X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=rts%2FCapability.h;h=3f01bf3d8898af3f86993b486e7479f73a0a3966;hp=b6f6440cb8692ccccba63e56c72e56bcd7397075;hb=6cf8982ac30be6836a0cdd8be5a6ac1a1a144213;hpb=022ee7c728822c4dd5be226f75e44557b4a3d9a1

diff --git a/rts/Capability.h b/rts/Capability.h
index b6f6440..3f01bf3 100644
--- a/rts/Capability.h
+++ b/rts/Capability.h
@@ -4,29 +4,26 @@
  *
  * Capabilities
  *
- * The notion of a capability is used when operating in multi-threaded
- * environments (which the THREADED_RTS build of the RTS does), to
- * hold all the state an OS thread/task needs to run Haskell code:
- * its STG registers, a pointer to its  TSO, a nursery etc. During
- * STG execution, a pointer to the capabilitity is kept in a 
- * register (BaseReg).
+ * A Capability holds all the state an OS thread/task needs to run
+ * Haskell code: its STG registers, a pointer to its TSO, a nursery
+ * etc. During STG execution, a pointer to the Capabilitity is kept in
+ * a register (BaseReg).
  *
- * Only in an THREADED_RTS build will there be multiple capabilities,
- * in the non-threaded builds there is one global capability, namely
+ * Only in a THREADED_RTS build will there be multiple capabilities,
+ * in the non-threaded RTS there is one global capability, called
  * MainCapability.
  *
- * This header file contains the functions for working with capabilities.
- * (the main, and only, consumer of this interface is the scheduler).
- * 
  * --------------------------------------------------------------------------*/
 
 #ifndef CAPABILITY_H
 #define CAPABILITY_H
 
-#include "RtsFlags.h"
+#include "sm/GC.h" // for evac_fn
 #include "Task.h"
 #include "Sparks.h"
 
+BEGIN_RTS_PRIVATE
+
 struct Capability_ {
     // State required by the STG virtual machine when running Haskell
     // code.  During STG execution, the BaseReg register always points
@@ -65,10 +62,12 @@ struct Capability_ {
     Task *suspended_ccalling_tasks;
 
     // One mutable list per generation, so we don't need to take any
-    // locks when updating an old-generation thunk.  These
-    // mini-mut-lists are moved onto the respective gen->mut_list at
-    // each GC.
+    // locks when updating an old-generation thunk.  This also lets us
+    // keep track of which closures this CPU has been mutating, so we
+    // can traverse them using the right thread during GC and avoid
+    // unnecessarily moving the data from one cache to another.
     bdescr **mut_lists;
+    bdescr **saved_mut_lists; // tmp use during GC
 
     // Context switch flag. We used to have one global flag, now one 
     // per capability. Locks required  : none (conflicts are harmless)
@@ -143,12 +142,10 @@ struct Capability_ {
 
 // Converts a *StgRegTable into a *Capability.
 //
-#define OFFSET(s_type, field) ((size_t)&(((s_type*)0)->field))
-
 INLINE_HEADER Capability *
 regTableToCapability (StgRegTable *reg)
 {
-    return (Capability *)((void *)((unsigned char*)reg - OFFSET(Capability,r)));
+    return (Capability *)((void *)((unsigned char*)reg - STG_FIELD_OFFSET(Capability,r)));
 }
 
 // Initialise the available capabilities.
@@ -174,14 +171,14 @@ INLINE_HEADER void releaseCapability_ (Capability* cap STG_UNUSED,
                                        rtsBool always_wakeup STG_UNUSED) {};
 #endif
 
-#if !IN_STG_CODE
-// one global capability
-extern Capability MainCapability; 
-#endif
+// declared in includes/rts/Threads.h:
+// extern Capability MainCapability; 
+
+// declared in includes/rts/Threads.h:
+// extern nat n_capabilities;
 
 // Array of all the capabilities
 //
-extern nat n_capabilities;
 extern Capability *capabilities;
 
 // The Capability that was last free.  Used as a good guess for where
@@ -276,11 +273,12 @@ extern void grabCapability (Capability **pCap);
 
 // cause all capabilities to context switch as soon as possible.
 void setContextSwitches(void);
+INLINE_HEADER void contextSwitchCapability(Capability *cap);
 
 // Free all capabilities
 void freeCapabilities (void);
 
-// FOr the GC:
+// For the GC:
 void markSomeCapabilities (evac_fn evac, void *user, nat i0, nat delta, 
                            rtsBool prune_sparks);
 void markCapabilities (evac_fn evac, void *user);
@@ -322,4 +320,18 @@ discardSparksCap (Capability *cap)
 { return discardSparks(cap->sparks); }
 #endif
 
+INLINE_HEADER void
+contextSwitchCapability (Capability *cap)
+{
+    // setting HpLim to NULL ensures that the next heap check will
+    // fail, and the thread will return to the scheduler.
+    cap->r.rHpLim = NULL;
+    // But just in case it didn't work (the target thread might be
+    // modifying HpLim at the same time), we set the end-of-block
+    // context-switch flag too:
+    cap->context_switch = 1;
+}
+
+END_RTS_PRIVATE
+
 #endif /* CAPABILITY_H */