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@polymtl.ca>
  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
  40 #ifdef __cplusplus
  41 extern "C" {
  42 #endif
  43
  44 /*
  45  * Number of entries in the per-thread defer queue. Must be power of 2.
  46  */
  47 #define DEFER_QUEUE_SIZE        (1 << 12)
  48 #define DEFER_QUEUE_MASK        (DEFER_QUEUE_SIZE - 1)
  49
  50 /*
  51  * Typically, data is aligned at least on the architecture size.
  52  * Use lowest bit to indicate that the current callback is changing.
  53  * Assumes that (void *)-2L is not used often. Used to encode non-aligned
  54  * functions and non-aligned data using extra space.
  55  * We encode the (void *)-2L fct as: -2L, fct, data.
  56  * We encode the (void *)-2L data as: -2L, fct, data.
  57  * Here, DQ_FCT_MARK == ~DQ_FCT_BIT. Required for the test order.
  58  */
  59 #define DQ_FCT_BIT              (1 << 0)
  60 #define DQ_IS_FCT_BIT(x)        ((unsigned long)(x) & DQ_FCT_BIT)
  61 #define DQ_SET_FCT_BIT(x)       \
  62         (x = (void *)((unsigned long)(x) | DQ_FCT_BIT))
  63 #define DQ_CLEAR_FCT_BIT(x)     \
  64         (x = (void *)((unsigned long)(x) & ~DQ_FCT_BIT))
  65 #define DQ_FCT_MARK             ((void *)(~DQ_FCT_BIT))
  66
  67 /*
  68  * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
  69  */
  70 #define _LOAD_SHARED(p)        ACCESS_ONCE(p)
  71
  72 /*
  73  * Load a data from shared memory, doing a cache flush if required.
  74  */
  75 #define LOAD_SHARED(p)                  \
  76         ({                              \
  77                 smp_rmc();              \
  78                 _LOAD_SHARED(p);        \
  79         })
  80
  81 /*
  82  * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
  83  */
  84 #define _STORE_SHARED(x, v)     ({ ACCESS_ONCE(x) = (v); })
  85
  86 /*
  87  * Store v into x, where x is located in shared memory. Performs the required
  88  * cache flush after writing. Returns v.
  89  */
  90 #define STORE_SHARED(x, v)              \
  91         ({                              \
  92                 _STORE_SHARED(x, v);    \
  93                 smp_wmc();              \
  94                 (v);                    \
  95         })
  96
  97 /*
  98  * This code section can only be included in LGPL 2.1 compatible source code.
  99  * See below for the function call wrappers which can be used in code meant to
 100  * be only linked with the Userspace RCU library. This comes with a small
 101  * performance degradation on the read-side due to the added function calls.
 102  * This is required to permit relinking with newer versions of the library.
 103  */
 104
 105 #ifdef DEBUG_RCU
 106 #define rcu_assert(args...)     assert(args)
 107 #else
 108 #define rcu_assert(args...)
 109 #endif
 110
 111 /*
 112  * defer queue.
 113  * Contains pointers. Encoded to save space when same callback is often used.
 114  * When looking up the next item:
 115  * - if DQ_FCT_BIT is set, set the current callback to DQ_CLEAR_FCT_BIT(ptr)
 116  *   - next element contains pointer to data.
 117  * - else if item == DQ_FCT_MARK
 118  *   - set the current callback to next element ptr
 119  *   - following next element contains pointer to data.
 120  * - else current element contains data
 121  */
 122 struct defer_queue {
 123         unsigned long head;     /* add element at head */
 124         void *last_fct_in;      /* last fct pointer encoded */
 125         unsigned long tail;     /* next element to remove at tail */
 126         void *last_fct_out;     /* last fct pointer encoded */
 127         void **q;
 128         /* registry information */
 129         unsigned long last_head;
 130         struct list_head list;  /* list of thread queues */
 131 };
 132
 133 #ifdef __cplusplus
 134 }
 135 #endif
 136
 137 #endif /* _URCU_DEFER_STATIC_H */