if defined(GIT_THREADS) && defined(_MSC_VER)
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# define GIT_MEMORY_BARRIER MemoryBarrier()
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#elif defined(GIT_THREADS)
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# define GIT_MEMORY_BARRIER __sync_synchronize()
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#else
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# define GIT_MEMORY_BARRIER /* noop */
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#endif
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typedef struct {
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git_error *last_error;
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git_error error_t;
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132
src/repository.c
132
src/repository.c
@ -32,43 +32,57 @@
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#define GIT_TEMPLATE_DIR "/usr/share/git-core/templates"
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#define repo_swap_ptr(repo,item_ptr,new_value) \
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git__swap(&repo->lock, (void **)item_ptr, new_value)
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static void drop_odb(git_repository *repo)
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static void set_odb(git_repository *repo, git_odb *odb)
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{
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git_odb *dropme = repo_swap_ptr(repo, &repo->_odb, NULL);
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if (dropme != NULL) {
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GIT_REFCOUNT_OWN(dropme, NULL);
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git_odb_free(dropme);
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if (odb) {
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GIT_REFCOUNT_OWN(odb, repo);
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GIT_REFCOUNT_INC(odb);
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}
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if ((odb = git__swap(repo->_odb, odb)) != NULL) {
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GIT_REFCOUNT_OWN(odb, NULL);
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git_odb_free(odb);
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}
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}
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static void drop_refdb(git_repository *repo)
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static void set_refdb(git_repository *repo, git_refdb *refdb)
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{
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git_refdb *dropme = repo_swap_ptr(repo, &repo->_refdb, NULL);
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if (dropme != NULL) {
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GIT_REFCOUNT_OWN(dropme, NULL);
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git_refdb_free(dropme);
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if (refdb) {
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GIT_REFCOUNT_OWN(refdb, repo);
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GIT_REFCOUNT_INC(refdb);
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}
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if ((refdb = git__swap(repo->_refdb, refdb)) != NULL) {
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GIT_REFCOUNT_OWN(refdb, NULL);
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git_refdb_free(refdb);
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}
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}
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static void drop_config(git_repository *repo)
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static void set_config(git_repository *repo, git_config *config)
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{
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git_config *dropme = repo_swap_ptr(repo, &repo->_config, NULL);
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if (dropme != NULL) {
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GIT_REFCOUNT_OWN(dropme, NULL);
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git_config_free(dropme);
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git_repository__cvar_cache_clear(repo);
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if (config) {
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GIT_REFCOUNT_OWN(config, repo);
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GIT_REFCOUNT_INC(config);
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}
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if ((config = git__swap(repo->_config, config)) != NULL) {
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GIT_REFCOUNT_OWN(config, NULL);
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git_config_free(config);
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}
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git_repository__cvar_cache_clear(repo);
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}
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static void drop_index(git_repository *repo)
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static void set_index(git_repository *repo, git_index *index)
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{
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git_index *dropme = repo_swap_ptr(repo, &repo->_index, NULL);
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if (dropme != NULL) {
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GIT_REFCOUNT_OWN(dropme, NULL);
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git_index_free(dropme);
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if (index) {
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GIT_REFCOUNT_OWN(index, repo);
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GIT_REFCOUNT_INC(index);
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}
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if ((index = git__swap(repo->_index, index)) != NULL) {
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GIT_REFCOUNT_OWN(index, NULL);
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git_index_free(index);
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}
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}
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@ -81,15 +95,14 @@ void git_repository_free(git_repository *repo)
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git_attr_cache_flush(repo);
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git_submodule_config_free(repo);
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drop_config(repo);
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drop_index(repo);
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drop_odb(repo);
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drop_refdb(repo);
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set_config(repo, NULL);
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set_index(repo, NULL);
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set_odb(repo, NULL);
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set_refdb(repo, NULL);
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git__free(repo->path_repository);
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git__free(repo->workdir);
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git_mutex_free(&repo->lock);
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git__free(repo);
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}
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@ -122,8 +135,6 @@ static git_repository *repository_alloc(void)
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memset(repo, 0x0, sizeof(git_repository));
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git_mutex_init(&repo->lock);
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if (git_cache_init(&repo->objects) < 0) {
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git__free(repo);
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return NULL;
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@ -581,7 +592,7 @@ int git_repository_config__weakptr(git_config **out, git_repository *repo)
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if (!error) {
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GIT_REFCOUNT_OWN(config, repo);
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config = repo_swap_ptr(repo, &repo->_config, config);
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config = git__compare_and_swap(&repo->_config, NULL, config);
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if (config != NULL) {
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GIT_REFCOUNT_OWN(config, NULL);
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git_config_free(config);
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@ -609,17 +620,7 @@ int git_repository_config(git_config **out, git_repository *repo)
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void git_repository_set_config(git_repository *repo, git_config *config)
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{
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assert(repo && config);
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GIT_REFCOUNT_OWN(config, repo);
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GIT_REFCOUNT_INC(config);
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config = repo_swap_ptr(repo, &repo->_config, config);
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if (config != NULL) {
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GIT_REFCOUNT_OWN(config, NULL);
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git_config_free(config);
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}
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git_repository__cvar_cache_clear(repo);
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set_config(repo, config);
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}
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int git_repository_odb__weakptr(git_odb **out, git_repository *repo)
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@ -638,7 +639,7 @@ int git_repository_odb__weakptr(git_odb **out, git_repository *repo)
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if (!error) {
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GIT_REFCOUNT_OWN(odb, repo);
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odb = repo_swap_ptr(repo, &repo->_odb, odb);
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odb = git__compare_and_swap(&repo->_odb, NULL, odb);
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if (odb != NULL) {
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GIT_REFCOUNT_OWN(odb, NULL);
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git_odb_free(odb);
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@ -664,15 +665,7 @@ int git_repository_odb(git_odb **out, git_repository *repo)
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void git_repository_set_odb(git_repository *repo, git_odb *odb)
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{
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assert(repo && odb);
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GIT_REFCOUNT_OWN(odb, repo);
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GIT_REFCOUNT_INC(odb);
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odb = repo_swap_ptr(repo, &repo->_odb, odb);
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if (odb != NULL) {
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GIT_REFCOUNT_OWN(odb, NULL);
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git_odb_free(odb);
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}
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set_odb(repo, odb);
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}
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int git_repository_refdb__weakptr(git_refdb **out, git_repository *repo)
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@ -688,7 +681,7 @@ int git_repository_refdb__weakptr(git_refdb **out, git_repository *repo)
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if (!error) {
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GIT_REFCOUNT_OWN(refdb, repo);
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refdb = repo_swap_ptr(repo, &repo->_refdb, refdb);
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refdb = git__compare_and_swap(&repo->_refdb, NULL, refdb);
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if (refdb != NULL) {
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GIT_REFCOUNT_OWN(refdb, NULL);
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git_refdb_free(refdb);
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@ -712,15 +705,7 @@ int git_repository_refdb(git_refdb **out, git_repository *repo)
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void git_repository_set_refdb(git_repository *repo, git_refdb *refdb)
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{
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assert(repo && refdb);
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GIT_REFCOUNT_OWN(refdb, repo);
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GIT_REFCOUNT_INC(refdb);
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refdb = repo_swap_ptr(repo, &repo->_refdb, refdb);
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if (refdb != NULL) {
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GIT_REFCOUNT_OWN(refdb, NULL);
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git_refdb_free(refdb);
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}
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set_refdb(repo, refdb);
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}
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int git_repository_index__weakptr(git_index **out, git_repository *repo)
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@ -739,7 +724,7 @@ int git_repository_index__weakptr(git_index **out, git_repository *repo)
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if (!error) {
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GIT_REFCOUNT_OWN(index, repo);
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index = repo_swap_ptr(repo, &repo->_index, index);
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index = git__compare_and_swap(&repo->_index, NULL, index);
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if (index != NULL) {
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GIT_REFCOUNT_OWN(index, NULL);
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git_index_free(index);
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@ -767,15 +752,7 @@ int git_repository_index(git_index **out, git_repository *repo)
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void git_repository_set_index(git_repository *repo, git_index *index)
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{
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assert(repo && index);
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GIT_REFCOUNT_OWN(index, repo);
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GIT_REFCOUNT_INC(index);
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index = repo_swap_ptr(repo, &repo->_index, index);
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if (index != NULL) {
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GIT_REFCOUNT_OWN(index, NULL);
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git_index_free(index);
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}
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set_index(repo, index);
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}
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static int check_repositoryformatversion(git_config *config)
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@ -1465,14 +1442,13 @@ static int at_least_one_cb(const char *refname, void *payload)
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static int repo_contains_no_reference(git_repository *repo)
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{
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int error;
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error = git_reference_foreach(repo, GIT_REF_LISTALL, at_least_one_cb, NULL);
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int error = git_reference_foreach(repo, GIT_REF_LISTALL, at_least_one_cb, NULL);
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if (error == GIT_EUSER)
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return 0;
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return error == 0 ? 1 : error;
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if (!error)
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return 1;
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return error;
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}
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int git_repository_is_empty(git_repository *repo)
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@ -83,7 +83,6 @@ struct git_repository {
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git_refdb *_refdb;
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git_config *_config;
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git_index *_index;
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git_mutex lock;
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git_cache objects;
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git_attr_cache attrcache;
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@ -68,6 +68,21 @@ GIT_INLINE(int) git_atomic_dec(git_atomic *a)
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#endif
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}
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GIT_INLINE(void *) git___compare_and_swap(
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volatile void **ptr, void *oldval, void *newval)
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{
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bool swapped;
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#if defined(GIT_WIN32)
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swapped = ((LONGLONG)oldval == InterlockedCompareExchange64(
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(LONGLONG volatile *)ptr, (LONGLONG)newval, (LONGLONG)oldval));
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#elif defined(__GNUC__)
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swapped = (__sync_val_compare_and_swap(ptr, oldval, newval) == oldval);
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#else
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# error "Unsupported architecture for atomic operations"
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#endif
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return swapped ? oldval : newval;
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}
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#else
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#define git_thread unsigned int
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@ -101,8 +116,34 @@ GIT_INLINE(int) git_atomic_dec(git_atomic *a)
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return --a->val;
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}
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GIT_INLINE(void *) git___compare_and_swap(
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volatile void **ptr, void *oldval, void *newval)
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{
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if (*ptr == oldval)
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*ptr = newval;
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else
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oldval = newval;
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return oldval;
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}
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#endif
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/* Atomically replace oldval with newval
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* @return oldval if it was replaced or newval if it was not
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*/
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#define git__compare_and_swap(P,O,N) \
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git___compare_and_swap((volatile void **)P, O, N)
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#define git__swap(ptr, val) git__compare_and_swap(&ptr, ptr, val)
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extern int git_online_cpus(void);
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#if defined(GIT_THREADS) && defined(GIT_WIN32)
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# define GIT_MEMORY_BARRIER MemoryBarrier()
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#elif defined(GIT_THREADS)
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# define GIT_MEMORY_BARRIER __sync_synchronize()
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#else
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# define GIT_MEMORY_BARRIER /* noop */
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#endif
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#endif /* INCLUDE_thread_utils_h__ */
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19
src/util.h
19
src/util.h
@ -313,23 +313,4 @@ int git__date_parse(git_time_t *out, const char *date);
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*/
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extern size_t git__unescape(char *str);
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/*
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* Swap a pointer with thread safety, returning old value.
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*/
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GIT_INLINE(void *) git__swap(git_mutex *lock, void **ptr_ptr, void *new_ptr)
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{
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void *old_ptr;
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if (*ptr_ptr == new_ptr)
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return NULL;
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if (git_mutex_lock(lock) < 0)
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return new_ptr;
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old_ptr = *ptr_ptr;
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*ptr_ptr = new_ptr;
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git_mutex_unlock(lock);
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return old_ptr;
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}
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#endif /* INCLUDE_util_h__ */
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