Do not link ghc stage1 using -threaded, only for stage2 or 3

[ghc-hetmet.git] / rts / HeapStackCheck.cmm

diff --git a/rts/HeapStackCheck.cmm b/rts/HeapStackCheck.cmm
index 94cec38..a1b6d65 100644 (file)
--- a/rts/HeapStackCheck.cmm
+++ b/rts/HeapStackCheck.cmm
@@ -23,8 +23,22 @@ import LeaveCriticalSection;
  *
  * On discovering that a stack or heap check has failed, we do the following:
  *
- *    - If the context_switch flag is set, indicating that there are more
- *      threads waiting to run, we yield to the scheduler 
+ *    - If HpLim==0, indicating that we should context-switch, we yield
+ *      to the scheduler (return ThreadYielding).
+ *
+ * Note that we must leave no slop in the heap (this is a requirement
+ * for LDV profiling, at least), so if we just had a heap-check
+ * failure, then we must retract Hp by HpAlloc.  How do we know
+ * whether there was a heap-check failure?  HpLim might be zero, and
+ * yet we got here as a result of a stack-check failure.  Hence, we
+ * require that HpAlloc is only non-zero if there was a heap-check
+ * failure, otherwise it is zero, so we can always safely subtract
+ * HpAlloc from Hp.
+ *
+ * Hence, HpAlloc is zeroed in LOAD_THREAD_STATE().
+ *
+ *    - If the context_switch flag is set (the backup plan if setting HpLim
+ *      to 0 didn't trigger a context switch), we yield to the scheduler
  *     (return ThreadYielding).
  *
  *    - If Hp > HpLim, we've had a heap check failure.  This means we've
@@ -61,8 +75,13 @@ import LeaveCriticalSection;
     DEBUG_ONLY(foreign "C" heapCheckFail());                   \
     if (Hp > HpLim) {                                          \
         Hp = Hp - HpAlloc/*in bytes*/;                         \
+        if (HpLim == 0) { \
+                R1 = ThreadYielding;                           \
+                goto sched;                                    \
+        }                                              \
         if (HpAlloc <= BLOCK_SIZE                              \
             && bdescr_link(CurrentNursery) != NULL) {          \
+            HpAlloc = 0;                                        \
             CLOSE_NURSERY();                                   \
             CurrentNursery = bdescr_link(CurrentNursery);      \
             OPEN_NURSERY();                                    \