[llvm] r326763 - Updated docs in CrashRecoveryContext.h
Serge Pavlov via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 5 20:00:31 PST 2018
Author: sepavloff
Date: Mon Mar 5 20:00:30 2018
New Revision: 326763
URL: http://llvm.org/viewvc/llvm-project?rev=326763&view=rev
Log:
Updated docs in CrashRecoveryContext.h
Differential Revision: https://reviews.llvm.org/D43200
Modified:
llvm/trunk/include/llvm/Support/CrashRecoveryContext.h
Modified: llvm/trunk/include/llvm/Support/CrashRecoveryContext.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/CrashRecoveryContext.h?rev=326763&r1=326762&r2=326763&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Support/CrashRecoveryContext.h (original)
+++ llvm/trunk/include/llvm/Support/CrashRecoveryContext.h Mon Mar 5 20:00:30 2018
@@ -15,7 +15,7 @@
namespace llvm {
class CrashRecoveryContextCleanup;
-/// \brief Crash recovery helper object.
+/// Crash recovery helper object.
///
/// This class implements support for running operations in a safe context so
/// that crashes (memory errors, stack overflow, assertion violations) can be
@@ -27,6 +27,7 @@ class CrashRecoveryContextCleanup;
/// CrashRecoveryContext::Enable(), and then executing unsafe operations via a
/// CrashRecoveryContext object. For example:
///
+/// \code
/// void actual_work(void *);
///
/// void foo() {
@@ -38,6 +39,11 @@ class CrashRecoveryContextCleanup;
///
/// ... no crash was detected ...
/// }
+/// \endcode
+///
+/// To assist recovery the class allows specifying set of actions that will be
+/// executed in any case, whether crash occurs or not. These actions may be used
+/// to reclaim resources in the case of crash.
class CrashRecoveryContext {
void *Impl;
CrashRecoveryContextCleanup *head;
@@ -46,24 +52,27 @@ public:
CrashRecoveryContext() : Impl(nullptr), head(nullptr) {}
~CrashRecoveryContext();
+ /// Register cleanup handler, which is used when the recovery context is
+ /// finished.
+ /// The recovery context owns the the handler.
void registerCleanup(CrashRecoveryContextCleanup *cleanup);
+
void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
- /// \brief Enable crash recovery.
+ /// Enable crash recovery.
static void Enable();
- /// \brief Disable crash recovery.
+ /// Disable crash recovery.
static void Disable();
- /// \brief Return the active context, if the code is currently executing in a
+ /// Return the active context, if the code is currently executing in a
/// thread which is in a protected context.
static CrashRecoveryContext *GetCurrent();
- /// \brief Return true if the current thread is recovering from a
- /// crash.
+ /// Return true if the current thread is recovering from a crash.
static bool isRecoveringFromCrash();
- /// \brief Execute the provide callback function (with the given arguments) in
+ /// Execute the provided callback function (with the given arguments) in
/// a protected context.
///
/// \return True if the function completed successfully, and false if the
@@ -75,7 +84,7 @@ public:
return RunSafely([&]() { Fn(UserData); });
}
- /// \brief Execute the provide callback function (with the given arguments) in
+ /// Execute the provide callback function (with the given arguments) in
/// a protected context which is run in another thread (optionally with a
/// requested stack size).
///
@@ -89,11 +98,18 @@ public:
return RunSafelyOnThread([&]() { Fn(UserData); }, RequestedStackSize);
}
- /// \brief Explicitly trigger a crash recovery in the current process, and
+ /// Explicitly trigger a crash recovery in the current process, and
/// return failure from RunSafely(). This function does not return.
void HandleCrash();
};
+/// Abstract base class of cleanup handlers.
+///
+/// Derived classes override method recoverResources, which makes actual work on
+/// resource recovery.
+///
+/// Cleanup handlers are stored in a double list, which is owned and managed by
+/// a crash recovery context.
class CrashRecoveryContextCleanup {
protected:
CrashRecoveryContext *context;
@@ -115,7 +131,18 @@ private:
CrashRecoveryContextCleanup *prev, *next;
};
-template<typename DERIVED, typename T>
+/// Base class of cleanup handler that controls recovery of resources of the
+/// given type.
+///
+/// \tparam Derived Class that uses this class as a base.
+/// \tparam T Type of controlled resource.
+///
+/// This class serves as a base for its template parameter as implied by
+/// Curiously Recurring Template Pattern.
+///
+/// This class factors out creation of a cleanup handler. The latter requires
+/// knowledge of the current recovery context, which is provided by this class.
+template<typename Derived, typename T>
class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
protected:
T *resource;
@@ -123,15 +150,20 @@ protected:
: CrashRecoveryContextCleanup(context), resource(resource) {}
public:
- static DERIVED *create(T *x) {
+ /// Creates cleanup handler.
+ /// \param x Pointer to the resource recovered by this handler.
+ /// \return New handler or null if the method was called outside a recovery
+ /// context.
+ static Derived *create(T *x) {
if (x) {
if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
- return new DERIVED(context, x);
+ return new Derived(context, x);
}
return nullptr;
}
};
+/// Cleanup handler that reclaims resource by calling destructor on it.
template <typename T>
class CrashRecoveryContextDestructorCleanup : public
CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
@@ -146,6 +178,7 @@ public:
}
};
+/// Cleanup handler that reclaims resource by calling 'delete' on it.
template <typename T>
class CrashRecoveryContextDeleteCleanup : public
CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
@@ -157,10 +190,10 @@ public:
void recoverResources() override { delete this->resource; }
};
+/// Cleanup handler that reclaims resource by calling its method 'Release'.
template <typename T>
class CrashRecoveryContextReleaseRefCleanup : public
- CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T>
-{
+ CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T> {
public:
CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
T *resource)
@@ -170,6 +203,37 @@ public:
void recoverResources() override { this->resource->Release(); }
};
+/// Helper class for managing resource cleanups.
+///
+/// \tparam T Type of resource been reclaimed.
+/// \tparam Cleanup Class that defines how the resource is reclaimed.
+///
+/// Clients create objects of this type in the code executed in a crash recovery
+/// context to ensure that the resource will be reclaimed even in the case of
+/// crash. For example:
+///
+/// \code
+/// void actual_work(void *) {
+/// ...
+/// std::unique_ptr<Resource> R(new Resource());
+/// CrashRecoveryContextCleanupRegistrar D(R.get());
+/// ...
+/// }
+///
+/// void foo() {
+/// CrashRecoveryContext CRC;
+///
+/// if (!CRC.RunSafely(actual_work, 0)) {
+/// ... a crash was detected, report error to user ...
+/// }
+/// \endcode
+///
+/// If the code of `actual_work` in the example above does not crash, the
+/// destructor of CrashRecoveryContextCleanupRegistrar removes cleanup code from
+/// the current CrashRecoveryContext and the resource is reclaimed by the
+/// destructor of std::unique_ptr. If crash happens, destructors are not called
+/// and the resource is reclaimed by cleanup object registered in the recovery
+/// context by the constructor of CrashRecoveryContextCleanupRegistrar.
template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
class CrashRecoveryContextCleanupRegistrar {
CrashRecoveryContextCleanup *cleanup;
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