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new da4e33a6 Support a more safe read function and variadic functions of
DoublyBufferedData (#2898)
da4e33a6 is described below
commit da4e33a6ee44d107bc0dd9632b2db289aa815cdd
Author: Bright Chen <chenguangmin...@foxmail.com>
AuthorDate: Fri Mar 21 23:42:43 2025 +0800
Support a more safe read function and variadic functions of
DoublyBufferedData (#2898)
* Add a convenient and safe DoublyBufferedData::Read
* Optimize and add a UT
* Support variadic functions of DoublyBufferedData
* Fix Fn copy
---
src/butil/containers/doubly_buffered_data.h | 138 +++++++---------------------
src/butil/type_traits.h | 6 +-
test/brpc_load_balancer_unittest.cpp | 25 ++++-
3 files changed, 60 insertions(+), 109 deletions(-)
diff --git a/src/butil/containers/doubly_buffered_data.h
b/src/butil/containers/doubly_buffered_data.h
index 62f67ead..5c97038b 100644
--- a/src/butil/containers/doubly_buffered_data.h
+++ b/src/butil/containers/doubly_buffered_data.h
@@ -123,83 +123,26 @@ public:
// Returns 0 on success, -1 otherwise.
int Read(ScopedPtr* ptr);
+ // `fn(const T&)' will be called with foreground instance.
+ // This function is not blocked by Read() and Modify() in other threads.
+ // Returns 0 on success, otherwise on error.
+ template<typename Fn>
+ int Read(Fn&& fn);
+
// Modify background and foreground instances. fn(T&, ...) will be called
// twice. Modify() from different threads are exclusive from each other.
// NOTE: Call same series of fn to different equivalent instances should
// result in equivalent instances, otherwise foreground and background
// instance will be inconsistent.
- template <typename Fn> size_t Modify(Fn& fn);
- template <typename Fn, typename Arg1> size_t Modify(Fn& fn, const Arg1&);
- template <typename Fn, typename Arg1, typename Arg2>
- size_t Modify(Fn& fn, const Arg1&, const Arg2&);
+ template <typename Fn, typename... Args>
+ size_t Modify(Fn&& fn, Args&&... args);
// fn(T& background, const T& foreground, ...) will be called to background
// and foreground instances respectively.
- template <typename Fn> size_t ModifyWithForeground(Fn& fn);
- template <typename Fn, typename Arg1>
- size_t ModifyWithForeground(Fn& fn, const Arg1&);
- template <typename Fn, typename Arg1, typename Arg2>
- size_t ModifyWithForeground(Fn& fn, const Arg1&, const Arg2&);
+ template <typename Fn, typename... Args>
+ size_t ModifyWithForeground(Fn&& fn, Args&&... args);
private:
- template <typename Fn>
- struct WithFG0 {
- WithFG0(Fn& fn, T* data) : _fn(fn), _data(data) { }
- size_t operator()(T& bg) {
- return _fn(bg, (const T&)_data[&bg == _data]);
- }
- private:
- Fn& _fn;
- T* _data;
- };
-
- template <typename Fn, typename Arg1>
- struct WithFG1 {
- WithFG1(Fn& fn, T* data, const Arg1& arg1)
- : _fn(fn), _data(data), _arg1(arg1) {}
- size_t operator()(T& bg) {
- return _fn(bg, (const T&)_data[&bg == _data], _arg1);
- }
- private:
- Fn& _fn;
- T* _data;
- const Arg1& _arg1;
- };
-
- template <typename Fn, typename Arg1, typename Arg2>
- struct WithFG2 {
- WithFG2(Fn& fn, T* data, const Arg1& arg1, const Arg2& arg2)
- : _fn(fn), _data(data), _arg1(arg1), _arg2(arg2) {}
- size_t operator()(T& bg) {
- return _fn(bg, (const T&)_data[&bg == _data], _arg1, _arg2);
- }
- private:
- Fn& _fn;
- T* _data;
- const Arg1& _arg1;
- const Arg2& _arg2;
- };
-
- template <typename Fn, typename Arg1>
- struct Closure1 {
- Closure1(Fn& fn, const Arg1& arg1) : _fn(fn), _arg1(arg1) {}
- size_t operator()(T& bg) { return _fn(bg, _arg1); }
- private:
- Fn& _fn;
- const Arg1& _arg1;
- };
-
- template <typename Fn, typename Arg1, typename Arg2>
- struct Closure2 {
- Closure2(Fn& fn, const Arg1& arg1, const Arg2& arg2)
- : _fn(fn), _arg1(arg1), _arg2(arg2) {}
- size_t operator()(T& bg) { return _fn(bg, _arg1, _arg2); }
- private:
- Fn& _fn;
- const Arg1& _arg1;
- const Arg2& _arg2;
- };
-
const T* UnsafeRead() const {
return _data + _index.load(butil::memory_order_acquire);
}
@@ -253,7 +196,8 @@ template <typename T, typename TLS, bool
AllowBthreadSuspended>
class DoublyBufferedData<T, TLS, AllowBthreadSuspended>::WrapperTLSGroup {
public:
const static size_t RAW_BLOCK_SIZE = 4096;
- const static size_t ELEMENTS_PER_BLOCK = RAW_BLOCK_SIZE / sizeof(Wrapper)
> 0 ? RAW_BLOCK_SIZE / sizeof(Wrapper) : 1;
+ const static size_t ELEMENTS_PER_BLOCK =
+ RAW_BLOCK_SIZE / sizeof(Wrapper) > 0 ? RAW_BLOCK_SIZE /
sizeof(Wrapper) : 1;
struct BAIDU_CACHELINE_ALIGNMENT ThreadBlock {
inline DoublyBufferedData::Wrapper* at(size_t offset) {
@@ -572,7 +516,20 @@ int DoublyBufferedData<T, TLS,
AllowBthreadSuspended>::Read(
template <typename T, typename TLS, bool AllowBthreadSuspended>
template <typename Fn>
-size_t DoublyBufferedData<T, TLS, AllowBthreadSuspended>::Modify(Fn& fn) {
+int DoublyBufferedData<T, TLS, AllowBthreadSuspended>::Read(Fn&& fn) {
+ BAIDU_CASSERT((is_result_void<Fn, const T&>::value),
+ "Fn must accept `const T&' and return void");
+ ScopedPtr ptr;
+ if (Read(&ptr) != 0) {
+ return -1;
+ }
+ fn(*ptr);
+ return 0;
+}
+
+template <typename T, typename TLS, bool AllowBthreadSuspended>
+template <typename Fn, typename... Args>
+size_t DoublyBufferedData<T, TLS, AllowBthreadSuspended>::Modify(Fn&& fn,
Args&&... args) {
// _modify_mutex sequences modifications. Using a separate mutex rather
// than _wrappers_mutex is to avoid blocking threads calling
// AddWrapper() or RemoveWrapper() too long. Most of the time,
modifications
@@ -581,7 +538,7 @@ size_t DoublyBufferedData<T, TLS,
AllowBthreadSuspended>::Modify(Fn& fn) {
int bg_index = !_index.load(butil::memory_order_relaxed);
// background instance is not accessed by other threads, being safe to
// modify.
- const size_t ret = fn(_data[bg_index]);
+ const size_t ret = fn(_data[bg_index], std::forward<Args>(args)...);
if (!ret) {
return 0;
}
@@ -607,46 +564,17 @@ size_t DoublyBufferedData<T, TLS,
AllowBthreadSuspended>::Modify(Fn& fn) {
}
}
- const size_t ret2 = fn(_data[bg_index]);
+ const size_t ret2 = fn(_data[bg_index], std::forward<Args>(args)...);
CHECK_EQ(ret2, ret) << "index=" <<
_index.load(butil::memory_order_relaxed);
return ret2;
}
template <typename T, typename TLS, bool AllowBthreadSuspended>
-template <typename Fn, typename Arg1>
-size_t DoublyBufferedData<T, TLS, AllowBthreadSuspended>::Modify(Fn& fn, const
Arg1& arg1) {
- Closure1<Fn, Arg1> c(fn, arg1);
- return Modify(c);
-}
-
-template <typename T, typename TLS, bool AllowBthreadSuspended>
-template <typename Fn, typename Arg1, typename Arg2>
-size_t DoublyBufferedData<T, TLS, AllowBthreadSuspended>::Modify(
- Fn& fn, const Arg1& arg1, const Arg2& arg2) {
- Closure2<Fn, Arg1, Arg2> c(fn, arg1, arg2);
- return Modify(c);
-}
-
-template <typename T, typename TLS, bool AllowBthreadSuspended>
-template <typename Fn>
-size_t DoublyBufferedData<T, TLS,
AllowBthreadSuspended>::ModifyWithForeground(Fn& fn) {
- WithFG0<Fn> c(fn, _data);
- return Modify(c);
-}
-
-template <typename T, typename TLS, bool AllowBthreadSuspended>
-template <typename Fn, typename Arg1>
-size_t DoublyBufferedData<T, TLS,
AllowBthreadSuspended>::ModifyWithForeground(Fn& fn, const Arg1& arg1) {
- WithFG1<Fn, Arg1> c(fn, _data, arg1);
- return Modify(c);
-}
-
-template <typename T, typename TLS, bool AllowBthreadSuspended>
-template <typename Fn, typename Arg1, typename Arg2>
-size_t DoublyBufferedData<T, TLS, AllowBthreadSuspended>::ModifyWithForeground(
- Fn& fn, const Arg1& arg1, const Arg2& arg2) {
- WithFG2<Fn, Arg1, Arg2> c(fn, _data, arg1, arg2);
- return Modify(c);
+template <typename Fn, typename... Args>
+size_t DoublyBufferedData<T, TLS,
AllowBthreadSuspended>::ModifyWithForeground(Fn&& fn, Args&&... args) {
+ return Modify([this, &fn](T& bg, Args&&... args) {
+ return fn(bg, (const T&)_data[&bg == _data],
std::forward<Args>(args)...);
+ }, std::forward<Args>(args)...);
}
} // namespace butil
diff --git a/src/butil/type_traits.h b/src/butil/type_traits.h
index 0ae91135..735e1e55 100644
--- a/src/butil/type_traits.h
+++ b/src/butil/type_traits.h
@@ -99,7 +99,7 @@ template <class T> struct is_pod
std::is_trivial<T>::value)> {};
#else
template <class T> struct is_pod : std::is_pod<T> {};
-#endif
+#endif // __cplusplus
#else
// We can't get is_pod right without compiler help, so fail conservatively.
@@ -334,7 +334,7 @@ template<typename T>
struct remove_cvref {
typedef typename remove_cv<typename remove_reference<T>::type>::type type;
};
-#endif
+#endif // __cplusplus
// is_reference is false except for reference types.
template<typename T> struct is_reference : false_type {};
@@ -378,7 +378,7 @@ template <typename F>
using result_of = std::result_of<F>;
#else
#error Only C++11 or later is supported.
-#endif
+#endif // __cplusplus
template <typename F>
using result_of_t = typename result_of<F>::type;
diff --git a/test/brpc_load_balancer_unittest.cpp
b/test/brpc_load_balancer_unittest.cpp
index 509456e7..2abb869e 100644
--- a/test/brpc_load_balancer_unittest.cpp
+++ b/test/brpc_load_balancer_unittest.cpp
@@ -80,6 +80,16 @@ bool AddN(Foo& f, int n) {
return true;
}
+void read_cb(const Foo& f) {
+ ASSERT_EQ(0, f.x);
+}
+
+struct CallableObj {
+ void operator()(const Foo& f) {
+ ASSERT_EQ(0, f.x);
+ }
+};
+
template <typename DBD>
void test_doubly_buffered_data() {
// test doubly_buffered_data TLS limits
@@ -97,6 +107,15 @@ void test_doubly_buffered_data() {
ASSERT_EQ(0, d.Read(&ptr));
ASSERT_EQ(0, ptr->x);
}
+ {
+ ASSERT_EQ(0, d.Read([](const Foo& f) {
+ ASSERT_EQ(0, f.x);
+ }));
+ ASSERT_EQ(0, d.Read(read_cb));
+ ASSERT_EQ(0, d.Read(CallableObj()));
+ CallableObj co;
+ ASSERT_EQ(0, d.Read(co));
+ }
{
typename DBD::ScopedPtr ptr;
ASSERT_EQ(0, d.Read(&ptr));
@@ -104,10 +123,14 @@ void test_doubly_buffered_data() {
}
d.Modify(AddN, 10);
+ d.Modify([](Foo& f, int n) -> size_t {
+ f.x += n;
+ return 1;
+ }, 10);
{
typename DBD::ScopedPtr ptr;
ASSERT_EQ(0, d.Read(&ptr));
- ASSERT_EQ(10, ptr->x);
+ ASSERT_EQ(20, ptr->x);
}
}
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