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9f77da9f PM |
1 | /* |
2 | * Read-Copy Update mechanism for mutual exclusion (tree-based version) | |
3 | * Internal non-public definitions. | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License as published by | |
7 | * the Free Software Foundation; either version 2 of the License, or | |
8 | * (at your option) any later version. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program; if not, write to the Free Software | |
17 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
18 | * | |
19 | * Copyright IBM Corporation, 2008 | |
20 | * | |
21 | * Author: Ingo Molnar <mingo@elte.hu> | |
22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
23 | */ | |
24 | ||
25 | #include <linux/cache.h> | |
26 | #include <linux/spinlock.h> | |
27 | #include <linux/threads.h> | |
28 | #include <linux/cpumask.h> | |
29 | #include <linux/seqlock.h> | |
30 | ||
31 | /* | |
32 | * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT. | |
33 | * In theory, it should be possible to add more levels straightforwardly. | |
34 | * In practice, this has not been tested, so there is probably some | |
35 | * bug somewhere. | |
36 | */ | |
37 | #define MAX_RCU_LVLS 3 | |
38 | #define RCU_FANOUT (CONFIG_RCU_FANOUT) | |
39 | #define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) | |
40 | #define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT) | |
41 | ||
42 | #if NR_CPUS <= RCU_FANOUT | |
43 | # define NUM_RCU_LVLS 1 | |
44 | # define NUM_RCU_LVL_0 1 | |
45 | # define NUM_RCU_LVL_1 (NR_CPUS) | |
46 | # define NUM_RCU_LVL_2 0 | |
47 | # define NUM_RCU_LVL_3 0 | |
48 | #elif NR_CPUS <= RCU_FANOUT_SQ | |
49 | # define NUM_RCU_LVLS 2 | |
50 | # define NUM_RCU_LVL_0 1 | |
fc2219d4 | 51 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) |
9f77da9f PM |
52 | # define NUM_RCU_LVL_2 (NR_CPUS) |
53 | # define NUM_RCU_LVL_3 0 | |
54 | #elif NR_CPUS <= RCU_FANOUT_CUBE | |
55 | # define NUM_RCU_LVLS 3 | |
56 | # define NUM_RCU_LVL_0 1 | |
fc2219d4 PM |
57 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ) |
58 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT) | |
9f77da9f PM |
59 | # define NUM_RCU_LVL_3 NR_CPUS |
60 | #else | |
61 | # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" | |
62 | #endif /* #if (NR_CPUS) <= RCU_FANOUT */ | |
63 | ||
64 | #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) | |
65 | #define NUM_RCU_NODES (RCU_SUM - NR_CPUS) | |
66 | ||
67 | /* | |
68 | * Dynticks per-CPU state. | |
69 | */ | |
70 | struct rcu_dynticks { | |
71 | int dynticks_nesting; /* Track nesting level, sort of. */ | |
72 | int dynticks; /* Even value for dynticks-idle, else odd. */ | |
73 | int dynticks_nmi; /* Even value for either dynticks-idle or */ | |
74 | /* not in nmi handler, else odd. So this */ | |
75 | /* remains even for nmi from irq handler. */ | |
76 | }; | |
77 | ||
78 | /* | |
79 | * Definition for node within the RCU grace-period-detection hierarchy. | |
80 | */ | |
81 | struct rcu_node { | |
1eba8f84 PM |
82 | spinlock_t lock; /* Root rcu_node's lock protects some */ |
83 | /* rcu_state fields as well as following. */ | |
f41d911f | 84 | long gpnum; /* Current grace period for this node. */ |
86848966 PM |
85 | /* This will either be equal to or one */ |
86 | /* behind the root rcu_node's gpnum. */ | |
d09b62df PM |
87 | long completed; /* Last grace period completed for this node. */ |
88 | /* This will either be equal to or one */ | |
89 | /* behind the root rcu_node's gpnum. */ | |
9f77da9f PM |
90 | unsigned long qsmask; /* CPUs or groups that need to switch in */ |
91 | /* order for current grace period to proceed.*/ | |
1eba8f84 PM |
92 | /* In leaf rcu_node, each bit corresponds to */ |
93 | /* an rcu_data structure, otherwise, each */ | |
94 | /* bit corresponds to a child rcu_node */ | |
95 | /* structure. */ | |
9f77da9f PM |
96 | unsigned long qsmaskinit; |
97 | /* Per-GP initialization for qsmask. */ | |
98 | unsigned long grpmask; /* Mask to apply to parent qsmask. */ | |
1eba8f84 | 99 | /* Only one bit will be set in this mask. */ |
9f77da9f PM |
100 | int grplo; /* lowest-numbered CPU or group here. */ |
101 | int grphi; /* highest-numbered CPU or group here. */ | |
102 | u8 grpnum; /* CPU/group number for next level up. */ | |
103 | u8 level; /* root is at level 0. */ | |
104 | struct rcu_node *parent; | |
f41d911f PM |
105 | struct list_head blocked_tasks[2]; |
106 | /* Tasks blocked in RCU read-side critsect. */ | |
1eba8f84 PM |
107 | /* Grace period number (->gpnum) x blocked */ |
108 | /* by tasks on the (x & 0x1) element of the */ | |
109 | /* blocked_tasks[] array. */ | |
9f77da9f PM |
110 | } ____cacheline_internodealigned_in_smp; |
111 | ||
a0b6c9a7 PM |
112 | /* |
113 | * Do a full breadth-first scan of the rcu_node structures for the | |
114 | * specified rcu_state structure. | |
115 | */ | |
116 | #define rcu_for_each_node_breadth_first(rsp, rnp) \ | |
117 | for ((rnp) = &(rsp)->node[0]; \ | |
118 | (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) | |
119 | ||
120 | #define rcu_for_each_leaf_node(rsp, rnp) \ | |
121 | for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \ | |
122 | (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) | |
123 | ||
9f77da9f PM |
124 | /* Index values for nxttail array in struct rcu_data. */ |
125 | #define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ | |
126 | #define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ | |
127 | #define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ | |
128 | #define RCU_NEXT_TAIL 3 | |
129 | #define RCU_NEXT_SIZE 4 | |
130 | ||
131 | /* Per-CPU data for read-copy update. */ | |
132 | struct rcu_data { | |
133 | /* 1) quiescent-state and grace-period handling : */ | |
134 | long completed; /* Track rsp->completed gp number */ | |
135 | /* in order to detect GP end. */ | |
136 | long gpnum; /* Highest gp number that this CPU */ | |
137 | /* is aware of having started. */ | |
138 | long passed_quiesc_completed; | |
139 | /* Value of completed at time of qs. */ | |
140 | bool passed_quiesc; /* User-mode/idle loop etc. */ | |
141 | bool qs_pending; /* Core waits for quiesc state. */ | |
142 | bool beenonline; /* CPU online at least once. */ | |
f41d911f | 143 | bool preemptable; /* Preemptable RCU? */ |
9f77da9f PM |
144 | struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ |
145 | unsigned long grpmask; /* Mask to apply to leaf qsmask. */ | |
146 | ||
147 | /* 2) batch handling */ | |
148 | /* | |
149 | * If nxtlist is not NULL, it is partitioned as follows. | |
150 | * Any of the partitions might be empty, in which case the | |
151 | * pointer to that partition will be equal to the pointer for | |
152 | * the following partition. When the list is empty, all of | |
1eba8f84 PM |
153 | * the nxttail elements point to the ->nxtlist pointer itself, |
154 | * which in that case is NULL. | |
9f77da9f | 155 | * |
9f77da9f PM |
156 | * [nxtlist, *nxttail[RCU_DONE_TAIL]): |
157 | * Entries that batch # <= ->completed | |
158 | * The grace period for these entries has completed, and | |
159 | * the other grace-period-completed entries may be moved | |
160 | * here temporarily in rcu_process_callbacks(). | |
1eba8f84 PM |
161 | * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): |
162 | * Entries that batch # <= ->completed - 1: waiting for current GP | |
163 | * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): | |
164 | * Entries known to have arrived before current GP ended | |
165 | * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]): | |
166 | * Entries that might have arrived after current GP ended | |
167 | * Note that the value of *nxttail[RCU_NEXT_TAIL] will | |
168 | * always be NULL, as this is the end of the list. | |
9f77da9f PM |
169 | */ |
170 | struct rcu_head *nxtlist; | |
171 | struct rcu_head **nxttail[RCU_NEXT_SIZE]; | |
a71fca58 | 172 | long qlen; /* # of queued callbacks */ |
37c72e56 PM |
173 | long qlen_last_fqs_check; |
174 | /* qlen at last check for QS forcing */ | |
175 | unsigned long n_force_qs_snap; | |
176 | /* did other CPU force QS recently? */ | |
9f77da9f PM |
177 | long blimit; /* Upper limit on a processed batch */ |
178 | ||
179 | #ifdef CONFIG_NO_HZ | |
180 | /* 3) dynticks interface. */ | |
181 | struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ | |
182 | int dynticks_snap; /* Per-GP tracking for dynticks. */ | |
183 | int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ | |
184 | #endif /* #ifdef CONFIG_NO_HZ */ | |
185 | ||
186 | /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ | |
187 | #ifdef CONFIG_NO_HZ | |
188 | unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ | |
189 | #endif /* #ifdef CONFIG_NO_HZ */ | |
190 | unsigned long offline_fqs; /* Kicked due to being offline. */ | |
191 | unsigned long resched_ipi; /* Sent a resched IPI. */ | |
192 | ||
193 | /* 5) __rcu_pending() statistics. */ | |
194 | long n_rcu_pending; /* rcu_pending() calls since boot. */ | |
195 | long n_rp_qs_pending; | |
196 | long n_rp_cb_ready; | |
197 | long n_rp_cpu_needs_gp; | |
198 | long n_rp_gp_completed; | |
199 | long n_rp_gp_started; | |
200 | long n_rp_need_fqs; | |
201 | long n_rp_need_nothing; | |
202 | ||
203 | int cpu; | |
204 | }; | |
205 | ||
206 | /* Values for signaled field in struct rcu_state. */ | |
83f5b01f PM |
207 | #define RCU_GP_IDLE 0 /* No grace period in progress. */ |
208 | #define RCU_GP_INIT 1 /* Grace period being initialized. */ | |
209 | #define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */ | |
281d150c PM |
210 | #define RCU_SAVE_COMPLETED 3 /* Need to save rsp->completed. */ |
211 | #define RCU_FORCE_QS 4 /* Need to force quiescent state. */ | |
9f77da9f PM |
212 | #ifdef CONFIG_NO_HZ |
213 | #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK | |
214 | #else /* #ifdef CONFIG_NO_HZ */ | |
281d150c | 215 | #define RCU_SIGNAL_INIT RCU_SAVE_COMPLETED |
9f77da9f PM |
216 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
217 | ||
218 | #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ | |
219 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
220 | #define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ | |
221 | #define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */ | |
222 | #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ | |
223 | /* to take at least one */ | |
224 | /* scheduling clock irq */ | |
225 | /* before ratting on them. */ | |
226 | ||
227 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
228 | ||
229 | /* | |
230 | * RCU global state, including node hierarchy. This hierarchy is | |
231 | * represented in "heap" form in a dense array. The root (first level) | |
232 | * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second | |
233 | * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), | |
234 | * and the third level in ->node[m+1] and following (->node[m+1] referenced | |
235 | * by ->level[2]). The number of levels is determined by the number of | |
236 | * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" | |
237 | * consisting of a single rcu_node. | |
238 | */ | |
239 | struct rcu_state { | |
240 | struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ | |
241 | struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ | |
242 | u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ | |
243 | u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ | |
244 | struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */ | |
245 | ||
246 | /* The following fields are guarded by the root rcu_node's lock. */ | |
247 | ||
248 | u8 signaled ____cacheline_internodealigned_in_smp; | |
249 | /* Force QS state. */ | |
250 | long gpnum; /* Current gp number. */ | |
251 | long completed; /* # of last completed gp. */ | |
1eba8f84 PM |
252 | |
253 | /* End of fields guarded by root rcu_node's lock. */ | |
254 | ||
9f77da9f | 255 | spinlock_t onofflock; /* exclude on/offline and */ |
e74f4c45 PM |
256 | /* starting new GP. Also */ |
257 | /* protects the following */ | |
258 | /* orphan_cbs fields. */ | |
259 | struct rcu_head *orphan_cbs_list; /* list of rcu_head structs */ | |
260 | /* orphaned by all CPUs in */ | |
261 | /* a given leaf rcu_node */ | |
262 | /* going offline. */ | |
263 | struct rcu_head **orphan_cbs_tail; /* And tail pointer. */ | |
264 | long orphan_qlen; /* Number of orphaned cbs. */ | |
9f77da9f PM |
265 | spinlock_t fqslock; /* Only one task forcing */ |
266 | /* quiescent states. */ | |
4bcfe055 PM |
267 | long completed_fqs; /* Value of completed @ snap. */ |
268 | /* Protected by fqslock. */ | |
9f77da9f PM |
269 | unsigned long jiffies_force_qs; /* Time at which to invoke */ |
270 | /* force_quiescent_state(). */ | |
271 | unsigned long n_force_qs; /* Number of calls to */ | |
272 | /* force_quiescent_state(). */ | |
273 | unsigned long n_force_qs_lh; /* ~Number of calls leaving */ | |
274 | /* due to lock unavailable. */ | |
275 | unsigned long n_force_qs_ngp; /* Number of calls leaving */ | |
276 | /* due to no GP active. */ | |
277 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
278 | unsigned long gp_start; /* Time at which GP started, */ | |
279 | /* but in jiffies. */ | |
280 | unsigned long jiffies_stall; /* Time at which to check */ | |
281 | /* for CPU stalls. */ | |
282 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
9f77da9f PM |
283 | }; |
284 | ||
285 | #ifdef RCU_TREE_NONCORE | |
6258c4fb IM |
286 | |
287 | /* | |
288 | * RCU implementation internal declarations: | |
289 | */ | |
d6714c22 PM |
290 | extern struct rcu_state rcu_sched_state; |
291 | DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); | |
6258c4fb IM |
292 | |
293 | extern struct rcu_state rcu_bh_state; | |
294 | DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); | |
295 | ||
f41d911f PM |
296 | #ifdef CONFIG_TREE_PREEMPT_RCU |
297 | extern struct rcu_state rcu_preempt_state; | |
298 | DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); | |
299 | #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ | |
300 | ||
9b2619af | 301 | #else /* #ifdef RCU_TREE_NONCORE */ |
9f77da9f | 302 | |
9b2619af | 303 | /* Forward declarations for rcutree_plugin.h */ |
dbe01350 | 304 | static void rcu_bootup_announce(void); |
9b2619af PM |
305 | long rcu_batches_completed(void); |
306 | static void rcu_preempt_note_context_switch(int cpu); | |
307 | static int rcu_preempted_readers(struct rcu_node *rnp); | |
308 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR | |
309 | static void rcu_print_task_stall(struct rcu_node *rnp); | |
310 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ | |
311 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); | |
312 | #ifdef CONFIG_HOTPLUG_CPU | |
237c80c5 PM |
313 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
314 | struct rcu_node *rnp, | |
315 | struct rcu_data *rdp); | |
9b2619af PM |
316 | static void rcu_preempt_offline_cpu(int cpu); |
317 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ | |
318 | static void rcu_preempt_check_callbacks(int cpu); | |
319 | static void rcu_preempt_process_callbacks(void); | |
320 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); | |
321 | static int rcu_preempt_pending(int cpu); | |
322 | static int rcu_preempt_needs_cpu(int cpu); | |
323 | static void __cpuinit rcu_preempt_init_percpu_data(int cpu); | |
e74f4c45 | 324 | static void rcu_preempt_send_cbs_to_orphanage(void); |
9b2619af PM |
325 | static void __init __rcu_init_preempt(void); |
326 | ||
327 | #endif /* #else #ifdef RCU_TREE_NONCORE */ |