ubusd: avoid client_cb stalls after short reads#23
Open
richard-chyu wants to merge 1 commit into
Open
Conversation
client_cb() uses edge-triggered uloop events for client sockets. If a recvmsg() or read() returns fewer bytes than requested, there may still be data buffered on the socket, but no further read event is guaranteed. After making progress on an incomplete header or message body, retry the receive path immediately instead of returning to the event loop. Also treat a zero-length recvmsg() as no progress/EOF, avoiding a retry loop on a closed connection. Signed-off-by: Richard Yu <richard.yu@mitrastar.com.tw>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This fixes a rare receive stall in
ubusdclient_cb().client sockets are registered with
ULOOP_EDGE_TRIGGER. A short positiverecvmsg()/read()can leave unread data in the socket buffer, but the current code returns to the event loop and assumes another readable event will arrive. With edge-triggered polling, that is not guaranteed if no additional data arrives to create another readiness edge.Retry the receive path immediately after making progress on an incomplete header/body read. Also treat
recvmsg() == 0as no progress/EOF to avoid retrying on a closed connection.