From f066e8d59f41a0f5f4d60908bc53608a8250978b Mon Sep 17 00:00:00 2001
From: Berenger Bramas <Berenger.Bramas@inria.fr>
Date: Wed, 19 May 2021 14:37:51 +0200
Subject: [PATCH] Second bug solved (update the lock free bool array)
---
cpp/particles/lock_free_bool_array.hpp | 54 ++++++++++++++++++++------
1 file changed, 42 insertions(+), 12 deletions(-)
diff --git a/cpp/particles/lock_free_bool_array.hpp b/cpp/particles/lock_free_bool_array.hpp
index 4e5ad31b..ae5eb0d4 100644
--- a/cpp/particles/lock_free_bool_array.hpp
+++ b/cpp/particles/lock_free_bool_array.hpp
@@ -27,31 +27,61 @@
#define LOCK_FREE_BOOL_ARRAY_HPP
#include <vector>
-#include <memory>
+#include <atomic>
+#include <unistd.h>
+#include <cstdio>
+#include <omp.h>
+
class lock_free_bool_array{
- std::vector<std::unique_ptr<long int>> keys;
+ static const int Available = 0;
+ static const int Busy = 1;
+ static const int NoOwner = -1;
+
+ struct Locker {
+ Locker() : lock(Available), ownerId(NoOwner), counter(0) {}
+ std::atomic_int lock;
+ std::atomic_int ownerId;
+ int counter;
+ };
+
+ std::vector<std::unique_ptr<Locker>> keys;
+
public:
- explicit lock_free_bool_array(const long int inNbKeys = 512){
+ explicit lock_free_bool_array(const long int inNbKeys = 1024){
keys.resize(inNbKeys);
- for(std::unique_ptr<long int>& k : keys){
- k.reset(new long int(0));
+ for(auto& k : keys){
+ k.reset(new Locker());
}
}
void lock(const long int inKey){
- volatile long int* k = keys[inKey%keys.size()].get();
- long int res = 1;
- while(res == 1){
- res = __sync_val_compare_and_swap(k, 0, res);
+ Locker* k = keys[inKey%keys.size()].get();
+ if(k->ownerId.load() != omp_get_thread_num()){
+ int expected = Available;
+ while(!std::atomic_compare_exchange_strong(&k->lock, &expected, Busy)){
+ usleep(1);
+ }
+ k->ownerId.store(omp_get_thread_num());
+ k->counter = 0; // must remain
}
+ k->counter += 1;
+ assert(k->lock.load() == Busy);
+ assert(k->counter >= 1);
+ assert(k->ownerId.load() == omp_get_thread_num());
}
void unlock(const long int inKey){
- volatile long int* k = keys[inKey%keys.size()].get();
- assert(k && *k);
- (*k) = 0;
+ Locker* k = keys[inKey%keys.size()].get();
+ assert(k->lock.load() == Busy);
+ assert(k->counter >= 1);
+ assert(k->ownerId.load() == omp_get_thread_num());
+ k->counter -= 1;
+ if(k->counter == 0){
+ k->ownerId.store(NoOwner);
+ k->lock.store(Available);
+ }
}
};
--
GitLab