maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/clang/lib/Analysis/ThreadSafety.cpp

800 lines
30 KiB
C++
Raw Blame History

//===- ThreadSafety.cpp ----------------------------------------*- C++ --*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// A intra-procedural analysis for thread safety (e.g. deadlocks and race
// conditions), based off of an annotation system.
//
// See http://clang.llvm.org/docs/LanguageExtensions.html#threadsafety for more
// information.
//
//===----------------------------------------------------------------------===//
#include "clang/Analysis/Analyses/ThreadSafety.h"
#include "clang/Analysis/AnalysisContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/CFGStmtMap.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/StmtCXX.h"
#include "clang/AST/StmtVisitor.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/SourceLocation.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/ImmutableMap.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include <algorithm>
#include <vector>
using namespace clang;
using namespace thread_safety;
// Key method definition
ThreadSafetyHandler::~ThreadSafetyHandler() {}
// Helper function
static Expr *getParent(Expr *Exp) {
if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp))
return ME->getBase();
if (CXXMemberCallExpr *CE = dyn_cast<CXXMemberCallExpr>(Exp))
return CE->getImplicitObjectArgument();
return 0;
}
namespace {
/// \brief Implements a set of CFGBlocks using a BitVector.
///
/// This class contains a minimal interface, primarily dictated by the SetType
/// template parameter of the llvm::po_iterator template, as used with external
/// storage. We also use this set to keep track of which CFGBlocks we visit
/// during the analysis.
class CFGBlockSet {
llvm::BitVector VisitedBlockIDs;
public:
// po_iterator requires this iterator, but the only interface needed is the
// value_type typedef.
struct iterator {
typedef const CFGBlock *value_type;
};
CFGBlockSet() {}
CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {}
/// \brief Set the bit associated with a particular CFGBlock.
/// This is the important method for the SetType template parameter.
bool insert(const CFGBlock *Block) {
// Note that insert() is called by po_iterator, which doesn't check to make
// sure that Block is non-null. Moreover, the CFGBlock iterator will
// occasionally hand out null pointers for pruned edges, so we catch those
// here.
if (Block == 0)
return false; // if an edge is trivially false.
if (VisitedBlockIDs.test(Block->getBlockID()))
return false;
VisitedBlockIDs.set(Block->getBlockID());
return true;
}
/// \brief Check if the bit for a CFGBlock has been already set.
/// This method is for tracking visited blocks in the main threadsafety loop.
/// Block must not be null.
bool alreadySet(const CFGBlock *Block) {
return VisitedBlockIDs.test(Block->getBlockID());
}
};
/// \brief We create a helper class which we use to iterate through CFGBlocks in
/// the topological order.
class TopologicallySortedCFG {
typedef llvm::po_iterator<const CFG*, CFGBlockSet, true> po_iterator;
std::vector<const CFGBlock*> Blocks;
public:
typedef std::vector<const CFGBlock*>::reverse_iterator iterator;
TopologicallySortedCFG(const CFG *CFGraph) {
Blocks.reserve(CFGraph->getNumBlockIDs());
CFGBlockSet BSet(CFGraph);
for (po_iterator I = po_iterator::begin(CFGraph, BSet),
E = po_iterator::end(CFGraph, BSet); I != E; ++I) {
Blocks.push_back(*I);
}
}
iterator begin() {
return Blocks.rbegin();
}
iterator end() {
return Blocks.rend();
}
bool empty() {
return begin() == end();
}
};
/// \brief A MutexID object uniquely identifies a particular mutex, and
/// is built from an Expr* (i.e. calling a lock function).
///
/// Thread-safety analysis works by comparing lock expressions. Within the
/// body of a function, an expression such as "x->foo->bar.mu" will resolve to
/// a particular mutex object at run-time. Subsequent occurrences of the same
/// expression (where "same" means syntactic equality) will refer to the same
/// run-time object if three conditions hold:
/// (1) Local variables in the expression, such as "x" have not changed.
/// (2) Values on the heap that affect the expression have not changed.
/// (3) The expression involves only pure function calls.
/// The current implementation assumes, but does not verify, that multiple uses
/// of the same lock expression satisfies these criteria.
///
/// Clang introduces an additional wrinkle, which is that it is difficult to
/// derive canonical expressions, or compare expressions directly for equality.
/// Thus, we identify a mutex not by an Expr, but by the set of named
/// declarations that are referenced by the Expr. In other words,
/// x->foo->bar.mu will be a four element vector with the Decls for
/// mu, bar, and foo, and x. The vector will uniquely identify the expression
/// for all practical purposes.
///
/// Note we will need to perform substitution on "this" and function parameter
/// names when constructing a lock expression.
///
/// For example:
/// class C { Mutex Mu; void lock() EXCLUSIVE_LOCK_FUNCTION(this->Mu); };
/// void myFunc(C *X) { ... X->lock() ... }
/// The original expression for the mutex acquired by myFunc is "this->Mu", but
/// "X" is substituted for "this" so we get X->Mu();
///
/// For another example:
/// foo(MyList *L) EXCLUSIVE_LOCKS_REQUIRED(L->Mu) { ... }
/// MyList *MyL;
/// foo(MyL); // requires lock MyL->Mu to be held
class MutexID {
SmallVector<NamedDecl*, 2> DeclSeq;
/// Build a Decl sequence representing the lock from the given expression.
/// Recursive function that bottoms out when the final DeclRefExpr is reached.
// FIXME: Lock expressions that involve array indices or function calls.
// FIXME: Deal with LockReturned attribute.
void buildMutexID(Expr *Exp, Expr *Parent) {
if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Exp)) {
NamedDecl *ND = cast<NamedDecl>(DRE->getDecl()->getCanonicalDecl());
DeclSeq.push_back(ND);
} else if (MemberExpr *ME = dyn_cast<MemberExpr>(Exp)) {
NamedDecl *ND = ME->getMemberDecl();
DeclSeq.push_back(ND);
buildMutexID(ME->getBase(), Parent);
} else if (isa<CXXThisExpr>(Exp)) {
if (Parent)
buildMutexID(Parent, 0);
else
return; // mutexID is still valid in this case
} else if (CastExpr *CE = dyn_cast<CastExpr>(Exp))
buildMutexID(CE->getSubExpr(), Parent);
else
DeclSeq.clear(); // invalid lock expression
}
public:
MutexID(Expr *LExpr, Expr *ParentExpr) {
buildMutexID(LExpr, ParentExpr);
}
/// If we encounter part of a lock expression we cannot parse
bool isValid() const {
return !DeclSeq.empty();
}
bool operator==(const MutexID &other) const {
return DeclSeq == other.DeclSeq;
}
bool operator!=(const MutexID &other) const {
return !(*this == other);
}
// SmallVector overloads Operator< to do lexicographic ordering. Note that
// we use pointer equality (and <) to compare NamedDecls. This means the order
// of MutexIDs in a lockset is nondeterministic. In order to output
// diagnostics in a deterministic ordering, we must order all diagnostics to
// output by SourceLocation when iterating through this lockset.
bool operator<(const MutexID &other) const {
return DeclSeq < other.DeclSeq;
}
/// \brief Returns the name of the first Decl in the list for a given MutexID;
/// e.g. the lock expression foo.bar() has name "bar".
/// The caret will point unambiguously to the lock expression, so using this
/// name in diagnostics is a way to get simple, and consistent, mutex names.
/// We do not want to output the entire expression text for security reasons.
StringRef getName() const {
assert(isValid());
return DeclSeq.front()->getName();
}
void Profile(llvm::FoldingSetNodeID &ID) const {
for (SmallVectorImpl<NamedDecl*>::const_iterator I = DeclSeq.begin(),
E = DeclSeq.end(); I != E; ++I) {
ID.AddPointer(*I);
}
}
};
/// \brief This is a helper class that stores info about the most recent
/// accquire of a Lock.
///
/// The main body of the analysis maps MutexIDs to LockDatas.
struct LockData {
SourceLocation AcquireLoc;
/// \brief LKind stores whether a lock is held shared or exclusively.
/// Note that this analysis does not currently support either re-entrant
/// locking or lock "upgrading" and "downgrading" between exclusive and
/// shared.
///
/// FIXME: add support for re-entrant locking and lock up/downgrading
LockKind LKind;
LockData(SourceLocation AcquireLoc, LockKind LKind)
: AcquireLoc(AcquireLoc), LKind(LKind) {}
bool operator==(const LockData &other) const {
return AcquireLoc == other.AcquireLoc && LKind == other.LKind;
}
bool operator!=(const LockData &other) const {
return !(*this == other);
}
void Profile(llvm::FoldingSetNodeID &ID) const {
ID.AddInteger(AcquireLoc.getRawEncoding());
ID.AddInteger(LKind);
}
};
/// A Lockset maps each MutexID (defined above) to information about how it has
/// been locked.
typedef llvm::ImmutableMap<MutexID, LockData> Lockset;
/// \brief We use this class to visit different types of expressions in
/// CFGBlocks, and build up the lockset.
/// An expression may cause us to add or remove locks from the lockset, or else
/// output error messages related to missing locks.
/// FIXME: In future, we may be able to not inherit from a visitor.
class BuildLockset : public StmtVisitor<BuildLockset> {
ThreadSafetyHandler &Handler;
Lockset LSet;
Lockset::Factory &LocksetFactory;
// Helper functions
void removeLock(SourceLocation UnlockLoc, Expr *LockExp, Expr *Parent);
void addLock(SourceLocation LockLoc, Expr *LockExp, Expr *Parent,
LockKind LK);
const ValueDecl *getValueDecl(Expr *Exp);
void warnIfMutexNotHeld (const NamedDecl *D, Expr *Exp, AccessKind AK,
Expr *MutexExp, ProtectedOperationKind POK);
void checkAccess(Expr *Exp, AccessKind AK);
void checkDereference(Expr *Exp, AccessKind AK);
template <class AttrType>
void addLocksToSet(LockKind LK, Attr *Attr, CXXMemberCallExpr *Exp);
/// \brief Returns true if the lockset contains a lock, regardless of whether
/// the lock is held exclusively or shared.
bool locksetContains(MutexID Lock) const {
return LSet.lookup(Lock);
}
/// \brief Returns true if the lockset contains a lock with the passed in
/// locktype.
bool locksetContains(MutexID Lock, LockKind KindRequested) const {
const LockData *LockHeld = LSet.lookup(Lock);
return (LockHeld && KindRequested == LockHeld->LKind);
}
/// \brief Returns true if the lockset contains a lock with at least the
/// passed in locktype. So for example, if we pass in LK_Shared, this function
/// returns true if the lock is held LK_Shared or LK_Exclusive. If we pass in
/// LK_Exclusive, this function returns true if the lock is held LK_Exclusive.
bool locksetContainsAtLeast(MutexID Lock, LockKind KindRequested) const {
switch (KindRequested) {
case LK_Shared:
return locksetContains(Lock);
case LK_Exclusive:
return locksetContains(Lock, KindRequested);
}
llvm_unreachable("Unknown LockKind");
}
public:
BuildLockset(ThreadSafetyHandler &Handler, Lockset LS, Lockset::Factory &F)
: StmtVisitor<BuildLockset>(), Handler(Handler), LSet(LS),
LocksetFactory(F) {}
Lockset getLockset() {
return LSet;
}
void VisitUnaryOperator(UnaryOperator *UO);
void VisitBinaryOperator(BinaryOperator *BO);
void VisitCastExpr(CastExpr *CE);
void VisitCXXMemberCallExpr(CXXMemberCallExpr *Exp);
};
/// \brief Add a new lock to the lockset, warning if the lock is already there.
/// \param LockLoc The source location of the acquire
/// \param LockExp The lock expression corresponding to the lock to be added
void BuildLockset::addLock(SourceLocation LockLoc, Expr *LockExp, Expr *Parent,
LockKind LK) {
// FIXME: deal with acquired before/after annotations. We can write a first
// pass that does the transitive lookup lazily, and refine afterwards.
MutexID Mutex(LockExp, Parent);
if (!Mutex.isValid()) {
Handler.handleInvalidLockExp(LockExp->getExprLoc());
return;
}
LockData NewLock(LockLoc, LK);
// FIXME: Don't always warn when we have support for reentrant locks.
if (locksetContains(Mutex))
Handler.handleDoubleLock(Mutex.getName(), LockLoc);
LSet = LocksetFactory.add(LSet, Mutex, NewLock);
}
/// \brief Remove a lock from the lockset, warning if the lock is not there.
/// \param LockExp The lock expression corresponding to the lock to be removed
/// \param UnlockLoc The source location of the unlock (only used in error msg)
void BuildLockset::removeLock(SourceLocation UnlockLoc, Expr *LockExp,
Expr *Parent) {
MutexID Mutex(LockExp, Parent);
if (!Mutex.isValid()) {
Handler.handleInvalidLockExp(LockExp->getExprLoc());
return;
}
Lockset NewLSet = LocksetFactory.remove(LSet, Mutex);
if(NewLSet == LSet)
Handler.handleUnmatchedUnlock(Mutex.getName(), UnlockLoc);
LSet = NewLSet;
}
/// \brief Gets the value decl pointer from DeclRefExprs or MemberExprs
const ValueDecl *BuildLockset::getValueDecl(Expr *Exp) {
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Exp))
return DR->getDecl();
if (const MemberExpr *ME = dyn_cast<MemberExpr>(Exp))
return ME->getMemberDecl();
return 0;
}
/// \brief Warn if the LSet does not contain a lock sufficient to protect access
/// of at least the passed in AccessType.
void BuildLockset::warnIfMutexNotHeld(const NamedDecl *D, Expr *Exp,
AccessKind AK, Expr *MutexExp,
ProtectedOperationKind POK) {
LockKind LK = getLockKindFromAccessKind(AK);
Expr *Parent = getParent(Exp);
MutexID Mutex(MutexExp, Parent);
if (!Mutex.isValid())
Handler.handleInvalidLockExp(MutexExp->getExprLoc());
else if (!locksetContainsAtLeast(Mutex, LK))
Handler.handleMutexNotHeld(D, POK, Mutex.getName(), LK, Exp->getExprLoc());
}
/// \brief This method identifies variable dereferences and checks pt_guarded_by
/// and pt_guarded_var annotations. Note that we only check these annotations
/// at the time a pointer is dereferenced.
/// FIXME: We need to check for other types of pointer dereferences
/// (e.g. [], ->) and deal with them here.
/// \param Exp An expression that has been read or written.
void BuildLockset::checkDereference(Expr *Exp, AccessKind AK) {
UnaryOperator *UO = dyn_cast<UnaryOperator>(Exp);
if (!UO || UO->getOpcode() != clang::UO_Deref)
return;
Exp = UO->getSubExpr()->IgnoreParenCasts();
const ValueDecl *D = getValueDecl(Exp);
if(!D || !D->hasAttrs())
return;
if (D->getAttr<PtGuardedVarAttr>() && LSet.isEmpty())
Handler.handleNoMutexHeld(D, POK_VarDereference, AK, Exp->getExprLoc());
const AttrVec &ArgAttrs = D->getAttrs();
for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i)
if (PtGuardedByAttr *PGBAttr = dyn_cast<PtGuardedByAttr>(ArgAttrs[i]))
warnIfMutexNotHeld(D, Exp, AK, PGBAttr->getArg(), POK_VarDereference);
}
/// \brief Checks guarded_by and guarded_var attributes.
/// Whenever we identify an access (read or write) of a DeclRefExpr or
/// MemberExpr, we need to check whether there are any guarded_by or
/// guarded_var attributes, and make sure we hold the appropriate mutexes.
void BuildLockset::checkAccess(Expr *Exp, AccessKind AK) {
const ValueDecl *D = getValueDecl(Exp);
if(!D || !D->hasAttrs())
return;
if (D->getAttr<GuardedVarAttr>() && LSet.isEmpty())
Handler.handleNoMutexHeld(D, POK_VarAccess, AK, Exp->getExprLoc());
const AttrVec &ArgAttrs = D->getAttrs();
for(unsigned i = 0, Size = ArgAttrs.size(); i < Size; ++i)
if (GuardedByAttr *GBAttr = dyn_cast<GuardedByAttr>(ArgAttrs[i]))
warnIfMutexNotHeld(D, Exp, AK, GBAttr->getArg(), POK_VarAccess);
}
/// \brief For unary operations which read and write a variable, we need to
/// check whether we hold any required mutexes. Reads are checked in
/// VisitCastExpr.
void BuildLockset::VisitUnaryOperator(UnaryOperator *UO) {
switch (UO->getOpcode()) {
case clang::UO_PostDec:
case clang::UO_PostInc:
case clang::UO_PreDec:
case clang::UO_PreInc: {
Expr *SubExp = UO->getSubExpr()->IgnoreParenCasts();
checkAccess(SubExp, AK_Written);
checkDereference(SubExp, AK_Written);
break;
}
default:
break;
}
}
/// For binary operations which assign to a variable (writes), we need to check
/// whether we hold any required mutexes.
/// FIXME: Deal with non-primitive types.
void BuildLockset::VisitBinaryOperator(BinaryOperator *BO) {
if (!BO->isAssignmentOp())
return;
Expr *LHSExp = BO->getLHS()->IgnoreParenCasts();
checkAccess(LHSExp, AK_Written);
checkDereference(LHSExp, AK_Written);
}
/// Whenever we do an LValue to Rvalue cast, we are reading a variable and
/// need to ensure we hold any required mutexes.
/// FIXME: Deal with non-primitive types.
void BuildLockset::VisitCastExpr(CastExpr *CE) {
if (CE->getCastKind() != CK_LValueToRValue)
return;
Expr *SubExp = CE->getSubExpr()->IgnoreParenCasts();
checkAccess(SubExp, AK_Read);
checkDereference(SubExp, AK_Read);
}
/// \brief This function, parameterized by an attribute type, is used to add a
/// set of locks specified as attribute arguments to the lockset.
template <typename AttrType>
void BuildLockset::addLocksToSet(LockKind LK, Attr *Attr,
CXXMemberCallExpr *Exp) {
typedef typename AttrType::args_iterator iterator_type;
SourceLocation ExpLocation = Exp->getExprLoc();
Expr *Parent = Exp->getImplicitObjectArgument();
AttrType *SpecificAttr = cast<AttrType>(Attr);
if (SpecificAttr->args_size() == 0) {
// The mutex held is the "this" object.
addLock(ExpLocation, Parent, 0, LK);
return;
}
for (iterator_type I = SpecificAttr->args_begin(),
E = SpecificAttr->args_end(); I != E; ++I)
addLock(ExpLocation, *I, Parent, LK);
}
/// \brief When visiting CXXMemberCallExprs we need to examine the attributes on
/// the method that is being called and add, remove or check locks in the
/// lockset accordingly.
///
/// FIXME: For classes annotated with one of the guarded annotations, we need
/// to treat const method calls as reads and non-const method calls as writes,
/// and check that the appropriate locks are held. Non-const method calls with
/// the same signature as const method calls can be also treated as reads.
///
/// FIXME: We need to also visit CallExprs to catch/check global functions.
///
/// FIXME: Do not flag an error for member variables accessed in constructors/
/// destructors
void BuildLockset::VisitCXXMemberCallExpr(CXXMemberCallExpr *Exp) {
NamedDecl *D = dyn_cast_or_null<NamedDecl>(Exp->getCalleeDecl());
SourceLocation ExpLocation = Exp->getExprLoc();
Expr *Parent = Exp->getImplicitObjectArgument();
if(!D || !D->hasAttrs())
return;
AttrVec &ArgAttrs = D->getAttrs();
for(unsigned i = 0; i < ArgAttrs.size(); ++i) {
Attr *Attr = ArgAttrs[i];
switch (Attr->getKind()) {
// When we encounter an exclusive lock function, we need to add the lock
// to our lockset with kind exclusive.
case attr::ExclusiveLockFunction:
addLocksToSet<ExclusiveLockFunctionAttr>(LK_Exclusive, Attr, Exp);
break;
// When we encounter a shared lock function, we need to add the lock
// to our lockset with kind shared.
case attr::SharedLockFunction:
addLocksToSet<SharedLockFunctionAttr>(LK_Shared, Attr, Exp);
break;
// When we encounter an unlock function, we need to remove unlocked
// mutexes from the lockset, and flag a warning if they are not there.
case attr::UnlockFunction: {
UnlockFunctionAttr *UFAttr = cast<UnlockFunctionAttr>(Attr);
if (UFAttr->args_size() == 0) { // The lock held is the "this" object.
removeLock(ExpLocation, Parent, 0);
break;
}
for (UnlockFunctionAttr::args_iterator I = UFAttr->args_begin(),
E = UFAttr->args_end(); I != E; ++I)
removeLock(ExpLocation, *I, Parent);
break;
}
case attr::ExclusiveLocksRequired: {
ExclusiveLocksRequiredAttr *ELRAttr =
cast<ExclusiveLocksRequiredAttr>(Attr);
for (ExclusiveLocksRequiredAttr::args_iterator
I = ELRAttr->args_begin(), E = ELRAttr->args_end(); I != E; ++I)
warnIfMutexNotHeld(D, Exp, AK_Written, *I, POK_FunctionCall);
break;
}
case attr::SharedLocksRequired: {
SharedLocksRequiredAttr *SLRAttr = cast<SharedLocksRequiredAttr>(Attr);
for (SharedLocksRequiredAttr::args_iterator I = SLRAttr->args_begin(),
E = SLRAttr->args_end(); I != E; ++I)
warnIfMutexNotHeld(D, Exp, AK_Read, *I, POK_FunctionCall);
break;
}
case attr::LocksExcluded: {
LocksExcludedAttr *LEAttr = cast<LocksExcludedAttr>(Attr);
for (LocksExcludedAttr::args_iterator I = LEAttr->args_begin(),
E = LEAttr->args_end(); I != E; ++I) {
MutexID Mutex(*I, Parent);
if (!Mutex.isValid())
Handler.handleInvalidLockExp((*I)->getExprLoc());
else if (locksetContains(Mutex))
Handler.handleFunExcludesLock(D->getName(), Mutex.getName(),
ExpLocation);
}
break;
}
// Ignore other (non thread-safety) attributes
default:
break;
}
}
}
} // end anonymous namespace
/// \brief Compute the intersection of two locksets and issue warnings for any
/// locks in the symmetric difference.
///
/// This function is used at a merge point in the CFG when comparing the lockset
/// of each branch being merged. For example, given the following sequence:
/// A; if () then B; else C; D; we need to check that the lockset after B and C
/// are the same. In the event of a difference, we use the intersection of these
/// two locksets at the start of D.
static Lockset intersectAndWarn(ThreadSafetyHandler &Handler,
const Lockset LSet1, const Lockset LSet2,
Lockset::Factory &Fact, LockErrorKind LEK) {
Lockset Intersection = LSet1;
for (Lockset::iterator I = LSet2.begin(), E = LSet2.end(); I != E; ++I) {
const MutexID &LSet2Mutex = I.getKey();
const LockData &LSet2LockData = I.getData();
if (const LockData *LD = LSet1.lookup(LSet2Mutex)) {
if (LD->LKind != LSet2LockData.LKind) {
Handler.handleExclusiveAndShared(LSet2Mutex.getName(),
LSet2LockData.AcquireLoc,
LD->AcquireLoc);
if (LD->LKind != LK_Exclusive)
Intersection = Fact.add(Intersection, LSet2Mutex, LSet2LockData);
}
} else {
Handler.handleMutexHeldEndOfScope(LSet2Mutex.getName(),
LSet2LockData.AcquireLoc, LEK);
}
}
for (Lockset::iterator I = LSet1.begin(), E = LSet1.end(); I != E; ++I) {
if (!LSet2.contains(I.getKey())) {
const MutexID &Mutex = I.getKey();
const LockData &MissingLock = I.getData();
Handler.handleMutexHeldEndOfScope(Mutex.getName(),
MissingLock.AcquireLoc, LEK);
Intersection = Fact.remove(Intersection, Mutex);
}
}
return Intersection;
}
static Lockset addLock(ThreadSafetyHandler &Handler,
Lockset::Factory &LocksetFactory,
Lockset &LSet, Expr *LockExp, LockKind LK,
SourceLocation Loc) {
MutexID Mutex(LockExp, 0);
if (!Mutex.isValid()) {
Handler.handleInvalidLockExp(LockExp->getExprLoc());
return LSet;
}
LockData NewLock(Loc, LK);
return LocksetFactory.add(LSet, Mutex, NewLock);
}
namespace clang {
namespace thread_safety {
/// \brief Check a function's CFG for thread-safety violations.
///
/// We traverse the blocks in the CFG, compute the set of mutexes that are held
/// at the end of each block, and issue warnings for thread safety violations.
/// Each block in the CFG is traversed exactly once.
void runThreadSafetyAnalysis(AnalysisContext &AC,
ThreadSafetyHandler &Handler) {
CFG *CFGraph = AC.getCFG();
if (!CFGraph) return;
const Decl *D = AC.getDecl();
if (D && D->getAttr<NoThreadSafetyAnalysisAttr>()) return;
Lockset::Factory LocksetFactory;
// FIXME: Swith to SmallVector? Otherwise improve performance impact?
std::vector<Lockset> EntryLocksets(CFGraph->getNumBlockIDs(),
LocksetFactory.getEmptyMap());
std::vector<Lockset> ExitLocksets(CFGraph->getNumBlockIDs(),
LocksetFactory.getEmptyMap());
// We need to explore the CFG via a "topological" ordering.
// That way, we will be guaranteed to have information about required
// predecessor locksets when exploring a new block.
TopologicallySortedCFG SortedGraph(CFGraph);
CFGBlockSet VisitedBlocks(CFGraph);
if (!SortedGraph.empty() && D->hasAttrs()) {
const CFGBlock *FirstBlock = *SortedGraph.begin();
Lockset &InitialLockset = EntryLocksets[FirstBlock->getBlockID()];
const AttrVec &ArgAttrs = D->getAttrs();
for(unsigned i = 0; i < ArgAttrs.size(); ++i) {
Attr *Attr = ArgAttrs[i];
SourceLocation AttrLoc = Attr->getLocation();
if (SharedLocksRequiredAttr *SLRAttr
= dyn_cast<SharedLocksRequiredAttr>(Attr)) {
for (SharedLocksRequiredAttr::args_iterator
SLRIter = SLRAttr->args_begin(),
SLREnd = SLRAttr->args_end(); SLRIter != SLREnd; ++SLRIter)
InitialLockset = addLock(Handler, LocksetFactory, InitialLockset,
*SLRIter, LK_Shared,
AttrLoc);
} else if (ExclusiveLocksRequiredAttr *ELRAttr
= dyn_cast<ExclusiveLocksRequiredAttr>(Attr)) {
for (ExclusiveLocksRequiredAttr::args_iterator
ELRIter = ELRAttr->args_begin(),
ELREnd = ELRAttr->args_end(); ELRIter != ELREnd; ++ELRIter)
InitialLockset = addLock(Handler, LocksetFactory, InitialLockset,
*ELRIter, LK_Exclusive,
AttrLoc);
}
}
}
for (TopologicallySortedCFG::iterator I = SortedGraph.begin(),
E = SortedGraph.end(); I!= E; ++I) {
const CFGBlock *CurrBlock = *I;
int CurrBlockID = CurrBlock->getBlockID();
VisitedBlocks.insert(CurrBlock);
// Use the default initial lockset in case there are no predecessors.
Lockset &Entryset = EntryLocksets[CurrBlockID];
Lockset &Exitset = ExitLocksets[CurrBlockID];
// Iterate through the predecessor blocks and warn if the lockset for all
// predecessors is not the same. We take the entry lockset of the current
// block to be the intersection of all previous locksets.
// FIXME: By keeping the intersection, we may output more errors in future
// for a lock which is not in the intersection, but was in the union. We
// may want to also keep the union in future. As an example, let's say
// the intersection contains Mutex L, and the union contains L and M.
// Later we unlock M. At this point, we would output an error because we
// never locked M; although the real error is probably that we forgot to
// lock M on all code paths. Conversely, let's say that later we lock M.
// In this case, we should compare against the intersection instead of the
// union because the real error is probably that we forgot to unlock M on
// all code paths.
bool LocksetInitialized = false;
for (CFGBlock::const_pred_iterator PI = CurrBlock->pred_begin(),
PE = CurrBlock->pred_end(); PI != PE; ++PI) {
// if *PI -> CurrBlock is a back edge
if (*PI == 0 || !VisitedBlocks.alreadySet(*PI))
continue;
int PrevBlockID = (*PI)->getBlockID();
if (!LocksetInitialized) {
Entryset = ExitLocksets[PrevBlockID];
LocksetInitialized = true;
} else {
Entryset = intersectAndWarn(Handler, Entryset,
ExitLocksets[PrevBlockID], LocksetFactory,
LEK_LockedSomePredecessors);
}
}
BuildLockset LocksetBuilder(Handler, Entryset, LocksetFactory);
for (CFGBlock::const_iterator BI = CurrBlock->begin(),
BE = CurrBlock->end(); BI != BE; ++BI) {
if (const CFGStmt *CfgStmt = dyn_cast<CFGStmt>(&*BI))
LocksetBuilder.Visit(const_cast<Stmt*>(CfgStmt->getStmt()));
}
Exitset = LocksetBuilder.getLockset();
// For every back edge from CurrBlock (the end of the loop) to another block
// (FirstLoopBlock) we need to check that the Lockset of Block is equal to
// the one held at the beginning of FirstLoopBlock. We can look up the
// Lockset held at the beginning of FirstLoopBlock in the EntryLockSets map.
for (CFGBlock::const_succ_iterator SI = CurrBlock->succ_begin(),
SE = CurrBlock->succ_end(); SI != SE; ++SI) {
// if CurrBlock -> *SI is *not* a back edge
if (*SI == 0 || !VisitedBlocks.alreadySet(*SI))
continue;
CFGBlock *FirstLoopBlock = *SI;
Lockset PreLoop = EntryLocksets[FirstLoopBlock->getBlockID()];
Lockset LoopEnd = ExitLocksets[CurrBlockID];
intersectAndWarn(Handler, LoopEnd, PreLoop, LocksetFactory,
LEK_LockedSomeLoopIterations);
}
}
Lockset InitialLockset = EntryLocksets[CFGraph->getEntry().getBlockID()];
Lockset FinalLockset = ExitLocksets[CFGraph->getExit().getBlockID()];
// FIXME: Should we call this function for all blocks which exit the function?
intersectAndWarn(Handler, InitialLockset, FinalLockset, LocksetFactory,
LEK_LockedAtEndOfFunction);
}
/// \brief Helper function that returns a LockKind required for the given level
/// of access.
LockKind getLockKindFromAccessKind(AccessKind AK) {
switch (AK) {
case AK_Read :
return LK_Shared;
case AK_Written :
return LK_Exclusive;
}
llvm_unreachable("Unknown AccessKind");
}
}} // end namespace clang::thread_safety
Reference in New Issue View Git Blame Copy Permalink