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70563867a6
`self.accounts.read().await.get_all()` acquires a read lock and does not release it until the end of `for` loop. After that, a writer may get into the queue, e.g. because of the concurrent `add_account` call. In this case `let context_option = self.accounts.read().await.get_account(id);` tries to acquire another read lock and deadlocks because tokio RwLock is write-preferring and will not give another read lock while there is a writer in the queue. At the same time, writer never gets a write lock because the first read lock is not released. The fix is to get a single read lock for the whole `get_all_accounts()` call. This is described in <https://docs.rs/tokio/1.44.1/tokio/sync/struct.RwLock.html#method.read>: "Note that under the priority policy of RwLock, read locks are not granted until prior write locks, to prevent starvation. Therefore deadlock may occur if a read lock is held by the current task, a write lock attempt is made, and then a subsequent read lock attempt is made by the current task."