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Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001/*
2 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
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, 2008
19 *
20 * Author: Dipankar Sarma <dipankar@in.ibm.com>
21 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical algorithm
22 *
23 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
24 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
25 *
26 * For detailed explanation of Read-Copy Update mechanism see -
27 * Documentation/RCU
28 */
29
30#ifndef __LINUX_RCUTREE_H
31#define __LINUX_RCUTREE_H
32
33#include <linux/cache.h>
34#include <linux/spinlock.h>
35#include <linux/threads.h>
Paul E. McKenney64db4cf2008-12-18 21:55:32 +010036#include <linux/cpumask.h>
37#include <linux/seqlock.h>
38
39/*
40 * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
41 * In theory, it should be possible to add more levels straightforwardly.
42 * In practice, this has not been tested, so there is probably some
43 * bug somewhere.
44 */
45#define MAX_RCU_LVLS 3
46#define RCU_FANOUT (CONFIG_RCU_FANOUT)
47#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
48#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)
49
50#if NR_CPUS <= RCU_FANOUT
51# define NUM_RCU_LVLS 1
52# define NUM_RCU_LVL_0 1
53# define NUM_RCU_LVL_1 (NR_CPUS)
54# define NUM_RCU_LVL_2 0
55# define NUM_RCU_LVL_3 0
56#elif NR_CPUS <= RCU_FANOUT_SQ
57# define NUM_RCU_LVLS 2
58# define NUM_RCU_LVL_0 1
59# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT)
60# define NUM_RCU_LVL_2 (NR_CPUS)
61# define NUM_RCU_LVL_3 0
62#elif NR_CPUS <= RCU_FANOUT_CUBE
63# define NUM_RCU_LVLS 3
64# define NUM_RCU_LVL_0 1
65# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ)
66# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT))
67# define NUM_RCU_LVL_3 NR_CPUS
68#else
69# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
70#endif /* #if (NR_CPUS) <= RCU_FANOUT */
71
72#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
73#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
74
75/*
76 * Dynticks per-CPU state.
77 */
78struct rcu_dynticks {
79 int dynticks_nesting; /* Track nesting level, sort of. */
80 int dynticks; /* Even value for dynticks-idle, else odd. */
81 int dynticks_nmi; /* Even value for either dynticks-idle or */
82 /* not in nmi handler, else odd. So this */
83 /* remains even for nmi from irq handler. */
84};
85
86/*
87 * Definition for node within the RCU grace-period-detection hierarchy.
88 */
89struct rcu_node {
90 spinlock_t lock;
91 unsigned long qsmask; /* CPUs or groups that need to switch in */
92 /* order for current grace period to proceed.*/
93 unsigned long qsmaskinit;
94 /* Per-GP initialization for qsmask. */
95 unsigned long grpmask; /* Mask to apply to parent qsmask. */
96 int grplo; /* lowest-numbered CPU or group here. */
97 int grphi; /* highest-numbered CPU or group here. */
98 u8 grpnum; /* CPU/group number for next level up. */
99 u8 level; /* root is at level 0. */
100 struct rcu_node *parent;
101} ____cacheline_internodealigned_in_smp;
102
103/* Index values for nxttail array in struct rcu_data. */
104#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
105#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
106#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
107#define RCU_NEXT_TAIL 3
108#define RCU_NEXT_SIZE 4
109
110/* Per-CPU data for read-copy update. */
111struct rcu_data {
112 /* 1) quiescent-state and grace-period handling : */
113 long completed; /* Track rsp->completed gp number */
114 /* in order to detect GP end. */
115 long gpnum; /* Highest gp number that this CPU */
116 /* is aware of having started. */
117 long passed_quiesc_completed;
118 /* Value of completed at time of qs. */
119 bool passed_quiesc; /* User-mode/idle loop etc. */
120 bool qs_pending; /* Core waits for quiesc state. */
121 bool beenonline; /* CPU online at least once. */
122 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
123 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
124
125 /* 2) batch handling */
126 /*
127 * If nxtlist is not NULL, it is partitioned as follows.
128 * Any of the partitions might be empty, in which case the
129 * pointer to that partition will be equal to the pointer for
130 * the following partition. When the list is empty, all of
131 * the nxttail elements point to nxtlist, which is NULL.
132 *
133 * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]):
134 * Entries that might have arrived after current GP ended
135 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
136 * Entries known to have arrived before current GP ended
137 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
138 * Entries that batch # <= ->completed - 1: waiting for current GP
139 * [nxtlist, *nxttail[RCU_DONE_TAIL]):
140 * Entries that batch # <= ->completed
141 * The grace period for these entries has completed, and
142 * the other grace-period-completed entries may be moved
143 * here temporarily in rcu_process_callbacks().
144 */
145 struct rcu_head *nxtlist;
146 struct rcu_head **nxttail[RCU_NEXT_SIZE];
147 long qlen; /* # of queued callbacks */
148 long blimit; /* Upper limit on a processed batch */
149
150#ifdef CONFIG_NO_HZ
151 /* 3) dynticks interface. */
152 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
153 int dynticks_snap; /* Per-GP tracking for dynticks. */
154 int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */
155#endif /* #ifdef CONFIG_NO_HZ */
156
157 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
158#ifdef CONFIG_NO_HZ
159 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
160#endif /* #ifdef CONFIG_NO_HZ */
161 unsigned long offline_fqs; /* Kicked due to being offline. */
162 unsigned long resched_ipi; /* Sent a resched IPI. */
163
Paul E. McKenneyef631b02009-04-13 21:31:16 -0700164 /* 5) For future __rcu_pending statistics. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100165 long n_rcu_pending; /* rcu_pending() calls since boot. */
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100166
167 int cpu;
168};
169
170/* Values for signaled field in struct rcu_state. */
171#define RCU_GP_INIT 0 /* Grace period being initialized. */
172#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */
173#define RCU_FORCE_QS 2 /* Need to force quiescent state. */
174#ifdef CONFIG_NO_HZ
175#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
176#else /* #ifdef CONFIG_NO_HZ */
177#define RCU_SIGNAL_INIT RCU_FORCE_QS
178#endif /* #else #ifdef CONFIG_NO_HZ */
179
180#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
181#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
182#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */
183#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */
184#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
185 /* to take at least one */
186 /* scheduling clock irq */
187 /* before ratting on them. */
188
189#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
190
191/*
192 * RCU global state, including node hierarchy. This hierarchy is
193 * represented in "heap" form in a dense array. The root (first level)
194 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
195 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
196 * and the third level in ->node[m+1] and following (->node[m+1] referenced
197 * by ->level[2]). The number of levels is determined by the number of
198 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
199 * consisting of a single rcu_node.
200 */
201struct rcu_state {
202 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
203 struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */
204 u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
205 u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */
206 struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */
207
208 /* The following fields are guarded by the root rcu_node's lock. */
209
210 u8 signaled ____cacheline_internodealigned_in_smp;
211 /* Force QS state. */
212 long gpnum; /* Current gp number. */
213 long completed; /* # of last completed gp. */
214 spinlock_t onofflock; /* exclude on/offline and */
215 /* starting new GP. */
216 spinlock_t fqslock; /* Only one task forcing */
217 /* quiescent states. */
218 unsigned long jiffies_force_qs; /* Time at which to invoke */
219 /* force_quiescent_state(). */
220 unsigned long n_force_qs; /* Number of calls to */
221 /* force_quiescent_state(). */
222 unsigned long n_force_qs_lh; /* ~Number of calls leaving */
223 /* due to lock unavailable. */
224 unsigned long n_force_qs_ngp; /* Number of calls leaving */
225 /* due to no GP active. */
226#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
227 unsigned long gp_start; /* Time at which GP started, */
228 /* but in jiffies. */
229 unsigned long jiffies_stall; /* Time at which to check */
230 /* for CPU stalls. */
231#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
232#ifdef CONFIG_NO_HZ
233 long dynticks_completed; /* Value of completed @ snap. */
234#endif /* #ifdef CONFIG_NO_HZ */
235};
236
Ingo Molnarb1f77b02009-03-13 03:20:49 +0100237extern void rcu_qsctr_inc(int cpu);
238extern void rcu_bh_qsctr_inc(int cpu);
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100239
240extern int rcu_pending(int cpu);
241extern int rcu_needs_cpu(int cpu);
242
243#ifdef CONFIG_DEBUG_LOCK_ALLOC
244extern struct lockdep_map rcu_lock_map;
245# define rcu_read_acquire() \
246 lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
247# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
248#else
249# define rcu_read_acquire() do { } while (0)
250# define rcu_read_release() do { } while (0)
251#endif
252
253static inline void __rcu_read_lock(void)
254{
255 preempt_disable();
256 __acquire(RCU);
257 rcu_read_acquire();
258}
259static inline void __rcu_read_unlock(void)
260{
261 rcu_read_release();
262 __release(RCU);
263 preempt_enable();
264}
265static inline void __rcu_read_lock_bh(void)
266{
267 local_bh_disable();
268 __acquire(RCU_BH);
269 rcu_read_acquire();
270}
271static inline void __rcu_read_unlock_bh(void)
272{
273 rcu_read_release();
274 __release(RCU_BH);
275 local_bh_enable();
276}
277
278#define __synchronize_sched() synchronize_rcu()
279
280#define call_rcu_sched(head, func) call_rcu(head, func)
281
282static inline void rcu_init_sched(void)
283{
284}
285
286extern void __rcu_init(void);
287extern void rcu_check_callbacks(int cpu, int user);
288extern void rcu_restart_cpu(int cpu);
289
290extern long rcu_batches_completed(void);
291extern long rcu_batches_completed_bh(void);
292
293#ifdef CONFIG_NO_HZ
294void rcu_enter_nohz(void);
295void rcu_exit_nohz(void);
296#else /* CONFIG_NO_HZ */
297static inline void rcu_enter_nohz(void)
298{
299}
300static inline void rcu_exit_nohz(void)
301{
302}
303#endif /* CONFIG_NO_HZ */
304
Paul E. McKenneya6826042009-02-25 18:03:42 -0800305/* A context switch is a grace period for rcutree. */
306static inline int rcu_blocking_is_gp(void)
307{
308 return num_online_cpus() == 1;
309}
310
Paul E. McKenney64db4cf2008-12-18 21:55:32 +0100311#endif /* __LINUX_RCUTREE_H */