FreeBSD/Linux Kernel Cross Reference
sys/dev/cxgbe/iw_cxgbe/id_table.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2011-2013 Chelsio Communications.  All rights reserved.
      *
      * This software is available to you under a choice of one of two
      * licenses.  You may choose to be licensed under the terms of the GNU
      * General Public License (GPL) Version 2, available from the file
      * COPYING in the main directory of this source tree, or the
     * OpenIB.org BSD license below:
     *
     *     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.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
     * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
     * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     * SOFTWARE.
     */
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_inet.h"
    
    #ifdef TCP_OFFLOAD
    #include <sys/libkern.h>
    #include "iw_cxgbe.h"
    
    #define RANDOM_SKIP 16
    
    /*
     * Trivial bitmap-based allocator. If the random flag is set, the
     * allocator is designed to:
     * - pseudo-randomize the id returned such that it is not trivially predictable.
     * - avoid reuse of recently used id (at the expense of predictability)
     */
    u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
    {
            unsigned long flags;
            u32 obj;
    
            spin_lock_irqsave(&alloc->lock, flags);
    
            obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
            if (obj >= alloc->max)
                    obj = find_first_zero_bit(alloc->table, alloc->max);
    
            if (obj < alloc->max) {
                    if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
                            alloc->last += arc4random() % RANDOM_SKIP;
                    else
                            alloc->last = obj + 1;
                    if (alloc->last >= alloc->max)
                            alloc->last = 0;
                    set_bit(obj, alloc->table);
                    obj += alloc->start;
            } else
                    obj = -1;
    
            spin_unlock_irqrestore(&alloc->lock, flags);
            return obj;
    }
    
    void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
    {
            unsigned long flags;
    
            obj -= alloc->start;
            BUG_ON((int)obj < 0);
    
            spin_lock_irqsave(&alloc->lock, flags);
            clear_bit(obj, alloc->table);
            spin_unlock_irqrestore(&alloc->lock, flags);
    }
    
    int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
                            u32 reserved, u32 flags)
    {
            int i;
    
            alloc->start = start;
            alloc->flags = flags;
            if (flags & C4IW_ID_TABLE_F_RANDOM)
                    alloc->last = arc4random() % RANDOM_SKIP;
            else
                   alloc->last = 0;
           alloc->max  = num;
           spin_lock_init(&alloc->lock);
           alloc->table = kmalloc(BITS_TO_LONGS(num) * sizeof(long),
                                   GFP_KERNEL);
           if (!alloc->table)
                   return -ENOMEM;
   
           bitmap_zero(alloc->table, num);
           if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
                   for (i = 0; i < reserved; ++i)
                           set_bit(i, alloc->table);
   
           return 0;
   }
   
   void c4iw_id_table_free(struct c4iw_id_table *alloc)
   {
           kfree(alloc->table);
   }
   #endif

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