diff options
Diffstat (limited to 'compiler/semthreads.nim')
| -rw-r--r-- | compiler/semthreads.nim | 57 |
1 files changed, 34 insertions, 23 deletions
diff --git a/compiler/semthreads.nim b/compiler/semthreads.nim index 3ca52fc30..bff8823b2 100644 --- a/compiler/semthreads.nim +++ b/compiler/semthreads.nim @@ -18,7 +18,7 @@ ## The only crucial operation that can violate the heap invariants is the ## write access. The analysis needs to distinguish between 'unknown', 'mine', ## and 'theirs' memory and pointers. Assignments 'whatever <- unknown' are -## invalid, and so are 'theirs <- mine' but not 'mine <- theirs'. Since +## invalid, and so are 'theirs <- whatever' but not 'mine <- theirs'. Since ## strings and sequences are heap allocated they are affected too: ## ## .. code-block:: nimrod @@ -30,8 +30,9 @@ ## If the type system would distinguish between 'ref' and '!ref' and threads ## could not have '!ref' as input parameters the analysis could simply need to ## reject any write access to a global variable which contains GC'ed data. -## However, '!ref' is not implemented yet and this scheme would be too -## restrictive anyway. +## Thanks to the write barrier of the GC, this is exactly what needs to be +## done! Every write access to a global that contains GC'ed data needs to +## be prevented! Unfortunately '!ref' is not implemented yet... ## ## The assignment target is essential for the algorithm: only ## write access to heap locations and global variables are critical and need @@ -42,7 +43,8 @@ ## ## var x = globalVar # 'x' points to 'theirs' ## while true: -## globalVar = x # OK: 'theirs <- theirs' +## globalVar = x # NOT OK: 'theirs <- theirs' invalid due to +## # write barrier! ## x = "new string" # ugh: 'x is toUnknown'! ## ## --> Solution: toUnknown is never allowed anywhere! @@ -106,10 +108,12 @@ proc analyseSym(c: PProcCtx, n: PNode): TThreadOwner = if result != toUndefined: return case v.kind of skVar: + result = toNil if sfGlobal in v.flags: - result = if sfThreadVar in v.flags: toMine else: toTheirs - else: - result = toNil + if sfThreadVar in v.flags: + result = toMine + elif containsTyRef(v.typ): + result = toTheirs of skTemp, skForVar: result = toNil of skConst: result = toMine of skParam: @@ -136,7 +140,8 @@ proc writeAccess(c: PProcCtx, n: PNode, owner: TThreadOwner) = of toNil: c.mapping[v.id] = owner # fine, toNil can be overwritten of toVoid, toUndefined: InternalError(n.info, "writeAccess") - of toTheirs, toMine: + of toTheirs: Message(n.info, warnWriteToForeignHeap) + of toMine: if lastOwner != owner and owner != toNil: Message(n.info, warnDifferentHeaps) else: @@ -145,7 +150,8 @@ proc writeAccess(c: PProcCtx, n: PNode, owner: TThreadOwner) = case lastOwner of toNil: nil # fine, toNil can be overwritten of toVoid, toUndefined: InternalError(n.info, "writeAccess") - of toTheirs, toMine: + of toTheirs: Message(n.info, warnWriteToForeignHeap) + of toMine: if lastOwner != owner and owner != toNil: Message(n.info, warnDifferentHeaps) @@ -171,7 +177,8 @@ proc analyseCall(c: PProcCtx, n: PNode): TThreadOwner = newCtx.mapping[formal.id] = call.args[i-1] pushInfoContext(n.info) result = analyse(newCtx, prc.ast.sons[codePos]) - if prc.ast.sons[codePos].kind == nkEmpty and sfNoSideEffect notin prc.flags: + if prc.ast.sons[codePos].kind == nkEmpty and + {sfNoSideEffect, sfThread} * prc.flags == {}: Message(n.info, warnAnalysisLoophole, renderTree(n)) if prc.typ.sons[0] != nil: if prc.ast.len > resultPos: @@ -228,7 +235,7 @@ proc analyseArgs(c: PProcCtx, n: PNode, start = 1) = proc analyseOp(c: PProcCtx, n: PNode): TThreadOwner = if n[0].kind != nkSym or n[0].sym.kind != skProc: - if tfNoSideEffect notin n[0].typ.flags: + if {tfNoSideEffect, tfThread} * n[0].typ.flags == {}: Message(n.info, warnAnalysisLoophole, renderTree(n)) result = toNil else: @@ -335,22 +342,26 @@ proc analyse(c: PProcCtx, n: PNode): TThreadOwner = result = toVoid else: InternalError(n.info, "analysis not implemented for: " & $n.kind) -proc analyseThreadCreationCall(n: PNode) = - # thread proc is second param of ``createThread``: - if n[2].kind != nkSym or n[2].sym.kind != skProc: - Message(n.info, warnAnalysisLoophole, renderTree(n)) - return - var prc = n[2].sym +proc analyseThreadProc*(prc: PSym) = var c = newProcCtx(prc) - var formal = skipTypes(prc.typ, abstractInst).n.sons[1].sym - c.mapping[formal.id] = toTheirs # thread receives foreign data! + var formals = skipTypes(prc.typ, abstractInst).n + for i in 1 .. formals.len-1: + var formal = formals.sons[i].sym + c.mapping[formal.id] = toTheirs # thread receives foreign data! discard analyse(c, prc.ast.sons[codePos]) +when false: + proc analyseThreadCreationCall(n: PNode) = + # thread proc is second param of ``createThread``: + if n[2].kind != nkSym or n[2].sym.kind != skProc: + Message(n.info, warnAnalysisLoophole, renderTree(n)) + return + analyseProc(n[2].sym) + + proc AnalyseThread*(threadCreation: PNode) = + analyseThreadCreationCall(threadCreation) + proc needsGlobalAnalysis*: bool = result = gGlobalOptions * {optThreads, optThreadAnalysis} == {optThreads, optThreadAnalysis} -proc AnalyseThread*(threadCreation: PNode) = - if needsGlobalAnalysis(): - analyseThreadCreationCall(threadCreation) - |