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config: make refresh atomic

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Current code sets the active map to a new one and builds it whilst it's
active. This is a race condition with someone else trying to access the
same config.

Instead, let's build up our new map and swap the active and new one.
This commit is contained in:
Carlos Martín Nieto 2014-03-18 17:54:32 +01:00
parent 29c4cb0965
commit c047317e40
1 changed files with 16 additions and 23 deletions
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39
src/config_file.c
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@ -107,7 +107,7 @@ typedef struct {
diskfile_backend *snapshot_from;
} diskfile_readonly_backend;
static int config_parse(diskfile_backend *cfg_file, struct reader *reader, git_config_level_t level, int depth);
static int config_parse(git_strmap *values, diskfile_backend *cfg_file, struct reader *reader, git_config_level_t level, int depth);
static int parse_variable(struct reader *reader, char **var_name, char **var_value);
static int config_write(diskfile_backend *cfg, const char *key, const regex_t *preg, const char *value);
static char *escape_value(const char *ptr);
@ -243,7 +243,7 @@ static int config_open(git_config_backend *cfg, git_config_level_t level)
if (res == GIT_ENOTFOUND)
return 0;
if (res < 0 || (res = config_parse(b, reader, level, 0)) < 0) {
if (res < 0 || (res = config_parse(b->header.values, b, reader, level, 0)) < 0) {
free_vars(b->header.values);
b->header.values = NULL;
}
@ -256,47 +256,41 @@ static int config_open(git_config_backend *cfg, git_config_level_t level)
static int config_refresh(git_config_backend *cfg)
{
int res = 0, updated = 0, any_updated = 0;
int error = 0, updated = 0, any_updated = 0;
diskfile_backend *b = (diskfile_backend *)cfg;
git_strmap *old_values;
git_strmap *values = NULL;
struct reader *reader = NULL;
uint32_t i;
for (i = 0; i < git_array_size(b->readers); i++) {
reader = git_array_get(b->readers, i);
res = git_futils_readbuffer_updated(
error = git_futils_readbuffer_updated(
&reader->buffer, reader->file_path,
&reader->file_mtime, &reader->file_size, &updated);
if (res < 0)
return (res == GIT_ENOTFOUND) ? 0 : res;
if (error < 0)
return (error == GIT_ENOTFOUND) ? 0 : error;
if (updated)
any_updated = 1;
}
if (!any_updated)
return (res == GIT_ENOTFOUND) ? 0 : res;
return (error == GIT_ENOTFOUND) ? 0 : error;
/* need to reload - store old values and prep for reload */
old_values = b->header.values;
if ((res = git_strmap_alloc(&b->header.values)) < 0) {
b->header.values = old_values;
if ((error = git_strmap_alloc(&values)) < 0)
goto cleanup;
}
if ((res = config_parse(b, reader, b->level, 0)) < 0) {
free_vars(b->header.values);
b->header.values = old_values;
if ((error = config_parse(values, b, reader, b->level, 0)) < 0)
goto cleanup;
}
free_vars(old_values);
values = git__swap(b->header.values, values);
cleanup:
free_vars(values);
git_buf_free(&reader->buffer);
return res;
return error;
}
static void backend_free(git_config_backend *_backend)
@ -1218,7 +1212,7 @@ static int included_path(git_buf *out, const char *dir, const char *path)
return git_path_join_unrooted(out, path, dir, NULL);
}
static int config_parse(diskfile_backend *cfg_file, struct reader *reader, git_config_level_t level, int depth)
static int config_parse(git_strmap *values, diskfile_backend *cfg_file, struct reader *reader, git_config_level_t level, int depth)
{
int c;
char *current_section = NULL;
@ -1228,7 +1222,6 @@ static int config_parse(diskfile_backend *cfg_file, struct reader *reader, git_c
git_buf buf = GIT_BUF_INIT;
int result = 0;
uint32_t reader_idx;
git_strmap *values = cfg_file->header.values;
if (depth >= MAX_INCLUDE_DEPTH) {
giterr_set(GITERR_CONFIG, "Maximum config include depth reached");
@ -1327,7 +1320,7 @@ static int config_parse(diskfile_backend *cfg_file, struct reader *reader, git_c
&r->file_size, NULL)) < 0)
break;
result = config_parse(cfg_file, r, level, depth+1);
result = config_parse(values, cfg_file, r, level, depth+1);
r = git_array_get(cfg_file->readers, index);
git_buf_free(&r->buffer);