1/*
  2 * Read-Copy Update definitions shared among RCU implementations.
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License as published by
  6 * the Free Software Foundation; either version 2 of the License, or
  7 * (at your option) any later version.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 *
 14 * You should have received a copy of the GNU General Public License
 15 * along with this program; if not, write to the Free Software
 16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 17 *
 18 * Copyright IBM Corporation, 2011
 19 *
 20 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 21 */
 22
 23#ifndef __LINUX_RCU_H
 24#define __LINUX_RCU_H
 25
 26#ifdef CONFIG_RCU_TRACE
 27#define RCU_TRACE(stmt) stmt
 28#else /* #ifdef CONFIG_RCU_TRACE */
 29#define RCU_TRACE(stmt)
 30#endif /* #else #ifdef CONFIG_RCU_TRACE */
 31
 32/*
 33 * Process-level increment to ->dynticks_nesting field.  This allows for
 34 * architectures that use half-interrupts and half-exceptions from
 35 * process context.
 36 *
 37 * DYNTICK_TASK_NEST_MASK defines a field of width DYNTICK_TASK_NEST_WIDTH
 38 * that counts the number of process-based reasons why RCU cannot
 39 * consider the corresponding CPU to be idle, and DYNTICK_TASK_NEST_VALUE
 40 * is the value used to increment or decrement this field.
 41 *
 42 * The rest of the bits could in principle be used to count interrupts,
 43 * but this would mean that a negative-one value in the interrupt
 44 * field could incorrectly zero out the DYNTICK_TASK_NEST_MASK field.
 45 * We therefore provide a two-bit guard field defined by DYNTICK_TASK_MASK
 46 * that is set to DYNTICK_TASK_FLAG upon initial exit from idle.
 47 * The DYNTICK_TASK_EXIT_IDLE value is thus the combined value used upon
 48 * initial exit from idle.
 49 */
 50#define DYNTICK_TASK_NEST_WIDTH 7
 51#define DYNTICK_TASK_NEST_VALUE ((LLONG_MAX >> DYNTICK_TASK_NEST_WIDTH) + 1)
 52#define DYNTICK_TASK_NEST_MASK  (LLONG_MAX - DYNTICK_TASK_NEST_VALUE + 1)
 53#define DYNTICK_TASK_FLAG	   ((DYNTICK_TASK_NEST_VALUE / 8) * 2)
 54#define DYNTICK_TASK_MASK	   ((DYNTICK_TASK_NEST_VALUE / 8) * 3)
 55#define DYNTICK_TASK_EXIT_IDLE	   (DYNTICK_TASK_NEST_VALUE + \
 56				    DYNTICK_TASK_FLAG)
 57
 58/*
 59 * debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
 60 * by call_rcu() and rcu callback execution, and are therefore not part of the
 61 * RCU API. Leaving in rcupdate.h because they are used by all RCU flavors.
 62 */
 63
 64#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
 65# define STATE_RCU_HEAD_READY	0
 66# define STATE_RCU_HEAD_QUEUED	1
 67
 68extern struct debug_obj_descr rcuhead_debug_descr;
 69
 70static inline void debug_rcu_head_queue(struct rcu_head *head)
 71{
 72	debug_object_activate(head, &rcuhead_debug_descr);
 73	debug_object_active_state(head, &rcuhead_debug_descr,
 74				  STATE_RCU_HEAD_READY,
 75				  STATE_RCU_HEAD_QUEUED);
 76}
 77
 78static inline void debug_rcu_head_unqueue(struct rcu_head *head)
 79{
 80	debug_object_active_state(head, &rcuhead_debug_descr,
 81				  STATE_RCU_HEAD_QUEUED,
 82				  STATE_RCU_HEAD_READY);
 83	debug_object_deactivate(head, &rcuhead_debug_descr);
 84}
 85#else	/* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 86static inline void debug_rcu_head_queue(struct rcu_head *head)
 87{
 88}
 89
 90static inline void debug_rcu_head_unqueue(struct rcu_head *head)
 91{
 92}
 93#endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 94
 95extern void kfree(const void *);
 96
 97static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
 98{
 99	unsigned long offset = (unsigned long)head->func;
100
101	if (__is_kfree_rcu_offset(offset)) {
102		RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset));
103		kfree((void *)head - offset);
104		return 1;
105	} else {
106		RCU_TRACE(trace_rcu_invoke_callback(rn, head));
107		head->func(head);
108		return 0;
109	}
110}
111
112#endif /* __LINUX_RCU_H */