FreeBSD/Linux Kernel Cross Reference
sys/kernel/rcu.h

     /*
      * Read-Copy Update definitions shared among RCU implementations.
      *
      * This program is free software; you can redistribute it and/or modify
      * it under the terms of the GNU General Public License as published by
      * the Free Software Foundation; either version 2 of the License, or
      * (at your option) any later version.
      *
      * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU General Public License for more details.
     *
     * You should have received a copy of the GNU General Public License
     * along with this program; if not, write to the Free Software
     * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
     *
     * Copyright IBM Corporation, 2011
     *
     * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
     */
    
    #ifndef __LINUX_RCU_H
    #define __LINUX_RCU_H
    
    #ifdef CONFIG_RCU_TRACE
    #define RCU_TRACE(stmt) stmt
    #else /* #ifdef CONFIG_RCU_TRACE */
    #define RCU_TRACE(stmt)
    #endif /* #else #ifdef CONFIG_RCU_TRACE */
    
    /*
     * Process-level increment to ->dynticks_nesting field.  This allows for
     * architectures that use half-interrupts and half-exceptions from
     * process context.
     *
     * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
     * that counts the number of process-based reasons why RCU cannot
     * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
     * is the value used to increment or decrement this field.
     *
     * The rest of the bits could in principle be used to count interrupts,
     * but this would mean that a negative-one value in the interrupt
     * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
     * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
     * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
     * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
     * initial exit from idle.
     */
    #define DYNTICK_TASK_NEST_WIDTH 7
    #define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
    #define DYNTICK_TASK_NEST_MASK  (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
    #define DYNTICK_TASK_FLAG          ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
    #define DYNTICK_TASK_MASK          ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
    #define DYNTICK_TASK_EXIT_IDLE     (DYNTICK_TASK_NEST_VALUE + \
                                        DYNTICK_TASK_FLAG)
    
    /*
     * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
     * by call_rcu() and rcu callback execution, and are therefore not part of the
     * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
     */
    
    #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
    # define STATE_RCU_HEAD_READY   0
    # define STATE_RCU_HEAD_QUEUED  1
    
    extern struct debug_obj_descr rcuhead_debug_descr;
    
    static inline void debug_rcu_head_queue(struct rcu_head *head)
    {
            debug_object_activate(head, &rcuhead_debug_descr);
            debug_object_active_state(head, &rcuhead_debug_descr,
                                      STATE_RCU_HEAD_READY,
                                      STATE_RCU_HEAD_QUEUED);
    }
    
    static inline void debug_rcu_head_unqueue(struct rcu_head *head)
    {
            debug_object_active_state(head, &rcuhead_debug_descr,
                                      STATE_RCU_HEAD_QUEUED,
                                      STATE_RCU_HEAD_READY);
            debug_object_deactivate(head, &rcuhead_debug_descr);
    }
    #else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
    static inline void debug_rcu_head_queue(struct rcu_head *head)
    {
    }
    
    static inline void debug_rcu_head_unqueue(struct rcu_head *head)
    {
    }
    #endif  /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
    
    extern void kfree(const void *);
    
    static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
    {
            unsigned long offset = (unsigned long)head->func;
   
           if (__is_kfree_rcu_offset(offset)) {
                   RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
                   kfree((void *)head - offset);
                   return 1;
           } else {
                   RCU_TRACE(trace_rcu_invoke_callback(rn, head));
                   head->func(head);
                   return 0;
           }
   }
   
   extern int rcu_expedited;
   
   #endif /* __LINUX_RCU_H */

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