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/* ---------------------------------------------------------------------------
*
* (c) The GHC Team, 2020-2021
*
* Stack snapshotting and decoding. (Cloning and unwinding.)
*
*---------------------------------------------------------------------------*/
#include "Rts.h"
#include "RtsFlags.h"
#include "rts/Messages.h"
#include "Messages.h"
#include "rts/Types.h"
#include "rts/storage/TSO.h"
#include "stg/Types.h"
#include "CloneStack.h"
#include "StablePtr.h"
#include "Threads.h"
#include "Prelude.h"
#if defined(DEBUG)
#include "sm/Sanity.h"
#include "Printer.h"
#endif
#include <string.h>
static StgWord getStackFrameCount(StgStack* stack);
static StgWord getStackChunkClosureCount(StgStack* stack);
static StgArrBytes* allocateByteArray(Capability *cap, StgWord bytes);
static void copyPtrsToArray(StgArrBytes* arr, StgStack* stack);
static StgStack* cloneStackChunk(Capability* capability, const StgStack* stack)
{
StgWord spOffset = stack->sp - stack->stack;
StgWord closureSizeBytes = sizeof(StgStack) + (stack->stack_size * sizeof(StgWord));
StgStack* newStackClosure = (StgStack*) allocate(capability, ROUNDUP_BYTES_TO_WDS(closureSizeBytes));
memcpy(newStackClosure, stack, closureSizeBytes);
newStackClosure->sp = newStackClosure->stack + spOffset;
// The new stack is not on the mutable list; clear the dirty flag such that
// we don't claim that it is.
newStackClosure->dirty = 0;
#if defined(DEBUG)
checkClosure((StgClosure*) newStackClosure);
#endif
return newStackClosure;
}
StgStack* cloneStack(Capability* capability, const StgStack* stack)
{
StgStack *top_stack = cloneStackChunk(capability, stack);
StgStack *last_stack = top_stack;
while (true) {
// check whether the stack ends in an underflow frame
StgUnderflowFrame *frame = (StgUnderflowFrame *) (last_stack->stack
+ last_stack->stack_size - sizeofW(StgUnderflowFrame));
if (frame->info == &stg_stack_underflow_frame_info) {
StgStack *s = cloneStackChunk(capability, frame->next_chunk);
frame->next_chunk = s;
last_stack = s;
} else {
break;
}
}
return top_stack;
}
#if defined(THREADED_RTS)
// ThreadId# in Haskell is a StgTSO* in RTS.
void sendCloneStackMessage(StgTSO *tso, HsStablePtr mvar) {
Capability *srcCapability = rts_unsafeGetMyCapability();
MessageCloneStack *msg;
msg = (MessageCloneStack *)allocate(srcCapability, sizeofW(MessageCloneStack));
msg->tso = tso;
msg->result = (StgMVar*)deRefStablePtr(mvar);
SET_HDR_RELEASE(msg, &stg_MSG_CLONE_STACK_info, CCS_SYSTEM);
sendMessage(srcCapability, tso->cap, (Message *)msg);
}
void handleCloneStackMessage(MessageCloneStack *msg){
StgStack* newStackClosure = cloneStack(msg->tso->cap, msg->tso->stackobj);
// Lift StackSnapshot# to StackSnapshot by applying it's constructor.
// This is necessary because performTryPutMVar() puts the closure onto the
// stack for evaluation and stacks can not be evaluated (entered).
HaskellObj result = rts_apply(msg->tso->cap, StackSnapshot_constructor_closure, (HaskellObj) newStackClosure);
bool putMVarWasSuccessful = performTryPutMVar(msg->tso->cap, msg->result, result);
if(!putMVarWasSuccessful) {
barf("Can't put stack cloning result into MVar.");
}
}
#else // !defined(THREADED_RTS)
STG_NORETURN
void sendCloneStackMessage(StgTSO *tso STG_UNUSED, HsStablePtr mvar STG_UNUSED) {
barf("Sending CloneStackMessages is only available in threaded RTS!");
}
#endif // end !defined(THREADED_RTS)
// Creates a MutableArray# (Haskell representation) that contains a
// InfoProvEnt* for every stack frame on the given stack. Thus, the size of the
// array is the count of stack frames.
// Each InfoProvEnt* is looked up by lookupIPE(). If there's no IPE for a stack
// frame it's represented by null.
StgArrBytes* decodeClonedStack(Capability *cap, StgStack* stack) {
StgWord closureCount = getStackFrameCount(stack);
StgArrBytes* array = allocateByteArray(cap, sizeof(StgInfoTable*) * closureCount);
copyPtrsToArray(array, stack);
return array;
}
// Count the stack frames that are on the given stack.
// This is the sum of all stack frames in all stack chunks of this stack.
StgWord getStackFrameCount(StgStack* stack) {
StgWord closureCount = 0;
StgStack *last_stack = stack;
while (true) {
closureCount += getStackChunkClosureCount(last_stack);
// check whether the stack ends in an underflow frame
StgUnderflowFrame *frame = (StgUnderflowFrame *) (last_stack->stack
+ last_stack->stack_size - sizeofW(StgUnderflowFrame));
if (frame->info == &stg_stack_underflow_frame_info) {
last_stack = frame->next_chunk;
} else {
break;
}
}
return closureCount;
}
StgWord getStackChunkClosureCount(StgStack* stack) {
StgWord closureCount = 0;
StgPtr sp = stack->sp;
StgPtr spBottom = stack->stack + stack->stack_size;
for (; sp < spBottom; sp += stack_frame_sizeW((StgClosure *)sp)) {
closureCount++;
}
return closureCount;
}
// Allocate and initialize memory for a ByteArray# (Haskell representation).
StgArrBytes* allocateByteArray(Capability *cap, StgWord bytes) {
// Idea stolen from PrimOps.cmm:stg_newArrayzh()
StgWord words = sizeofW(StgArrBytes) + bytes;
StgArrBytes* array = (StgArrBytes*) allocate(cap, words);
SET_HDR(array, &stg_ARR_WORDS_info, CCS_SYSTEM);
array->bytes = bytes;
return array;
}
static void copyPtrsToArray(StgArrBytes* arr, StgStack* stack) {
StgWord index = 0;
StgStack *last_stack = stack;
const StgInfoTable **result = (const StgInfoTable **) arr->payload;
while (true) {
StgPtr sp = last_stack->sp;
StgPtr spBottom = last_stack->stack + last_stack->stack_size;
for (; sp < spBottom; sp += stack_frame_sizeW((StgClosure *)sp)) {
const StgInfoTable* infoTable = ((StgClosure *)sp)->header.info;
result[index] = infoTable;
index++;
}
// Ensure that we didn't overflow the result array
ASSERT(index-1 < arr->bytes / sizeof(StgInfoTable*));
// check whether the stack ends in an underflow frame
StgUnderflowFrame *frame = (StgUnderflowFrame *) (last_stack->stack
+ last_stack->stack_size - sizeofW(StgUnderflowFrame));
if (frame->info == &stg_stack_underflow_frame_info) {
last_stack = frame->next_chunk;
} else {
break;
}
}
}
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