[Git][ghc/ghc][wip/tsan/fixes] 3 commits: Fix acquire fences on indirections

[Ben Gamari (@bgamari)]

Ben Gamari pushed to branch wip/tsan/fixes at Glasgow Haskell Compiler / GHC


Commits:
9d911f17 by Ubuntu at 2023-04-24T09:35:15+00:00
Fix acquire fences on indirections

- - - - -
39446503 by Ubuntu at 2023-04-24T09:36:09+00:00
STM

- - - - -
3caadbd5 by Ubuntu at 2023-04-24T09:36:29+00:00
comment fixes

- - - - -


3 changed files:

- rts/STM.c
- rts/StgMiscClosures.cmm
- rts/include/stg/SMP.h


Changes:

=====================================
rts/STM.c
=====================================
@@ -294,7 +294,7 @@ static StgClosure *lock_tvar(Capability *cap,
     StgInfoTable *info;
     do {
       result = ACQUIRE_LOAD(&s->current_value);
-      info = GET_INFO_RELAXED(UNTAG_CLOSURE(result));
+      info = GET_INFO(UNTAG_CLOSURE(result));
     } while (info == &stg_TREC_HEADER_info);
   } while (cas((void *) &s->current_value,
                (StgWord)result, (StgWord)trec) != (StgWord)result);


=====================================
rts/StgMiscClosures.cmm
=====================================
@@ -521,6 +521,7 @@ INFO_TABLE(stg_IND,1,0,IND,"IND","IND")
     (P_ node)
 {
     TICK_ENT_DYN_IND(); /* tick */
+    ACQUIRE_FENCE_ON(node + OFFSET_StgHeader_info);
     node = %acquire StgInd_indirectee(node);
     node = UNTAG(node);
     TICK_ENT_VIA_NODE();
@@ -530,6 +531,7 @@ INFO_TABLE(stg_IND,1,0,IND,"IND","IND")
     /* explicit stack */
 {
     TICK_ENT_DYN_IND(); /* tick */
+    ACQUIRE_FENCE_ON(R1 + OFFSET_StgHeader_info);
     P_ p;
     p = %acquire StgInd_indirectee(R1);
     R1 = UNTAG(p);
@@ -542,6 +544,7 @@ INFO_TABLE(stg_IND_STATIC,1,0,IND_STATIC,"IND_STATIC","IND_STATIC")
     /* explicit stack */
 {
     TICK_ENT_STATIC_IND(); /* tick */
+    ACQUIRE_FENCE_ON(R1 + OFFSET_StgHeader_info);
     P_ p;
     p = %acquire StgInd_indirectee(R1);
     R1 = UNTAG(p);
@@ -569,7 +572,7 @@ INFO_TABLE(stg_BLACKHOLE,1,0,BLACKHOLE,"BLACKHOLE","BLACKHOLE")
 retry:
     // Synchronizes with the SET_INFO_RELEASE in
     // updateWithIndirection
-    ACQUIRE_FENCE_ON(StgHeader_info(node));
+    ACQUIRE_FENCE_ON(node + OFFSET_StgHeader_info);
 
     // Synchronizes with the release-store in
     // updateWithIndirection.
@@ -678,7 +681,7 @@ loop:
         // defined in CMM.
         goto loop;
     }
-    ACQUIRE_FENCE_ON(StgHeader_info(node));
+    ACQUIRE_FENCE_ON(node + OFFSET_StgHeader_info);
     jump %ENTRY_CODE(info) (node);
 #else
     ccall barf("WHITEHOLE object (%p) entered!", R1) never returns;


=====================================
rts/include/stg/SMP.h
=====================================
@@ -277,7 +277,7 @@ EXTERN_INLINE void load_load_barrier(void);
  *  U1. use a release-store to place the new indirectee into the thunk's
  *      indirectee field
  *
- *  U2. use a relaxed-store to set the info table to stg_BLACKHOLE (which
+ *  U2. use a release-store to set the info table to stg_BLACKHOLE (which
  *      represents an indirection)
  *
  * Blackholing a thunk (either eagerly, by GHC.StgToCmm.Bind.emitBlackHoleCode,
@@ -299,7 +299,7 @@ EXTERN_INLINE void load_load_barrier(void);
  *
  *  E4. enter the indirectee (or block if the indirectee is a TSO)
  *
- * The acquire-fence in step (E2) is somewhat surprising but is necessary as
+ * The release/acquire pair (U2)/(E2) is somewhat surprising but is necessary as
  * the C11 memory model does not guarantee that the store (U1) is visible to
  * (E3) despite (U1) preceding (U2) in program-order (due to the relaxed
  * ordering of (E3)). This is demonstrated by the following CppMem model:



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/e1bd66c4aa70f2a0130820cbac48a017f76eacf9...3caadbd50211ef5fddbcefcba17b4c5baaa1793e

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/e1bd66c4aa70f2a0130820cbac48a017f76eacf9...3caadbd50211ef5fddbcefcba17b4c5baaa1793e
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