urcu-defer-static.h

   1 #ifndef _URCU_DEFER_STATIC_H
   2 #define _URCU_DEFER_STATIC_H
   3
   4 /*
   5  * urcu-defer-static.h
   6  *
   7  * Userspace RCU header - memory reclamation.
   8  *
   9  * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu-defer.h for linking
  10  * dynamically with the userspace rcu reclamation library.
  11  *
  12  * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  13  * Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
  14  *
  15  * This library is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU Lesser General Public
  17  * License as published by the Free Software Foundation; either
  18  * version 2.1 of the License, or (at your option) any later version.
  19  *
  20  * This library is distributed in the hope that it will be useful,
  21  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  22  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  23  * Lesser General Public License for more details.
  24  *
  25  * You should have received a copy of the GNU Lesser General Public
  26  * License along with this library; if not, write to the Free Software
  27  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  28  *
  29  * IBM's contributions to this file may be relicensed under LGPLv2 or later.
  30  */
  31
  32 #include <stdlib.h>
  33 #include <pthread.h>
  34
  35 #include <urcu/compiler.h>
  36 #include <urcu/arch.h>
  37 #include <urcu/uatomic_arch.h>
  38 #include <urcu/list.h>
  39 #include <urcu/system.h>
  40
  41 #ifdef __cplusplus
  42 extern "C" {
  43 #endif
  44
  45 /*
  46  * Number of entries in the per-thread defer queue. Must be power of 2.
  47  */
  48 #define DEFER_QUEUE_SIZE        (1 << 12)
  49 #define DEFER_QUEUE_MASK        (DEFER_QUEUE_SIZE - 1)
  50
  51 /*
  52  * Typically, data is aligned at least on the architecture size.
  53  * Use lowest bit to indicate that the current callback is changing.
  54  * Assumes that (void *)-2L is not used often. Used to encode non-aligned
  55  * functions and non-aligned data using extra space.
  56  * We encode the (void *)-2L fct as: -2L, fct, data.
  57  * We encode the (void *)-2L data as: -2L, fct, data.
  58  * Here, DQ_FCT_MARK == ~DQ_FCT_BIT. Required for the test order.
  59  */
  60 #define DQ_FCT_BIT              (1 << 0)
  61 #define DQ_IS_FCT_BIT(x)        ((unsigned long)(x) & DQ_FCT_BIT)
  62 #define DQ_SET_FCT_BIT(x)       \
  63         (x = (void *)((unsigned long)(x) | DQ_FCT_BIT))
  64 #define DQ_CLEAR_FCT_BIT(x)     \
  65         (x = (void *)((unsigned long)(x) & ~DQ_FCT_BIT))
  66 #define DQ_FCT_MARK             ((void *)(~DQ_FCT_BIT))
  67
  68 /*
  69  * This code section can only be included in LGPL 2.1 compatible source code.
  70  * See below for the function call wrappers which can be used in code meant to
  71  * be only linked with the Userspace RCU library. This comes with a small
  72  * performance degradation on the read-side due to the added function calls.
  73  * This is required to permit relinking with newer versions of the library.
  74  */
  75
  76 #ifdef DEBUG_RCU
  77 #define rcu_assert(args...)     assert(args)
  78 #else
  79 #define rcu_assert(args...)
  80 #endif
  81
  82 /*
  83  * defer queue.
  84  * Contains pointers. Encoded to save space when same callback is often used.
  85  * When looking up the next item:
  86  * - if DQ_FCT_BIT is set, set the current callback to DQ_CLEAR_FCT_BIT(ptr)
  87  *   - next element contains pointer to data.
  88  * - else if item == DQ_FCT_MARK
  89  *   - set the current callback to next element ptr
  90  *   - following next element contains pointer to data.
  91  * - else current element contains data
  92  */
  93 struct defer_queue {
  94         unsigned long head;     /* add element at head */
  95         void *last_fct_in;      /* last fct pointer encoded */
  96         unsigned long tail;     /* next element to remove at tail */
  97         void *last_fct_out;     /* last fct pointer encoded */
  98         void **q;
  99         /* registry information */
 100         unsigned long last_head;
 101         struct list_head list;  /* list of thread queues */
 102 };
 103
 104 #ifdef __cplusplus
 105 }
 106 #endif
 107
 108 #endif /* _URCU_DEFER_STATIC_H */