The login cache is shared by every mdrs process, but the refresh was
guarded by a lock that only reaches inside one. Concurrent runs each
sent the same refresh token, and a provider that rotates them accepts
the first and refuses the rest.
- hold a lock that spans processes across the whole read-refresh-
write, checking cheaply first so ordinary requests never take it
- write the cache through a temporary file: opening it for writing
truncates it, and a reader landing in that window found it empty
and threw the session away
- take the lock for every write, not just the refresh, so a login
running beside one cannot be silently reverted
- wait for a busy lock on Windows rather than giving up after the ten
attempts msvcrt allows, and retry the rename it refuses while a
reader still holds the file open
- bound the refresh request on its own, so a provider that goes quiet
cannot hold the lock indefinitely
- accept bare hostnames such as localhost, store URLs without the
trailing slash, and join download paths through one helper
orrisroot
pw-serizawa