bugfix for chase lev

diff --git a/chase-lev-deque-bugfix/Makefile b/chase-lev-deque-bugfix/Makefile
new file mode 100644 (file)
index 0000000..91ff999
--- /dev/null
+++ b/chase-lev-deque-bugfix/Makefile
@@ -0,0 +1,17 @@
+include ../benchmarks.mk
+
+TESTNAME = main
+
+HEADERS = deque.h
+OBJECTS = main.o deque.o
+
+all: $(TESTNAME)
+
+$(TESTNAME): $(HEADERS) $(OBJECTS)
+       $(CC) -o $@ $(OBJECTS) $(CPPFLAGS) $(LDFLAGS)
+
+%.o: %.c
+       $(CC) -c -o $@ $< $(CPPFLAGS)
+
+clean:
+       rm -f $(TESTNAME) *.o

diff --git a/chase-lev-deque-bugfix/deque.c b/chase-lev-deque-bugfix/deque.c
new file mode 100644 (file)
index 0000000..6328446
--- /dev/null
+++ b/chase-lev-deque-bugfix/deque.c
@@ -0,0 +1,85 @@
+#include <stdatomic.h>
+#include <inttypes.h>
+#include "deque.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+Deque * create() {
+       Deque * q = (Deque *) calloc(1, sizeof(Deque));
+       Array * a = (Array *) calloc(1, sizeof(Array)+2*sizeof(atomic_int));
+       atomic_store_explicit(&q->array, a, memory_order_relaxed);
+       atomic_store_explicit(&q->top, 0, memory_order_relaxed);
+       atomic_store_explicit(&q->bottom, 0, memory_order_relaxed);
+       atomic_store_explicit(&a->size, 2, memory_order_relaxed);
+       return q;
+}
+
+int take(Deque *q) {
+       size_t b = atomic_load_explicit(&q->bottom, memory_order_relaxed) - 1;
+       Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
+       atomic_store_explicit(&q->bottom, b, memory_order_relaxed);
+       atomic_thread_fence(memory_order_seq_cst);
+       size_t t = atomic_load_explicit(&q->top, memory_order_relaxed);
+       int x;
+       if (t <= b) {
+               /* Non-empty queue. */
+               x = atomic_load_explicit(&a->buffer[b % atomic_load_explicit(&a->size,memory_order_relaxed)], memory_order_relaxed);
+               if (t == b) {
+                       /* Single last element in queue. */
+                       if (!atomic_compare_exchange_strong_explicit(&q->top, &t, t + 1, memory_order_seq_cst, memory_order_relaxed))
+                               /* Failed race. */
+                               x = EMPTY;
+                       atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
+               }
+       } else { /* Empty queue. */
+               x = EMPTY;
+               atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
+       }
+       return x;
+}
+
+void resize(Deque *q) {
+       Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
+       size_t size=atomic_load_explicit(&a->size, memory_order_relaxed);
+       size_t new_size=size << 1;
+       Array *new_a = (Array *) calloc(1, new_size * sizeof(atomic_int) + sizeof(Array));
+       size_t top=atomic_load_explicit(&q->top, memory_order_relaxed);
+       size_t bottom=atomic_load_explicit(&q->bottom, memory_order_relaxed);
+       atomic_store_explicit(&new_a->size, new_size, memory_order_relaxed);
+       size_t i;
+       for(i=top; i < bottom; i++) {
+               atomic_store_explicit(&new_a->buffer[i % new_size], atomic_load_explicit(&a->buffer[i % size], memory_order_relaxed), memory_order_relaxed);
+       }
+       atomic_store_explicit(&q->array, new_a, memory_order_release);
+       printf("resize\n");
+}
+
+void push(Deque *q, int x) {
+       size_t b = atomic_load_explicit(&q->bottom, memory_order_relaxed);
+       size_t t = atomic_load_explicit(&q->top, memory_order_acquire);
+       Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
+       if (b - t > atomic_load_explicit(&a->size, memory_order_relaxed) - 1) /* Full queue. */ {
+               resize(q);
+               //Bug in paper...should have next line...
+               a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
+       }
+       atomic_store_explicit(&a->buffer[b % atomic_load_explicit(&a->size, memory_order_relaxed)], x, memory_order_relaxed);
+       atomic_thread_fence(memory_order_release);
+       atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
+}
+
+int steal(Deque *q) {
+       size_t t = atomic_load_explicit(&q->top, memory_order_acquire);
+       atomic_thread_fence(memory_order_seq_cst);
+       size_t b = atomic_load_explicit(&q->bottom, memory_order_acquire);
+       int x = EMPTY;
+       if (t < b) {
+               /* Non-empty queue. */
+               Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_acquire);
+               x = atomic_load_explicit(&a->buffer[t % atomic_load_explicit(&a->size, memory_order_relaxed)], memory_order_relaxed);
+               if (!atomic_compare_exchange_strong_explicit(&q->top, &t, t + 1, memory_order_seq_cst, memory_order_relaxed))
+                       /* Failed race. */
+                       return ABORT;
+       }
+       return x;
+}

diff --git a/chase-lev-deque-bugfix/deque.h b/chase-lev-deque-bugfix/deque.h
new file mode 100644 (file)
index 0000000..bc670e7
--- /dev/null
+++ b/chase-lev-deque-bugfix/deque.h
@@ -0,0 +1,22 @@
+#ifndef DEQUE_H
+#define DEQUE_H
+
+typedef struct {
+       atomic_size_t size;
+       atomic_int buffer[];
+} Array;
+
+typedef struct {
+       atomic_size_t top, bottom;
+       atomic_uintptr_t array; /* Atomic(Array *) */
+} Deque;
+
+Deque * create();
+int take(Deque *q);
+void resize(Deque *q);
+void push(Deque *q, int x);
+
+#define EMPTY 0xffffffff
+#define ABORT 0xfffffffe
+
+#endif

diff --git a/chase-lev-deque-bugfix/main.c b/chase-lev-deque-bugfix/main.c
new file mode 100644 (file)
index 0000000..f2e8dca
--- /dev/null
+++ b/chase-lev-deque-bugfix/main.c
@@ -0,0 +1,46 @@
+#include <stdlib.h>
+#include <assert.h>
+#include <stdio.h>
+#include <threads.h>
+#include <stdatomic.h>
+
+#include "model-assert.h"
+
+#include "deque.h"
+
+Deque *q;
+int a;
+int b;
+int c;
+
+static void task(void * param) {
+       a=steal(q);
+}
+
+int user_main(int argc, char **argv)
+{
+       thrd_t t;
+       q=create();
+       thrd_create(&t, task, 0);
+       push(q, 1);
+       push(q, 2);
+       push(q, 4);
+       b=take(q);
+       c=take(q);
+       thrd_join(t);
+
+       bool correct=true;
+       if (a!=1 && a!=2 && a!=4 && a!= EMPTY)
+               correct=false;
+       if (b!=1 && b!=2 && b!=4 && b!= EMPTY)
+               correct=false;
+       if (c!=1 && c!=2 && c!=4 && a!= EMPTY)
+               correct=false;
+       if (a!=EMPTY && b!=EMPTY && c!=EMPTY && (a+b+c)!=7)
+               correct=false;
+       if (!correct)
+               printf("a=%d b=%d c=%d\n",a,b,c);
+       MODEL_ASSERT(correct);
+
+       return 0;
+}