diff options
| -rw-r--r-- | includes/Cmm.h | 6 | ||||
| -rw-r--r-- | rts/sm/Storage.c | 13 | ||||
| -rw-r--r-- | utils/deriveConstants/Main.hs | 2 |
3 files changed, 16 insertions, 5 deletions
diff --git a/includes/Cmm.h b/includes/Cmm.h index 574c60a1b3..fdb4badf9a 100644 --- a/includes/Cmm.h +++ b/includes/Cmm.h @@ -630,7 +630,11 @@ #else #define OVERWRITING_CLOSURE_SIZE(c, size) /* nothing */ #define OVERWRITING_CLOSURE(c) /* nothing */ -#define OVERWRITING_CLOSURE_MUTABLE(c, off) /* nothing */ +/* This is used to zero slop after shrunk arrays. It is important that we do + * this whenever profiling is enabled as described in Note [slop on the heap] + * in Storage.c. */ +#define OVERWRITING_CLOSURE_MUTABLE(c, off) \ + if (TO_W_(RtsFlags_ProfFlags_doHeapProfile(RtsFlags)) != 0) { foreign "C" overwritingMutableClosureOfs(c "ptr", off); } #endif // Memory barriers. diff --git a/rts/sm/Storage.c b/rts/sm/Storage.c index a43719fc9b..41abbfc81c 100644 --- a/rts/sm/Storage.c +++ b/rts/sm/Storage.c @@ -953,14 +953,19 @@ accountAllocation(Capability *cap, W_ n) * profiler, see Note [skipping slop in the heap profiler]. * * In general we zero: + * * - Pinned object alignment slop, see MEMSET_SLOP_W in allocatePinned. * - Large object alignment slop, see MEMSET_SLOP_W in allocatePinned. - * This is necessary even in the vanilla RTS since the user may trigger a heap - * census via +RTS -hT even when not linking against the profiled RTS. - * - * Only when profiling we zero: * - Shrunk array slop, see OVERWRITING_CLOSURE_MUTABLE. * + * Note that this is necessary even in the vanilla (e.g. non-profiling) RTS + * since the user may trigger a heap census via +RTS -hT, which can be used + * even when not linking against the profiled RTS. Failing to zero slop + * due to array shrinking has resulted in a few nasty bugs (#17572, #9666). + * However, since array shrink may result in large amounts of slop (unlike + * alignment), we take care to only zero such slop when heap profiling or DEBUG + * are enabled. + * * When performing LDV profiling or using a (single threaded) debug RTS we zero * slop even when overwriting immutable closures, see Note [zeroing slop when * overwriting closures]. diff --git a/utils/deriveConstants/Main.hs b/utils/deriveConstants/Main.hs index 1c648d2e6f..c384a7058f 100644 --- a/utils/deriveConstants/Main.hs +++ b/utils/deriveConstants/Main.hs @@ -561,6 +561,8 @@ wanteds os = concat ,structField C "StgCompactNFDataBlock" "owner" ,structField C "StgCompactNFDataBlock" "next" + ,structField_ C "RtsFlags_ProfFlags_doHeapProfile" + "RTS_FLAGS" "ProfFlags.doHeapProfile" ,structField_ C "RtsFlags_ProfFlags_showCCSOnException" "RTS_FLAGS" "ProfFlags.showCCSOnException" ,structField_ C "RtsFlags_DebugFlags_apply" |