From 8901285ef64ab4aa16aa34096a1e2be42d4be246 Mon Sep 17 00:00:00 2001
From: Duncan Coutts <duncan@well-typed.com>
Date: Tue, 29 Dec 2020 00:51:32 +0000
Subject: Add hook markCapabilityIOManager

To allow I/O managers to have GC roots in the Capability, within the
CapIOManager structure.

Not yet used in this patch.
---
 rts/Capability.c | 2 ++
 rts/IOManager.c  | 7 +++++++
 rts/IOManager.h  | 8 ++++++++
 3 files changed, 17 insertions(+)

diff --git a/rts/Capability.c b/rts/Capability.c
index 05332514e3..afe21fcb46 100644
--- a/rts/Capability.c
+++ b/rts/Capability.c
@@ -1322,6 +1322,8 @@ markCapability (evac_fn evac, void *user, Capability *cap,
     }
 #endif
 
+    markCapabilityIOManager(evac, user, cap->iomgr);
+
     // Free STM structures for this Capability
     stmPreGCHook(cap);
 }
diff --git a/rts/IOManager.c b/rts/IOManager.c
index 6782c3984d..5a6347c537 100644
--- a/rts/IOManager.c
+++ b/rts/IOManager.c
@@ -150,6 +150,13 @@ void wakeupIOManager(void)
 }
 
 
+void markCapabilityIOManager(evac_fn evac STG_UNUSED,
+                             void *user STG_UNUSED,
+                             CapIOManager *iomgr STG_UNUSED)
+{
+}
+
+
 /* Declared in rts/IOInterface.h. Used only by the MIO threaded I/O manager on
  * Unix platforms.
  */
diff --git a/rts/IOManager.h b/rts/IOManager.h
index ed7b4dcdcf..ceb38508ea 100644
--- a/rts/IOManager.h
+++ b/rts/IOManager.h
@@ -21,6 +21,9 @@
 
 #include "BeginPrivate.h"
 
+#include "sm/GC.h" // for evac_fn
+
+
 /* The per-capability data structures belonging to the I/O manager.
  *
  * It can be accessed as cap->iomgr.
@@ -97,6 +100,11 @@ void exitIOManager(bool wait_threads);
 void wakeupIOManager(void);
 
 
+/* GC hook: mark any per-capability GC roots the I/O manager uses.
+ */
+void markCapabilityIOManager(evac_fn evac, void *user, CapIOManager *iomgr);
+
+
 /* Pedantic warning cleanliness
  */
 #if !defined(THREADED_RTS) && defined(mingw32_HOST_OS)
-- 
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