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fix(util/rc): reference counter memory_order flags

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See discussion at
http://www.chaoticmind.net/~hcb/projects/boost.atomic/doc/atomic/usage_examples.html#boost_atomic.usage_examples.example_reference_counters
http://stackoverflow.com/questions/10268737/c11-atomics-and-intrusive-shared-pointer-reference-count

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit is contained in:
Leonardo de Moura 2014-07-21 08:22:58 -07:00
parent c0f862d88a
commit de657e8df0
3 changed files with 23 additions and 4 deletions
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6
src/library/module.cpp
View file

@ -336,13 +336,15 @@ struct import_modules_fn {
}
obj_counter++;
}
if (atomic_fetch_sub_explicit(&m_import_counter, 1u, memory_order_relaxed) == 1u) {
if (atomic_fetch_sub_explicit(&m_import_counter, 1u, memory_order_release) == 1u) {
atomic_thread_fence(memory_order_acquire);
m_all_modules_imported = true;
m_asynch_cv.notify_all();
}
// Module was successfully imported, we should notify descendents.
for (module_info_ptr const & d : r->m_dependents) {
if (atomic_fetch_sub_explicit(&(d->m_counter), 1u, memory_order_relaxed) == 1u) {
if (atomic_fetch_sub_explicit(&(d->m_counter), 1u, memory_order_release) == 1u) {
atomic_thread_fence(memory_order_acquire);
// all d's dependencies have been processed
add_import_module_task(d);
}

12
src/util/rc.h
View file

@ -16,8 +16,16 @@ atomic<unsigned> m_rc; \
public: \
unsigned get_rc() const { return atomic_load(&m_rc); } \
void inc_ref() { atomic_fetch_add_explicit(&m_rc, 1u, memory_order_relaxed); } \
bool dec_ref_core() { lean_assert(get_rc() > 0); return atomic_fetch_sub_explicit(&m_rc, 1u, memory_order_relaxed) == 1u; } \
void dec_ref() { if (dec_ref_core()) dealloc(); }
bool dec_ref_core() { \
lean_assert(get_rc() > 0); \
if (atomic_fetch_sub_explicit(&m_rc, 1u, memory_order_release) == 1u) { \
atomic_thread_fence(memory_order_acquire); \
return true; \
} else { \
return false; \
} \
} \
void dec_ref() { if (dec_ref_core()) { dealloc(); } }
#define LEAN_COPY_REF(Arg) \
if (Arg.m_ptr) \

9
src/util/thread.h
View file

@ -31,6 +31,9 @@ using std::atomic_load;
using std::atomic_fetch_add_explicit;
using std::atomic_fetch_sub_explicit;
using std::memory_order_relaxed;
using std::memory_order_release;
using std::memory_order_acquire;
using std::atomic_thread_fence;
namespace chrono = std::chrono;
namespace this_thread = std::this_thread;
}
@ -46,9 +49,12 @@ using boost::mutex;
using boost::recursive_mutex;
using boost::atomic;
using boost::memory_order_relaxed;
using boost::memory_order_acquire;
using boost::memory_order_release;
using boost::condition_variable;
using boost::unique_lock;
using boost::lock_guard;
using boost::atomic_thread_fence;
namespace chrono = boost::chrono;
namespace this_thread = boost::this_thread;
typedef atomic<bool> atomic_bool;
@ -71,6 +77,9 @@ namespace chrono {
typedef unsigned milliseconds;
}
constexpr int memory_order_relaxed = 0;
constexpr int memory_order_release = 0;
constexpr int memory_order_acquire = 0;
inline void atomic_thread_fence(int ) {}
template<typename T>
class atomic {
T m_value;