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lll.c
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lll.c
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//! \file textbook lock-free linked list, harris
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <stdatomic.h> // gcc -latomic
#include <assert.h>
#include "linkedlist.h"
//#define SC //! memory model
#define UNMARK_MASK ~1
#define MARK_BIT 0x0000000000001
#define getptr(_markedpointer) ((lln)(((J)_markedpointer)&UNMARK_MASK))
#define ismarked(_markedpointer) ((((J)_markedpointer)&MARK_BIT)!=0x0)
#define setmark(_markedpointer) ((lln)(((J)_markedpointer)|MARK_BIT))
#ifdef SC
#define CAS(_a,_e,_d) atomic_compare_exchange_weak(_a,_e,_d)
#define LOAD(_a) atomic_load(_a)
#define STORE(_a,_e) atomic_store(_a,_e)
#define FAO(_a,_e) atomic_fetch_or(_a,_e)
#else
#define CAS(_a,_e,_d) atomic_compare_exchange_weak_explicit(_a,_e,_d,memory_order_acq_rel,memory_order_acquire)
#define LOAD(_a) atomic_load_explicit(_a,memory_order_acquire)
#define STORE(_a,_e) atomic_store_explicit(_a,_e,memory_order_release)
#define FAO(_a,_e) atomic_fetch_or_explicit(_a,_e,memory_order_acq_rel)
#endif
_ llnew(lln head,lln tail,ll list){
list->head = head;
list->tail = tail;
//! sentinels
list->head->key = LONG_MIN;
list->head->next = tail;
list->tail->key = LONG_MAX;
list->tail->next = 0;
list->pred = head;
list->curr = 0;
list->free = 0;
#ifdef COUNTERS
list->adds = 0;
list->rems = 0;
list->cons = 0;
list->trav = 0;
list->fail = 0;
list->rtry = 0;
#endif
}
_ llzap(ll list){
lln next,node;
next=list->free;
W(next){
node=next;
next=next->free;
free(node);}
list->free=0;
}
_ llpos(J key, ll list){
lln pred,succ,curr,next;
retry:
pred=list->head;
curr=getptr(LOAD(&pred->next));
INC(list->trav);
assert(pred->key < key);
W(1){
succ=LOAD(&curr->next);
W(ismarked(succ)){
succ=getptr(succ);
if(!CAS(&pred->next,&curr,succ)){
INC(list->fail);
INC(list->rtry);
goto retry;
}
curr=getptr(succ);
succ=LOAD(&succ->next);
INC(list->trav);
}
if(key<=curr->key) {
assert(pred->key<curr->key);
list->pred=pred;
list->curr=curr;
R;}
pred = curr;
curr = getptr(LOAD(&curr->next));
INC(list->trav);
}
}
I lladd(J key, ll list) {
lln pred,curr,node;
node=new(LLN);
assert(node);
node->key = key;
W(1){
llpos(key, list);
pred=list->pred;
curr=list->curr;
P(curr->key==key,free(node),0) //!< already there
node->next = curr;
P(CAS(&pred->next,&curr,node),INC(list->adds),1)
INC(list->fail);}
}
I lldel(J key,ll list){
lln pred,succ,node,markedsucc;
W(1){
llpos(key,list);
pred=list->pred;
node=list->curr;
P(node->key!=key,0) //!< not there
succ=getptr(LOAD(&node->next)); //!< unmarked
markedsucc=setmark(succ);
if(!CAS(&node->next,&succ,markedsucc)){
INC(list->fail);
continue;}
if(!CAS(&pred->next,&node,succ))
node=list->curr; //!< beware!
node->free=list->free;
list->free=node;
R INC(list->rems),1;
}
}
I llcon(J key, ll list){
lln curr = list->head;
assert(curr->key <= key);
W(key>curr->key) {
curr=getptr(LOAD(&curr->next));
INC(list->cons);
}
R(curr->key==key&&!ismarked(LOAD(&curr->next)));
}
//:~