urcu-reclaim-static.h

   1 #ifndef _URCU_RECLAIM_STATIC_H
   2 #define _URCU_RECLAIM_STATIC_H
   3
   4 /*
   5  * urcu-static.h
   6  *
   7  * Userspace RCU header.
   8  *
   9  * TO BE INCLUDED ONLY IN LGPL-COMPATIBLE CODE. See urcu.h for linking
  10  * dynamically with the userspace rcu 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 <compiler.h>
  36 #include <arch.h>
  37
  38
  39 /*
  40  * Number of entries in the per-thread reclaim queue. Must be power of 2.
  41  */
  42 #define RECLAIM_QUEUE_SIZE      (1 << 12)
  43 #define RECLAIM_QUEUE_MASK      (RECLAIM_QUEUE_SIZE - 1)
  44
  45 /*
  46  * Identify a shared load. A smp_rmc() or smp_mc() should come before the load.
  47  */
  48 #define _LOAD_SHARED(p)        ACCESS_ONCE(p)
  49
  50 /*
  51  * Load a data from shared memory, doing a cache flush if required.
  52  */
  53 #define LOAD_SHARED(p)                  \
  54         ({                              \
  55                 smp_rmc();              \
  56                 _LOAD_SHARED(p);        \
  57         })
  58
  59 /*
  60  * Identify a shared store. A smp_wmc() or smp_mc() should follow the store.
  61  */
  62 #define _STORE_SHARED(x, v)     ({ ACCESS_ONCE(x) = (v); })
  63
  64 /*
  65  * Store v into x, where x is located in shared memory. Performs the required
  66  * cache flush after writing. Returns v.
  67  */
  68 #define STORE_SHARED(x, v)              \
  69         ({                              \
  70                 _STORE_SHARED(x, v);    \
  71                 smp_wmc();              \
  72                 (v);                    \
  73         })
  74
  75 /*
  76  * This code section can only be included in LGPL 2.1 compatible source code.
  77  * See below for the function call wrappers which can be used in code meant to
  78  * be only linked with the Userspace RCU library. This comes with a small
  79  * performance degradation on the read-side due to the added function calls.
  80  * This is required to permit relinking with newer versions of the library.
  81  */
  82
  83 #ifdef DEBUG_RCU
  84 #define rcu_assert(args...)     assert(args)
  85 #else
  86 #define rcu_assert(args...)
  87 #endif
  88
  89 struct reclaim_queue {
  90         unsigned long head;     /* add element at head */
  91         unsigned long tail;     /* next element to remove at tail */
  92         void **q;
  93 };
  94
  95 extern struct reclaim_queue __thread reclaim_queue;
  96
  97 extern void rcu_reclaim_barrier_thread(void);
  98
  99 /*
 100  * not signal-safe.
 101  */
 102 static inline void _rcu_reclaim_queue(void *p)
 103 {
 104         unsigned long head, tail;
 105
 106         /*
 107          * Head is only modified by ourself. Tail can be modified by reclamation
 108          * thread.
 109          */
 110         head = reclaim_queue.head;
 111         tail = LOAD_SHARED(reclaim_queue.tail);
 112
 113         /*
 114          * If queue is full, empty it ourself.
 115          */
 116         if (unlikely(head - tail >= RECLAIM_QUEUE_SIZE)) {
 117                 assert(head - tail == RECLAIM_QUEUE_SIZE);
 118                 rcu_reclaim_barrier_thread();
 119                 assert(head - LOAD_SHARED(reclaim_queue.tail) == 0);
 120         }
 121
 122         smp_wmb();      /* Publish new pointer before write q[] */
 123         _STORE_SHARED(reclaim_queue.q[head & RECLAIM_QUEUE_MASK], p);
 124         smp_wmb();      /* Write q[] before head. */
 125         STORE_SHARED(reclaim_queue.head, head + 1);
 126 }
 127
 128 #endif /* _URCU_RECLAIM_STATIC_H */