Previous commit uses wrong clock id and forget to release an additional
rdlock. cc @Eric977
Sorry for missing this in my initial review.
Fixes https://github.com/llvm/llvm-project/issues/100960.
Notice that the timestamp is created via
```c++
LIBC_NAMESPACE::clock_gettime(CLOCK_REALTIME, &ts);
ts.tv_nsec += 50'000;
if (ts.tv_nsec >= 1'000'000'000) {
ts.tv_nsec -= 1'000'000'000;
ts.tv_sec += 1;
}
```
5cddc314c8