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64db4cff PM |
1 | /* |
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> | |
64db4cff PM |
36 | #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 | */ | |
78 | struct 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 | */ | |
89 | struct 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. */ | |
111 | struct 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 | ||
164 | /* 5) state to allow this CPU to force_quiescent_state on others */ | |
165 | long n_rcu_pending; /* rcu_pending() calls since boot. */ | |
166 | long n_rcu_pending_force_qs; /* when to force quiescent states. */ | |
167 | ||
168 | int cpu; | |
169 | }; | |
170 | ||
171 | /* Values for signaled field in struct rcu_state. */ | |
172 | #define RCU_GP_INIT 0 /* Grace period being initialized. */ | |
173 | #define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */ | |
174 | #define RCU_FORCE_QS 2 /* Need to force quiescent state. */ | |
175 | #ifdef CONFIG_NO_HZ | |
176 | #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK | |
177 | #else /* #ifdef CONFIG_NO_HZ */ | |
178 | #define RCU_SIGNAL_INIT RCU_FORCE_QS | |
179 | #endif /* #else #ifdef CONFIG_NO_HZ */ | |
180 | ||
181 | #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ | |
182 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
183 | #define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ | |
184 | #define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */ | |
185 | #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ | |
186 | /* to take at least one */ | |
187 | /* scheduling clock irq */ | |
188 | /* before ratting on them. */ | |
189 | ||
190 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
191 | ||
192 | /* | |
193 | * RCU global state, including node hierarchy. This hierarchy is | |
194 | * represented in "heap" form in a dense array. The root (first level) | |
195 | * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second | |
196 | * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), | |
197 | * and the third level in ->node[m+1] and following (->node[m+1] referenced | |
198 | * by ->level[2]). The number of levels is determined by the number of | |
199 | * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" | |
200 | * consisting of a single rcu_node. | |
201 | */ | |
202 | struct rcu_state { | |
203 | struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ | |
204 | struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ | |
205 | u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ | |
206 | u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ | |
207 | struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */ | |
208 | ||
209 | /* The following fields are guarded by the root rcu_node's lock. */ | |
210 | ||
211 | u8 signaled ____cacheline_internodealigned_in_smp; | |
212 | /* Force QS state. */ | |
213 | long gpnum; /* Current gp number. */ | |
214 | long completed; /* # of last completed gp. */ | |
215 | spinlock_t onofflock; /* exclude on/offline and */ | |
216 | /* starting new GP. */ | |
217 | spinlock_t fqslock; /* Only one task forcing */ | |
218 | /* quiescent states. */ | |
219 | unsigned long jiffies_force_qs; /* Time at which to invoke */ | |
220 | /* force_quiescent_state(). */ | |
221 | unsigned long n_force_qs; /* Number of calls to */ | |
222 | /* force_quiescent_state(). */ | |
223 | unsigned long n_force_qs_lh; /* ~Number of calls leaving */ | |
224 | /* due to lock unavailable. */ | |
225 | unsigned long n_force_qs_ngp; /* Number of calls leaving */ | |
226 | /* due to no GP active. */ | |
227 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
228 | unsigned long gp_start; /* Time at which GP started, */ | |
229 | /* but in jiffies. */ | |
230 | unsigned long jiffies_stall; /* Time at which to check */ | |
231 | /* for CPU stalls. */ | |
232 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
233 | #ifdef CONFIG_NO_HZ | |
234 | long dynticks_completed; /* Value of completed @ snap. */ | |
235 | #endif /* #ifdef CONFIG_NO_HZ */ | |
236 | }; | |
237 | ||
b1f77b05 IM |
238 | extern void rcu_qsctr_inc(int cpu); |
239 | extern void rcu_bh_qsctr_inc(int cpu); | |
64db4cff PM |
240 | |
241 | extern int rcu_pending(int cpu); | |
242 | extern int rcu_needs_cpu(int cpu); | |
243 | ||
244 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
245 | extern struct lockdep_map rcu_lock_map; | |
246 | # define rcu_read_acquire() \ | |
247 | lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) | |
248 | # define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) | |
249 | #else | |
250 | # define rcu_read_acquire() do { } while (0) | |
251 | # define rcu_read_release() do { } while (0) | |
252 | #endif | |
253 | ||
254 | static inline void __rcu_read_lock(void) | |
255 | { | |
256 | preempt_disable(); | |
257 | __acquire(RCU); | |
258 | rcu_read_acquire(); | |
259 | } | |
260 | static inline void __rcu_read_unlock(void) | |
261 | { | |
262 | rcu_read_release(); | |
263 | __release(RCU); | |
264 | preempt_enable(); | |
265 | } | |
266 | static inline void __rcu_read_lock_bh(void) | |
267 | { | |
268 | local_bh_disable(); | |
269 | __acquire(RCU_BH); | |
270 | rcu_read_acquire(); | |
271 | } | |
272 | static inline void __rcu_read_unlock_bh(void) | |
273 | { | |
274 | rcu_read_release(); | |
275 | __release(RCU_BH); | |
276 | local_bh_enable(); | |
277 | } | |
278 | ||
279 | #define __synchronize_sched() synchronize_rcu() | |
280 | ||
281 | #define call_rcu_sched(head, func) call_rcu(head, func) | |
282 | ||
283 | static inline void rcu_init_sched(void) | |
284 | { | |
285 | } | |
286 | ||
287 | extern void __rcu_init(void); | |
288 | extern void rcu_check_callbacks(int cpu, int user); | |
289 | extern void rcu_restart_cpu(int cpu); | |
290 | ||
291 | extern long rcu_batches_completed(void); | |
292 | extern long rcu_batches_completed_bh(void); | |
293 | ||
294 | #ifdef CONFIG_NO_HZ | |
295 | void rcu_enter_nohz(void); | |
296 | void rcu_exit_nohz(void); | |
297 | #else /* CONFIG_NO_HZ */ | |
298 | static inline void rcu_enter_nohz(void) | |
299 | { | |
300 | } | |
301 | static inline void rcu_exit_nohz(void) | |
302 | { | |
303 | } | |
304 | #endif /* CONFIG_NO_HZ */ | |
305 | ||
a6826048 PM |
306 | /* A context switch is a grace period for rcutree. */ |
307 | static inline int rcu_blocking_is_gp(void) | |
308 | { | |
309 | return num_online_cpus() == 1; | |
310 | } | |
311 | ||
64db4cff | 312 | #endif /* __LINUX_RCUTREE_H */ |