From: Simon Marlow <marlowsd@gmail.com>
Date: Fri, 3 Dec 2010 09:48:18 +0000 (+0000)
Subject: handle ThreadMigrating in throwTo() (#4811)
X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=e9c6b0de1890a66a9ce2e7749eaf7d7317c9dd01

handle ThreadMigrating in throwTo() (#4811)
If a throwTo targets a thread that has just been created with
forkOnIO, then it is possible the exception strikes while the thread
is still in the process of migrating.  throwTo() didn't handle this
case, but it's fairly straightforward.
---

diff --git a/rts/RaiseAsync.c b/rts/RaiseAsync.c
index 628dff8..3cfb450 100644
--- a/rts/RaiseAsync.c
+++ b/rts/RaiseAsync.c
@@ -436,6 +436,18 @@ check_target:
 	}
 #endif
 
+    case ThreadMigrating:
+        // if is is ThreadMigrating and tso->cap is ours, then it
+        // *must* be migrating *to* this capability.  If it were
+        // migrating away from the capability, then tso->cap would
+        // point to the destination.
+        //
+        // There is a MSG_WAKEUP in the message queue for this thread,
+        // but we can just do it preemptively:
+        tryWakeupThread(cap, target);
+        // and now retry, the thread should be runnable.
+        goto retry;
+
     default:
 	barf("throwTo: unrecognised why_blocked value");
     }