From ecbd45631261495e7f44cb23f98c18c79553ebb7 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Mon, 17 Jun 2019 12:51:44 -0400
Subject: [PATCH] fix restoring worker pool bug

The bug might have led to a STM deadlock, if this case could ever
actually fire.
---
 CmdLine/Action.hs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/CmdLine/Action.hs b/CmdLine/Action.hs
index 625e8c1cd6..be18af8f90 100644
--- a/CmdLine/Action.hs
+++ b/CmdLine/Action.hs
@@ -193,11 +193,12 @@ changeStageTo newstage = do
 	liftIO $ atomically $ waitWorkerSlot' (== newstage) tv >>= \case
 		Just idlest -> do
 			pool <- takeTMVar tv
+			let restorepool = addWorkerPool (IdleWorker idlest newstage) pool
 			let pool' = case removeThreadIdWorkerPool mytid pool of
 				Just ((myaid, oldstage), p) ->
 					addWorkerPool (IdleWorker idlest oldstage) $
 						addWorkerPool (ActiveWorker myaid newstage) p
-				Nothing -> pool
+				Nothing -> restorepool
 			putTMVar tv pool'
 		-- No worker pool is allocated, not running in concurrent
 		-- mode.