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This has since been applied to net, so for the record: [Medium] Drop lost when the transport refuses it: right, a drop that hits a full UL ring (or a failed allocation) and is followed by a raise within the 10ms retry still reaches the modem as just the raise. The commit message calls this out, but the new comment overstates it. Tracking an unsent drop until it is queued is roughly what v1 did, and Loic found that too heavy for this case, so the flush stays best effort. On the flush in stop(), a retry left armed after a failed attempt can fire after mhi_unprepare_from_transfer(). That isn't new, v10 had no flush in stop() at all, so the work could already run after the channel stopped. The message goes out on the IP_CTRL channel, which is still running, the AT channel only appears as dest_id. If the port is reopened before the retry fires, the retry sends the latest state, i.e. the raise from the reopen, so the modem ends up in the right state. [Low] Stale comments: agreed. I'll send a comment-only patch for net-next that says the drop flush is best effort, mentions it in the dtr_mdmbits comment and drops "one attempt" from the remove() comment.