fix bug in transfer initiation checking

Putting the transfer on the currentTransfers atomically introduced a bug:
It checks to see if the transfer is in progress, and cancels it.

Fixed by moving that check inside the STM transaction.
This commit is contained in:
Joey Hess 2012-07-29 13:37:26 -04:00
parent 09e77a0cf0
commit ebd8362d58
2 changed files with 37 additions and 32 deletions

View file

@ -113,16 +113,22 @@ queueTransferAt wantsz schedule q dstatus f t remote = do
else retry -- blocks until queuesize changes
enqueue schedule q dstatus t (stubInfo f remote)
{- Blocks until a pending transfer is available from the queue.
- The transfer is removed from the transfer queue, and added to
- the daemon status currentTransfers map. This is done in a single STM
- transaction, so there is no window where an observer sees an
- inconsistent status. -}
getNextTransfer :: TransferQueue -> DaemonStatusHandle -> IO (Transfer, TransferInfo)
getNextTransfer q dstatus = atomically $ do
{- Blocks until a pending transfer is available from the queue,
- and removes it.
-
- Checks that it's acceptable, before adding it to the
- the currentTransfers map. If it's not acceptable, it's discarded.
-
- This is done in a single STM transaction, so there is no window
- where an observer sees an inconsistent status. -}
getNextTransfer :: TransferQueue -> DaemonStatusHandle -> (TransferInfo -> Bool) -> IO (Maybe (Transfer, TransferInfo))
getNextTransfer q dstatus acceptable = atomically $ do
void $ modifyTVar' (queuesize q) pred
void $ modifyTVar' (queuelist q) (drop 1)
r@(t, info) <- readTChan (queue q)
adjustTransfersSTM dstatus $
M.insertWith' const t info
return r
if acceptable info
then do
adjustTransfersSTM dstatus $
M.insertWith' const t info
return $ Just r
else return Nothing