Commit a9dc9658 authored by Simon Marlow's avatar Simon Marlow
Browse files

Fix a really nasty bug in SMP

In SMP mode a THUNK can change to an IND at any time.  The generic
apply code (stg_ap_p etc.) examines a closure to determine how to
apply it to its arguments, if it is a THUNK it must enter it first in
order to evaluate it.  The problem was that in order to enter the
THUNK, we were re-reading the info pointer, and possibly ending up
with an IND instead of the original THUNK.  It isn't safe to enter the
IND, because it points to a function (functions are never "entered",
only applied).  Solution: we must not re-read the info pointer.
parent 2f861d14
......@@ -464,8 +464,10 @@ exprOp name args_code =
exprMacros :: UniqFM ([CmmExpr] -> CmmExpr)
exprMacros = listToUFM [
( FSLIT("ENTRY_CODE"), \ [x] -> entryCode x ),
( FSLIT("GET_ENTRY"), \ [x] -> entryCode (closureInfoPtr x) ),
( FSLIT("INFO_PTR"), \ [x] -> closureInfoPtr x ),
( FSLIT("STD_INFO"), \ [x] -> infoTable x ),
( FSLIT("FUN_INFO"), \ [x] -> funInfoTable x ),
( FSLIT("GET_ENTRY"), \ [x] -> entryCode (closureInfoPtr x) ),
( FSLIT("GET_STD_INFO"), \ [x] -> infoTable (closureInfoPtr x) ),
( FSLIT("GET_FUN_INFO"), \ [x] -> funInfoTable (closureInfoPtr x) ),
( FSLIT("INFO_TYPE"), \ [x] -> infoTableClosureType x ),
......
......@@ -409,12 +409,12 @@ genApply regstatus args =
vcat (do_assert args 1),
text "again:",
text "info = %GET_STD_INFO(R1);",
text "info = %INFO_PTR(R1);",
-- if fast == 1:
-- print " goto *lbls[info->type];";
-- else:
text "switch [INVALID_OBJECT .. N_CLOSURE_TYPES] (%INFO_TYPE(info)) {",
text "switch [INVALID_OBJECT .. N_CLOSURE_TYPES] (%INFO_TYPE(%STD_INFO(info))) {",
nest 4 (vcat [
-- if fast == 1:
......@@ -441,7 +441,7 @@ genApply regstatus args =
text " FUN_0_2,",
text " FUN_STATIC: {",
nest 4 (vcat [
text "arity = TO_W_(StgFunInfoExtra_arity(%GET_FUN_INFO(R1)));",
text "arity = TO_W_(StgFunInfoExtra_arity(%FUN_INFO(info)));",
text "ASSERT(arity > 0);",
genMkPAP regstatus "BUILD_PAP" "%GET_ENTRY(R1)" "FUN" "FUN"
False{-reg apply-} False{-args on stack-} False{-not a PAP-}
......@@ -485,7 +485,11 @@ genApply regstatus args =
nest 4 (vcat [
text "TICK_SLOW_CALL_UNEVALD(" <> int (length args) <> text ");",
text "Sp(0) = " <> fun_info_label <> text ";",
text "jump %GET_ENTRY(R1);",
-- CAREFUL! in SMP mode, the info table may already have been
-- overwritten by an indirection, so we must enter the original
-- info pointer we read, don't read it again, because it might
-- not be enterable any more.
text "jump %ENTRY_CODE(info);",
text ""
]),
text "}",
......
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