mirror of https://github.com/zulip/zulip.git
003fa7adda
Fundamentally, we should take a write lock on the message, check its validity for a change, and then make and commit that change. Previously, `check_update_message` did not operate in a transaction, but `do_update_message` did -- which led to the ordering: - `check_update_message` reads Message, not in a transaction - `check_update_message` verifies properties of the Message - `do_update_message` starts a transaction - `do_update_message` takes a read lock on UserMessage - `do_update_message` writes on UserMessage - `do_update_message` writes Message - `do_update_message` commits This leads to race conditions, where the `check_update_message` may have verified based on stale data, and `do_update_message` may improperly overwrite it; as well as deadlocks, where other (properly-written) codepaths take a write lock on Message _before_ updating UserMessage, and thus deadlock with `do_update_message`. Change `check_update_message` to open a transaction, and take the write lock when first accessing the Message row. We update the comment above `do_update_message` to clarify this expectation. The new ordering is thus: - `check_update_message` starts a transaction - `check_update_message` takes a write lock on Message - `check_update_message` verifies properties of the Message - `do_update_message` writes on UserMessage - `do_update_message` writes Message - `check_update_message` commits |
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| .. | ||
| __init__.py | ||
| alert_words.py | ||
| bots.py | ||
| create_realm.py | ||
| create_user.py | ||
| custom_profile_fields.py | ||
| default_streams.py | ||
| hotspots.py | ||
| invites.py | ||
| message_delete.py | ||
| message_edit.py | ||
| message_flags.py | ||
| message_send.py | ||
| muted_users.py | ||
| presence.py | ||
| reactions.py | ||
| realm_domains.py | ||
| realm_emoji.py | ||
| realm_export.py | ||
| realm_icon.py | ||
| realm_linkifiers.py | ||
| realm_logo.py | ||
| realm_playgrounds.py | ||
| realm_settings.py | ||
| scheduled_messages.py | ||
| streams.py | ||
| submessage.py | ||
| typing.py | ||
| uploads.py | ||
| user_activity.py | ||
| user_groups.py | ||
| user_settings.py | ||
| user_status.py | ||
| user_topics.py | ||
| users.py | ||
| video_calls.py | ||