From: Thomas Schilling <nominolo@googlemail.com>
Date: Fri, 21 Aug 2009 23:53:55 +0000 (+0000)
Subject: Make updates to external package state idempotent.
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=4201e0f80cf3b47093b60c47d7bf733f17912d81;p=ghc-hetmet.git

Make updates to external package state idempotent.

Without this, concurrent updates to the EPS could introduce
overlapping instances (even though they came from the same module).
---

diff --git a/compiler/iface/LoadIface.lhs b/compiler/iface/LoadIface.lhs
index 3a4cfe5..cedc447 100644
--- a/compiler/iface/LoadIface.lhs
+++ b/compiler/iface/LoadIface.lhs
@@ -257,6 +257,7 @@ loadInterface doc_str mod from
                }
 
 	; updateEps_  $ \ eps -> 
+           if elemModuleEnv mod (eps_PIT eps) then eps else
 	    eps { 
 	      eps_PIT          = extendModuleEnv (eps_PIT eps) mod final_iface,
 	      eps_PTE          = addDeclsToPTE   (eps_PTE eps) new_eps_decls,