bst_lock_kung.c

/******************************************************************************
 * bst_lock_kung.c
 *
 * Lock-based binary search trees (BSTs), based on:
 *  H. T. Kung and Philip L. Lehman.
 *  "Concurrent manipulation of binary search trees".
 *  ACM Tranactions on Database Systems, Vol. 5, No. 3, September 1980.
 *
 * Copyright (c) 2002-2003, K A Fraser

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

    * Redistributions of source code must retain the above copyright
    * notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above
    * copyright notice, this list of conditions and the following
    * disclaimer in the documentation and/or other materials provided
    * with the distribution.  Neither the name of the Keir Fraser
    * nor the names of its contributors may be used to endorse or
    * promote products derived from this software without specific
    * prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#define __SET_IMPLEMENTATION__

#include <ucontext.h>
#include <signal.h>
#include <stdio.h>
#include <limits.h>
#include <errno.h>
#include <stdlib.h>
#include <assert.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdarg.h>
#include "portable_defns.h"
#include "gc.h"
#include "set.h"

#define IS_BLUE(_n)      ((int)(_n)->v & 1)
#define MK_BLUE(_n)      ((_n)->v = (setval_t)((unsigned long)(_n)->v | 1))

#define GET_VALUE(_n) ((setval_t)((unsigned long)(_n)->v & ~1UL))

#define LEFT  0
#define RIGHT 1
#define FOLLOW(_n, _d) ((_d) ? (_n)->r : (_n)->l)
#define UPDATE(_n, _d, _x) ((_d) ? ((_n)->r = (_x)) : ((_n)->l = (_x)))
#define FLIP(_d) ((_d)^1)

typedef struct node_st node_t;
typedef struct set_st set_t;

struct node_st
{
    setkey_t k;
    setval_t v;
    node_t *l, *r, *p;
    mcs_lock_t lock;
};

struct set_st
{
    node_t root;
};

static int gc_id;

#define LOCK(_n, _pqn)   mcs_lock(&(_n)->lock, (_pqn))
#define UNLOCK(_n, _pqn) mcs_unlock(&(_n)->lock, (_pqn))


static node_t *weak_find(node_t *n, setkey_t k)
{
    while ( n != NULL )
    {
        if ( n->k < k )
            n = n->r;
        else if ( n->k > k )
            n = n->l;
        else
            break;
    }
    return n;
}


static node_t *find(node_t *n, setkey_t k, qnode_t *qn, int *pdir)
{
    int dir;
    node_t *f, *s;

    s = n;

    do {
        f = s;
    retry:
        if ( k < f->k )
        {
            dir = LEFT;
            s   = f->l;
        }
        else
        {
            dir = RIGHT;
            s   = f->r;
        }
    }
    while ( (s != NULL) && (s->k != k) );

    LOCK(f, qn);
    if ( IS_BLUE(f) )
    {
        UNLOCK(f, qn);
        f = f->p;
        goto retry;
    }
    if ( s != FOLLOW(f, dir) )
    {
        UNLOCK(f, qn);
        goto retry;
    }

    *pdir = dir;
    return f;
}


static node_t *rotate(ptst_t *ptst, node_t *a, int dir1,
                      int dir2, node_t **pc, qnode_t *pqn[])
{
    node_t *b = FOLLOW(a, dir1), *c = FOLLOW(b, dir2);
    node_t *bp = gc_alloc(ptst, gc_id), *cp = gc_alloc(ptst, gc_id);
    qnode_t c_qn;

    LOCK(c, &c_qn);

    memcpy(bp, b, sizeof(*b));
    memcpy(cp, c, sizeof(*c));

    mcs_init(&bp->lock);
    mcs_init(&cp->lock);

    LOCK(bp, pqn[3]);
    LOCK(cp, pqn[2]);

    assert(!IS_BLUE(a));
    assert(!IS_BLUE(b));
    assert(!IS_BLUE(c));

    UPDATE(cp, FLIP(dir2), bp);
    UPDATE(bp, dir2,       FOLLOW(c, FLIP(dir2)));

    UPDATE(a, dir1, cp);
    b->p = a;
    MK_BLUE(b);
    c->p = cp;
    MK_BLUE(c);

    gc_free(ptst, b, gc_id);
    gc_free(ptst, c, gc_id);

    UNLOCK(a, pqn[0]);
    UNLOCK(b, pqn[1]);
    UNLOCK(c, &c_qn);

    *pc = bp;
    return cp;
}


static void _remove(ptst_t *ptst, node_t *a, int dir1, int dir2, qnode_t **pqn)
{
    node_t *b = FOLLOW(a, dir1), *c = FOLLOW(b, dir2);
    assert(FOLLOW(b, FLIP(dir2)) == NULL);
    assert(!IS_BLUE(a));
    assert(!IS_BLUE(b));
    UPDATE(a, dir1,       c);
    UPDATE(b, FLIP(dir2), c);
    b->p = a;
    MK_BLUE(b);
    gc_free(ptst, b, gc_id);
    UNLOCK(a, pqn[0]);
    UNLOCK(b, pqn[1]);
}


static void delete_by_rotation(ptst_t *ptst, node_t *f, int dir,
                               qnode_t *pqn[], int lock_idx)
{
    node_t *g, *h, *s = FOLLOW(f, dir);

    if ( s->v != NULL )
    {
        UNLOCK(f, pqn[lock_idx+0]);
        UNLOCK(s, pqn[lock_idx+1]);
        return;
    }

    if ( s->l == NULL )
        _remove(ptst, f, dir, RIGHT, pqn+lock_idx);
    else if ( s->r == NULL )
        _remove(ptst, f, dir, LEFT, pqn+lock_idx);
    else
    {
        g = rotate(ptst, f, dir, LEFT, &h, pqn+lock_idx);
        lock_idx ^= 2;
        if ( h->l == NULL )
        {
            assert(h->v == NULL);
            _remove(ptst, g, RIGHT, RIGHT, pqn+lock_idx);
        }
        else
        {
            delete_by_rotation(ptst, g, RIGHT, pqn, lock_idx);
            LOCK(f, pqn[0]);
            if ( (g != FOLLOW(f, dir)) || IS_BLUE(f) )
            {
                UNLOCK(f, pqn[0]);
            }
            else
            {
                LOCK(g, pqn[1]);
                /*
                 * XXX Check that there is a node H to be rotated up.
                 * This is missing from the original paper, and must surely
                 * be a bug (we lost all locks at previous delete_by_rotation,
                 * so we can't know the existence of G's children).
                 */
                if ( g->r != NULL )
                {
                    g = rotate(ptst, f, dir, RIGHT, &h, pqn);
                    UNLOCK(g, pqn[2]);
                    UNLOCK(h, pqn[3]);
                }
                else
                {
                    UNLOCK(f, pqn[0]);
                    UNLOCK(g, pqn[1]);
                }
            }
        }
    }
}


set_t *set_alloc(void)
{
    set_t *s;

    s = malloc(sizeof(*s));
    mcs_init(&s->root.lock);
    s->root.k = SENTINEL_KEYMIN;
    s->root.v = (setval_t)(~1UL); /* dummy root node is white. */
    s->root.l = NULL;
    s->root.r = NULL;

    return s;
}


setval_t set_update(set_t *s, setkey_t k, setval_t v, int overwrite)
{
    node_t  *f, *w;
    qnode_t  f_qn, w_qn;
    int dir;
    setval_t ov = NULL;
    ptst_t  *ptst;

    k = CALLER_TO_INTERNAL_KEY(k);

    ptst = critical_enter();

 retry:
    f = find(&s->root, k, &f_qn, &dir);

    if ( (w = FOLLOW(f, dir)) != NULL )
    {
        /* Protected by parent lock. */
        assert(!IS_BLUE(w));
        ov = w->v;
        if ( overwrite || (ov == NULL) ) w->v = v;
    }
    else
    {
        w = gc_alloc(ptst, gc_id);
        w->l = NULL;
        w->r = NULL;
        w->v = v;
        w->k = k;
        mcs_init(&w->lock);
        UPDATE(f, dir, w);
    }

    UNLOCK(f, &f_qn);

    critical_exit(ptst);

    return ov;
}


setval_t set_remove(set_t *s, setkey_t k)
{
    node_t *f, *w;
    qnode_t qn[4], *pqn[] = { qn+0, qn+1, qn+2, qn+3, qn+0, qn+1 };
    int dir;
    setval_t v = NULL;
    ptst_t *ptst;

    k = CALLER_TO_INTERNAL_KEY(k);

    ptst = critical_enter();

    f = find(&s->root, k, pqn[0], &dir);
    if ( (w = FOLLOW(f, dir)) != NULL )
    {
        LOCK(w, pqn[1]);
        v = w->v;
        w->v = NULL;
        assert(!IS_BLUE(w));
        delete_by_rotation(ptst, f, dir, pqn, 0);
    }
    else
    {
        UNLOCK(f, pqn[0]);
    }

    critical_exit(ptst);

    return v;
}


setval_t set_lookup(set_t *s, setkey_t k)
{
    node_t *n;
    setval_t v = NULL;
    ptst_t *ptst;

    k = CALLER_TO_INTERNAL_KEY(k);

    ptst = critical_enter();

    n = weak_find(&s->root, k);
    if ( n != NULL ) v = GET_VALUE(n);

    critical_exit(ptst);
    return v;
}


void _init_set_subsystem(void)
{
    gc_id = gc_add_allocator(sizeof(node_t));
}