Introduce stack snapshotting / cloning (#18741)

Add `StackSnapshot#` primitive type that represents a cloned stack (StgStack).
The cloning interface consists of two functions, that clone either the treads
own stack (cloneMyStack) or another threads stack (cloneThreadStack).

The stack snapshot is offline/cold, i.e. it isn't evaluated any further. This is
useful for analyses as it prevents concurrent modifications.

For technical details, please see Note [Stack Cloning].

Co-authored-by: Ben Gamari <bgamari.foss@gmail.com>
Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/rts/Messages.c b/rts/Messages.c
index 8cd0a5570f..2ec12da3ad 100644
--- a/rts/Messages.c
+++ b/rts/Messages.c
@@ -14,6 +14,7 @@
 #include "Threads.h"
 #include "RaiseAsync.h"
 #include "sm/Storage.h"
+#include "CloneStack.h"
 
 /* ----------------------------------------------------------------------------
    Send a message to another Capability
@@ -32,7 +33,8 @@ void sendMessage(Capability *from_cap, Capability *to_cap, Message *msg)
             i != &stg_MSG_BLACKHOLE_info &&
             i != &stg_MSG_TRY_WAKEUP_info &&
             i != &stg_IND_info && // can happen if a MSG_BLACKHOLE is revoked
-            i != &stg_WHITEHOLE_info) {
+            i != &stg_WHITEHOLE_info &&
+            i != &stg_MSG_CLONE_STACK_info) {
             barf("sendMessage: %p", i);
         }
     }
@@ -130,6 +132,10 @@ loop:
 #endif
         goto loop;
     }
+    else if(i == &stg_MSG_CLONE_STACK_info){
+        MessageCloneStack *cloneStackMessage = (MessageCloneStack*) m;
+        handleCloneStackMessage(cloneStackMessage);
+    }
     else
     {
         barf("executeMessage: %p", i);