go: add deadlock detector, improve locking #618
Conversation
This file contains 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
Signed-off-by: David Scott <[email protected]>
Signed-off-by: David Scott <[email protected]>
Signed-off-by: David Scott <[email protected]>
The code is clearer if each object only acquires its own mutex, and doesn't reach into the mutexes of others (if possible) Signed-off-by: David Scott <[email protected]>
The Write window is used to keep track of how much buffer space is free in the remote to avoid one connection blocking the rest. Previously we checked the window and decided how much to write, then dropped the metadata mutex before performing the write. In theory another Write call on the same connection could see that buffer size is free, send too much and block the connection. Therefore Write should take ownership of the space by bumping the `current` window before dropping the lock. Signed-off-by: David Scott <[email protected]>
Previously we had a complicated set of channels and a condition variable, and the condition variable Wait() was in a goroutine. Instead the Wait() is now in the main goroutine and an optional timeout is in an optional goroutine. Signed-off-by: David Scott <[email protected]>
If multiple calls are blocked waiting for window space, we need to use Broadcast() to wake them all up on a window update. Signed-off-by: David Scott <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
We weren't fully compliant with the
net.Conninterface as concurrentWritecalls had problems:Writecalls could exceed the allowed window size: one would see space available, drop the lock to write, allow a second to see the same space and writeWritecalls could block: when the window is closed they would block inWait()but the window update message only usedSignal()and would only wake up one call, leaving the other blocked. It should useBroadcast().The
Write()timeout handling was strange because it offloaded theWait()to a goroutine. It's simpler to keep theWait()on the main goroutine and do aBroadcast()from anAfterFunc. It's also good to stop the timer in the common case where you don't need it, rather than leave them to build up.Also