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Params: use a multiple-reader / single-writer flock to improve concurrency (#2207)

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* improve concurrency: multiple readers, single writer locks

* remove lock in read_db_value
old-commit-hash: 4fba3408c41fad12a75533cf189686601f9e49a6
This commit is contained in:
Dean Lee
2020-09-24 17:51:36 +08:00
committed by GitHub
parent b48d1823e9
commit f5ec24f42f
2 changed files with 13 additions and 38 deletions
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selfdrive/common/params.cc
+5 -31
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@@ -268,45 +268,19 @@ cleanup:
}
int read_db_value(const char* key, char** value, size_t* value_sz, bool persistent_param) {
int lock_fd = -1;
int result;
char path[1024];
const char* params_path = persistent_param ? persistent_params_path : default_params_path;
result = snprintf(path, sizeof(path), "%s/.lock", params_path);
int result = snprintf(path, sizeof(path), "%s/d/%s", params_path, key);
if (result < 0) {
goto cleanup;
}
lock_fd = open(path, 0);
result = snprintf(path, sizeof(path), "%s/d/%s", params_path, key);
if (result < 0) {
goto cleanup;
return result;
}
// Take lock.
result = flock(lock_fd, LOCK_EX);
if (result < 0) {
goto cleanup;
}
// Read value.
// TODO(mgraczyk): If there is a lot of contention, we can release the lock
// after opening the file, before reading.
*value = static_cast<char*>(read_file(path, value_sz));
if (*value == NULL) {
result = -22;
goto cleanup;
return -22;
}
result = 0;
cleanup:
// Release lock.
if (lock_fd >= 0) {
close(lock_fd);
}
return result;
return 0;
}
void read_db_value_blocking(const char* key, char** value, size_t* value_sz, bool persistent_param) {
@@ -330,7 +304,7 @@ int read_db_all(std::map<std::string, std::string> *params, bool persistent_para
int lock_fd = open(lock_path.c_str(), 0);
if (lock_fd < 0) return -1;
err = flock(lock_fd, LOCK_EX);
err = flock(lock_fd, LOCK_SH);
if (err < 0) return err;
std::string key_path = util::string_format("%s/d", params_path);