go: add deadlock detector, improve locking #618
+16,813
−751
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Signed-off-by: David Scott <dave@recoil.org>
Signed-off-by: David Scott <dave@recoil.org>
Signed-off-by: David Scott <dave@recoil.org>
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 <dave@recoil.org>
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 <dave@recoil.org>
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 <dave@recoil.org>
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 <dave@recoil.org>
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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