kernel/rcu/rcu.h - linux - Git at Google

 /*
  * 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, you can access it online at
  * http://www.gnu.org/licenses/gpl-2.0.html.
  *
  * Copyright IBM Corporation, 2011
  *
  * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  */

 #ifndef __LINUX_RCU_H
 #define __LINUX_RCU_H

 #include <trace/events/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)


 /*
  * Grace-period counter management.
  */

 /* Adjust sequence number for start of update-side operation. */
 static inline void rcu_seq_start(unsigned long *sp)
 {
 	WRITE_ONCE(*sp, *sp + 1);
 	smp_mb(); /* Ensure update-side operation after counter increment. */
 	WARN_ON_ONCE(!(*sp & 0x1));
 }

 /* Adjust sequence number for end of update-side operation. */
 static inline void rcu_seq_end(unsigned long *sp)
 {
 	smp_mb(); /* Ensure update-side operation before counter increment. */
 	WARN_ON_ONCE(!(*sp & 0x1));
 	WRITE_ONCE(*sp, *sp + 1);
 }

 /* Take a snapshot of the update side's sequence number. */
 static inline unsigned long rcu_seq_snap(unsigned long *sp)
 {
 	unsigned long s;

 	s = (READ_ONCE(*sp) + 3) & ~0x1;
 	smp_mb(); /* Above access must not bleed into critical section. */
 	return s;
 }

 /* Return the current value the update side's sequence number, no ordering. */
 static inline unsigned long rcu_seq_current(unsigned long *sp)
 {
 	return READ_ONCE(*sp);
 }

 /*
  * Given a snapshot from rcu_seq_snap(), determine whether or not a
  * full update-side operation has occurred.
  */
 static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
 {
 	return ULONG_CMP_GE(READ_ONCE(*sp), s);
 }

 /*
  * 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 int debug_rcu_head_queue(struct rcu_head *head)
 {
 	int r1;

 	r1 = debug_object_activate(head, &rcuhead_debug_descr);
 	debug_object_active_state(head, &rcuhead_debug_descr,
 				  STATE_RCU_HEAD_READY,
 				  STATE_RCU_HEAD_QUEUED);
 	return r1;
 }

 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 int debug_rcu_head_queue(struct rcu_head *head)
 {
 	return 0;
 }

 static inline void debug_rcu_head_unqueue(struct rcu_head *head)
 {
 }
 #endif	/* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */

 void kfree(const void *);

 /*
  * Reclaim the specified callback, either by invoking it (non-lazy case)
  * or freeing it directly (lazy case).  Return true if lazy, false otherwise.
  */
 static inline bool __rcu_reclaim(const char *rn, struct rcu_head *head)
 {
 	unsigned long offset = (unsigned long)head->func;

 	rcu_lock_acquire(&rcu_callback_map);
 	if (__is_kfree_rcu_offset(offset)) {
 		RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
 		kfree((void *)head - offset);
 		rcu_lock_release(&rcu_callback_map);
 		return true;
 	} else {
 		RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
 		head->func(head);
 		rcu_lock_release(&rcu_callback_map);
 		return false;
 	}
 }

 #ifdef CONFIG_RCU_STALL_COMMON

 extern int rcu_cpu_stall_suppress;
 int rcu_jiffies_till_stall_check(void);

 #endif /* #ifdef CONFIG_RCU_STALL_COMMON */

 /*
  * Strings used in tracepoints need to be exported via the
  * tracing system such that tools like perf and trace-cmd can
  * translate the string address pointers to actual text.
  */
 #define TPS(x)  tracepoint_string(x)

 void rcu_early_boot_tests(void);
 void rcu_test_sync_prims(void);

 /*
  * This function really isn't for public consumption, but RCU is special in
  * that context switches can allow the state machine to make progress.
  */
 extern void resched_cpu(int cpu);

 #if defined(SRCU) || !defined(TINY_RCU)

 #include <linux/rcu_node_tree.h>

 extern int rcu_num_lvls;
 extern int rcu_num_nodes;
 static bool rcu_fanout_exact;
 static int rcu_fanout_leaf;

 /*
  * Compute the per-level fanout, either using the exact fanout specified
  * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
  */
 static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
 {
 	int i;

 	if (rcu_fanout_exact) {
 		levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
 		for (i = rcu_num_lvls - 2; i >= 0; i--)
 			levelspread[i] = RCU_FANOUT;
 	} else {
 		int ccur;
 		int cprv;

 		cprv = nr_cpu_ids;
 		for (i = rcu_num_lvls - 1; i >= 0; i--) {
 			ccur = levelcnt[i];
 			levelspread[i] = (cprv + ccur - 1) / ccur;
 			cprv = ccur;
 		}
 	}
 }

 /*
  * Do a full breadth-first scan of the rcu_node structures for the
  * specified rcu_state structure.
  */
 #define rcu_for_each_node_breadth_first(rsp, rnp) \
 	for ((rnp) = &(rsp)->node[0]; \
 	     (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)

 /*
  * Do a breadth-first scan of the non-leaf rcu_node structures for the
  * specified rcu_state structure.  Note that if there is a singleton
  * rcu_node tree with but one rcu_node structure, this loop is a no-op.
  */
 #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
 	for ((rnp) = &(rsp)->node[0]; \
 	     (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)

 /*
  * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
  * structure.  Note that if there is a singleton rcu_node tree with but
  * one rcu_node structure, this loop -will- visit the rcu_node structure.
  * It is still a leaf node, even if it is also the root node.
  */
 #define rcu_for_each_leaf_node(rsp, rnp) \
 	for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
 	     (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)

 /*
  * Iterate over all possible CPUs in a leaf RCU node.
  */
 #define for_each_leaf_node_possible_cpu(rnp, cpu) \
 	for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \
 	     cpu <= rnp->grphi; \
 	     cpu = cpumask_next((cpu), cpu_possible_mask))

 #endif /* #if defined(SRCU) || !defined(TINY_RCU) */

 #endif /* __LINUX_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, you can access it online at
	* http://www.gnu.org/licenses/gpl-2.0.html.
	*
	* Copyright IBM Corporation, 2011
	*
	* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
	*/

	#ifndef __LINUX_RCU_H
	#define __LINUX_RCU_H

	#include <trace/events/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)


	/*
	* Grace-period counter management.
	*/

	/* Adjust sequence number for start of update-side operation. */
	static inline void rcu_seq_start(unsigned long *sp)
	{
	WRITE_ONCE(sp, sp + 1);
	smp_mb(); /* Ensure update-side operation after counter increment. */
	WARN_ON_ONCE(!(*sp & 0x1));
	}

	/* Adjust sequence number for end of update-side operation. */
	static inline void rcu_seq_end(unsigned long *sp)
	{
	smp_mb(); /* Ensure update-side operation before counter increment. */
	WARN_ON_ONCE(!(*sp & 0x1));
	WRITE_ONCE(sp, sp + 1);
	}

	/* Take a snapshot of the update side's sequence number. */
	static inline unsigned long rcu_seq_snap(unsigned long *sp)
	{
	unsigned long s;

	s = (READ_ONCE(*sp) + 3) & ~0x1;
	smp_mb(); /* Above access must not bleed into critical section. */
	return s;
	}

	/* Return the current value the update side's sequence number, no ordering. */
	static inline unsigned long rcu_seq_current(unsigned long *sp)
	{
	return READ_ONCE(*sp);
	}

	/*
	* Given a snapshot from rcu_seq_snap(), determine whether or not a
	* full update-side operation has occurred.
	*/
	static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
	{
	return ULONG_CMP_GE(READ_ONCE(*sp), s);
	}

	/*
	* 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 int debug_rcu_head_queue(struct rcu_head *head)
	{
	int r1;

	r1 = debug_object_activate(head, &rcuhead_debug_descr);
	debug_object_active_state(head, &rcuhead_debug_descr,
	STATE_RCU_HEAD_READY,
	STATE_RCU_HEAD_QUEUED);
	return r1;
	}

	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 int debug_rcu_head_queue(struct rcu_head *head)
	{
	return 0;
	}

	static inline void debug_rcu_head_unqueue(struct rcu_head *head)
	{
	}
	#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */

	void kfree(const void *);

	/*
	* Reclaim the specified callback, either by invoking it (non-lazy case)
	* or freeing it directly (lazy case). Return true if lazy, false otherwise.
	*/
	static inline bool __rcu_reclaim(const char rn, struct rcu_head head)
	{
	unsigned long offset = (unsigned long)head->func;

	rcu_lock_acquire(&rcu_callback_map);
	if (__is_kfree_rcu_offset(offset)) {
	RCU_TRACE(trace_rcu_invoke_kfree_callback(rn, head, offset);)
	kfree((void *)head - offset);
	rcu_lock_release(&rcu_callback_map);
	return true;
	} else {
	RCU_TRACE(trace_rcu_invoke_callback(rn, head);)
	head->func(head);
	rcu_lock_release(&rcu_callback_map);
	return false;
	}
	}

	#ifdef CONFIG_RCU_STALL_COMMON

	extern int rcu_cpu_stall_suppress;
	int rcu_jiffies_till_stall_check(void);

	#endif /* #ifdef CONFIG_RCU_STALL_COMMON */

	/*
	* Strings used in tracepoints need to be exported via the
	* tracing system such that tools like perf and trace-cmd can
	* translate the string address pointers to actual text.
	*/
	#define TPS(x) tracepoint_string(x)

	void rcu_early_boot_tests(void);
	void rcu_test_sync_prims(void);

	/*
	* This function really isn't for public consumption, but RCU is special in
	* that context switches can allow the state machine to make progress.
	*/
	extern void resched_cpu(int cpu);

	#if defined(SRCU) \|\| !defined(TINY_RCU)

	#include <linux/rcu_node_tree.h>

	extern int rcu_num_lvls;
	extern int rcu_num_nodes;
	static bool rcu_fanout_exact;
	static int rcu_fanout_leaf;

	/*
	* Compute the per-level fanout, either using the exact fanout specified
	* or balancing the tree, depending on the rcu_fanout_exact boot parameter.
	*/
	static inline void rcu_init_levelspread(int levelspread, const int levelcnt)
	{
	int i;

	if (rcu_fanout_exact) {
	levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
	for (i = rcu_num_lvls - 2; i >= 0; i--)
	levelspread[i] = RCU_FANOUT;
	} else {
	int ccur;
	int cprv;

	cprv = nr_cpu_ids;
	for (i = rcu_num_lvls - 1; i >= 0; i--) {
	ccur = levelcnt[i];
	levelspread[i] = (cprv + ccur - 1) / ccur;
	cprv = ccur;
	}
	}
	}

	/*
	* Do a full breadth-first scan of the rcu_node structures for the
	* specified rcu_state structure.
	*/
	#define rcu_for_each_node_breadth_first(rsp, rnp) \
	for ((rnp) = &(rsp)->node[0]; \
	(rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)

	/*
	* Do a breadth-first scan of the non-leaf rcu_node structures for the
	* specified rcu_state structure. Note that if there is a singleton
	* rcu_node tree with but one rcu_node structure, this loop is a no-op.
	*/
	#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
	for ((rnp) = &(rsp)->node[0]; \
	(rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)

	/*
	* Scan the leaves of the rcu_node hierarchy for the specified rcu_state
	* structure. Note that if there is a singleton rcu_node tree with but
	* one rcu_node structure, this loop -will- visit the rcu_node structure.
	* It is still a leaf node, even if it is also the root node.
	*/
	#define rcu_for_each_leaf_node(rsp, rnp) \
	for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
	(rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)

	/*
	* Iterate over all possible CPUs in a leaf RCU node.
	*/
	#define for_each_leaf_node_possible_cpu(rnp, cpu) \
	for ((cpu) = cpumask_next(rnp->grplo - 1, cpu_possible_mask); \
	cpu <= rnp->grphi; \
	cpu = cpumask_next((cpu), cpu_possible_mask))

	#endif /* #if defined(SRCU) \|\| !defined(TINY_RCU) */

	#endif /* __LINUX_RCU_H */