rb_lock_serialisedwriters.c

/******************************************************************************
 * rb_lock_serialisedwriters.c
 *
 * Lock-based red-black trees, using multi-reader locks.
 *
 * Updates are serialised on a global mutual-exclusion spinlock.
 *
 * Updates never need to read-lock, as updates are serialised. Must write-lock
 * for all node changes except colour changes and parent-link updates.
 *
 * Searches must read-lock down the tree, as they do not serialise.
 *
 * 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 <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include "portable_defns.h"
#include "gc.h"
#include "set.h"

#define IS_BLACK(_v)   ((int_addr_t)(_v)&1)
#define IS_RED(_v)     (!IS_BLACK(_v))
#define MK_BLACK(_v)   ((setval_t)((int_addr_t)(_v)|1))
#define MK_RED(_v)     ((setval_t)((int_addr_t)(_v)&~1))
#define GET_VALUE(_v)  (MK_RED(_v))
#define GET_COLOUR(_v) (IS_BLACK(_v))
#define SET_COLOUR(_v,_c) ((setval_t)((unsigned long)(_v)|(unsigned long)(_c)))

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;
    mrsw_lock_t lock;
};

struct set_st
{
    node_t root;
    CACHE_PAD(0);
    mcs_lock_t writer_lock;
};

static node_t null;
static int gc_id;

static void left_rotate(node_t *x)
{
    mrsw_qnode_t p_qn, x_qn, y_qn;
    node_t *y = x->r, *p = x->p;

    wr_lock(&p->lock, &p_qn);
    wr_lock(&x->lock, &x_qn);
    wr_lock(&y->lock, &y_qn);

    /* No need to write-lock to update parent link. */
    if ( (x->r = y->l) != &null ) x->r->p = x;

    x->p = y;
    y->l = x;
    y->p = p;
    if ( x == p->l ) p->l = y; else p->r = y;

    wr_unlock(&y->lock, &y_qn);
    wr_unlock(&x->lock, &x_qn);
    wr_unlock(&p->lock, &p_qn);
}


static void right_rotate(node_t *x)
{
    mrsw_qnode_t p_qn, x_qn, y_qn;
    node_t *y = x->l, *p = x->p;

    wr_lock(&p->lock, &p_qn);
    wr_lock(&x->lock, &x_qn);
    wr_lock(&y->lock, &y_qn);

    /* No need to write-lock to update parent link. */
    if ( (x->l = y->r) != &null ) x->l->p = x;

    x->p = y;
    y->r = x;
    y->p = p;
    if ( x == p->l ) p->l = y; else p->r = y;

    wr_unlock(&y->lock, &y_qn);
    wr_unlock(&x->lock, &x_qn);
    wr_unlock(&p->lock, &p_qn);
}


/* No locks held on entry/exit. Colour changes safe. Rotations lock for us. */
static void delete_fixup(ptst_t *ptst, set_t *s, node_t *x)
{
    node_t *p, *w;

    while ( (x->p != &s->root) && IS_BLACK(x->v) )
    {
        p = x->p;

        if ( x == p->l )
        {
            w = p->r;
            if ( IS_RED(w->v) )
            {
                w->v = MK_BLACK(w->v);
                p->v = MK_RED(p->v);
                /* Node W will be new parent of P. */
                left_rotate(p);
                /* Get new sibling W. */
                w = p->r;
            }

            if ( IS_BLACK(w->l->v) && IS_BLACK(w->r->v) )
            {
                w->v = MK_RED(w->v);
                x = p;
            }
            else
            {
                if ( IS_BLACK(w->r->v) )
                {
                    /* w->l is red => it cannot be null node. */
                    w->l->v = MK_BLACK(w->l->v);
                    w->v  = MK_RED(w->v);
                    right_rotate(w);
                    /* Old w is new w->r. Old w->l is new w.*/
                    w = p->r;
                }

                w->v = SET_COLOUR(GET_VALUE(w->v), GET_COLOUR(p->v));
                p->v = MK_BLACK(p->v);
                w->r->v = MK_BLACK(w->r->v);
                left_rotate(p);
                break;
            }
        }
        else /* SYMMETRIC CASE */
        {
            w = p->l;
            if ( IS_RED(w->v) )
            {
                w->v = MK_BLACK(w->v);
                p->v = MK_RED(p->v);
                /* Node W will be new parent of P. */
                right_rotate(p);
                /* Get new sibling W. */
                w = p->l;
            }

            if ( IS_BLACK(w->l->v) && IS_BLACK(w->r->v) )
            {
                w->v = MK_RED(w->v);
                x = p;
            }
            else
            {
                if ( IS_BLACK(w->l->v) )
                {
                    /* w->r is red => it cannot be the null node. */
                    w->r->v = MK_BLACK(w->r->v);
                    w->v  = MK_RED(w->v);
                    left_rotate(w);
                    /* Old w is new w->l. Old w->r is new w.*/
                    w = p->l;
                }

                w->v = SET_COLOUR(GET_VALUE(w->v), GET_COLOUR(p->v));
                p->v = MK_BLACK(p->v);
                w->l->v = MK_BLACK(w->l->v);
                right_rotate(p);
                break;
            }
        }
    }

    x->v = MK_BLACK(x->v);
}


set_t *set_alloc(void)
{
    ptst_t *ptst;
    set_t  *set;
    node_t *root;

    ptst = critical_enter();

    set = (set_t *)malloc(sizeof(*set));

    root = &set->root;
    root->k = SENTINEL_KEYMIN;
    root->v = MK_RED(NULL);
    root->l = &null;
    root->r = &null;
    root->p = NULL;
    mrsw_init(&root->lock);

    mcs_init(&set->writer_lock);

    critical_exit(ptst);

    return set;
}


setval_t set_update(set_t *s, setkey_t k, setval_t v, int overwrite)
{
    ptst_t  *ptst;
    node_t  *x, *p, *g, *y, *new;
    mrsw_qnode_t x_qn;
    qnode_t writer_qn;
    setval_t ov;

    k = CALLER_TO_INTERNAL_KEY(k);

    ptst = critical_enter();

    mcs_lock(&s->writer_lock, &writer_qn);

    x = &s->root;
    while ( (y = (k < x->k) ? x->l : x->r) != &null )
    {
        x = y;
        if ( k == x->k ) break;
    }

    if ( k == x->k )
    {
        ov = x->v;
        /* Lock X to change mapping. */
        wr_lock(&x->lock, &x_qn);
        if ( overwrite ) x->v = SET_COLOUR(v, GET_COLOUR(ov));
        wr_unlock(&x->lock, &x_qn);
        ov = GET_VALUE(ov);
    }
    else
    {
        ov = NULL;

        new = (node_t *)gc_alloc(ptst, gc_id);
        new->k = k;
        new->v = MK_RED(v);
        new->l = &null;
        new->r = &null;
        new->p = x;
        mrsw_init(&new->lock);

        /* Lock X to change a child. */
        wr_lock(&x->lock, &x_qn);
        if ( k < x->k ) x->l = new; else x->r = new;
        wr_unlock(&x->lock, &x_qn);

        x = new;

        /* No locks held here. Colour changes safe. Rotations lock for us. */
        for ( ; ; )
        {
            if ( (p = x->p) == &s->root )
            {
                x->v = MK_BLACK(x->v);
                break;
            }

            if ( IS_BLACK(p->v) ) break;

            g = p->p;
            if ( p == g->l )
            {
                y = g->r;
                if ( IS_RED(y->v) )
                {
                    p->v = MK_BLACK(p->v);
                    y->v = MK_BLACK(y->v);
                    g->v = MK_RED(g->v);
                    x = g;
                }
                else
                {
                    if ( x == p->r )
                    {
                        x = p;
                        left_rotate(x);
                        /* X and P switched round. */
                        p = x->p;
                    }
                    p->v = MK_BLACK(p->v);
                    g->v = MK_RED(g->v);
                    right_rotate(g);
                    /* G no longer on the path. */
                }
            }
            else /* SYMMETRIC CASE */
            {
                y = g->l;
                if ( IS_RED(y->v) )
                {
                    p->v = MK_BLACK(p->v);
                    y->v = MK_BLACK(y->v);
                    g->v = MK_RED(g->v);
                    x = g;
                }
                else
                {
                    if ( x == p->l )
                    {
                        x = p;
                        right_rotate(x);
                        /* X and P switched round. */
                        p = x->p;
                    }
                    p->v = MK_BLACK(p->v);
                    g->v = MK_RED(g->v);
                    left_rotate(g);
                    /* G no longer on the path. */
                }
            }
        }
    }

    mcs_unlock(&s->writer_lock, &writer_qn);

    critical_exit(ptst);

    return ov;
}


setval_t set_remove(set_t *s, setkey_t k)
{
    ptst_t  *ptst;
    node_t  *x, *y, *z;
    mrsw_qnode_t qn[2], *y_pqn=qn+0, *yp_pqn=qn+1, *t_pqn;
    mrsw_qnode_t z_qn, zp_qn;
    qnode_t writer_qn;
    setval_t ov = NULL;

    k = CALLER_TO_INTERNAL_KEY(k);

    ptst = critical_enter();

    mcs_lock(&s->writer_lock, &writer_qn);

    z = &s->root;
    while ( (z = (k < z->k) ? z->l : z->r) != &null )
    {
        if ( k == z->k ) break;
    }

    if ( k == z->k )
    {
        ov = GET_VALUE(z->v);

        if ( (z->l != &null) && (z->r != &null) )
        {
            /* Lock Z. It will get new key copied in. */
            wr_lock(&z->lock, &z_qn);
            y = z->r;
            /*
             * Write-lock from Z to Y. We end up with (YP,Y) locked.
             * Write-coupling is needed so we don't overtake searches for Y.
             */
            wr_lock(&y->lock, y_pqn);
            while ( y->l != &null )
            {
                if ( y->p != z ) wr_unlock(&y->p->lock, yp_pqn);
                y = y->l;
                t_pqn  = yp_pqn;
                yp_pqn = y_pqn;
                y_pqn  = t_pqn;
                wr_lock(&y->lock, y_pqn);
            }
        }
        else
        {
            y = z;
            /* Lock ZP. It will get new child. */
            wr_lock(&z->p->lock, &zp_qn);
            /* Lock Z. It will be deleted. */
            wr_lock(&z->lock, &z_qn);
        }

        /* No need to lock X. Only parent link is modified. */
        x = (y->l != &null) ? y->l : y->r;
        x->p = y->p;

        if ( y == y->p->l ) y->p->l = x; else y->p->r = x;

        if ( y != z )
        {
            z->k = y->k;
            z->v = SET_COLOUR(GET_VALUE(y->v), GET_COLOUR(z->v));
            if ( y->p != z ) wr_unlock(&y->p->lock, yp_pqn);
            wr_unlock(&y->lock, y_pqn);
        }
        else
        {
            wr_unlock(&z->p->lock, &zp_qn);
        }

        wr_unlock(&z->lock, &z_qn);

        gc_free(ptst, y, gc_id);

        if ( IS_BLACK(y->v) ) delete_fixup(ptst, s, x);
    }

    mcs_unlock(&s->writer_lock, &writer_qn);

    critical_exit(ptst);

    return ov;
}


setval_t set_lookup(set_t *s, setkey_t k)
{
    ptst_t  *ptst;
    node_t  *m, *n;
    mrsw_qnode_t qn[2], *m_pqn=&qn[0], *n_pqn=&qn[1], *t_pqn;
    setval_t v = NULL;

    k = CALLER_TO_INTERNAL_KEY(k);

    ptst = critical_enter();

    n = &s->root;
    rd_lock(&n->lock, n_pqn);

    while ( (m = (k < n->k) ? n->l : n->r) != &null )
    {
        rd_lock(&m->lock, m_pqn);
        rd_unlock(&n->lock, n_pqn);
        n = m;
        t_pqn = m_pqn;
        m_pqn = n_pqn;
        n_pqn = t_pqn;
        if ( k == n->k )
        {
            v = GET_VALUE(n->v);
            break;
        }
    }

    rd_unlock(&n->lock, n_pqn);

    critical_exit(ptst);

    return v;
}


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

    null.k = 0;
    null.v = MK_BLACK(NULL);
    null.l = NULL;
    null.r = NULL;
    null.p = NULL;
    mrsw_init(&null.lock);
}