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Source at commit ec7cab4cbb721bff91ec924ec691efd8daf36579 created 12 years 8 months ago. By Maarten ter Huurne, MIPS: JZ4740: A320: Updated quickstart documentation. | |
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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 did work well going from three levels to four. |
35 | * Of course, your mileage may vary. |
36 | */ |
37 | #define MAX_RCU_LVLS 4 |
38 | #if CONFIG_RCU_FANOUT > 16 |
39 | #define RCU_FANOUT_LEAF 16 |
40 | #else /* #if CONFIG_RCU_FANOUT > 16 */ |
41 | #define RCU_FANOUT_LEAF (CONFIG_RCU_FANOUT) |
42 | #endif /* #else #if CONFIG_RCU_FANOUT > 16 */ |
43 | #define RCU_FANOUT_1 (RCU_FANOUT_LEAF) |
44 | #define RCU_FANOUT_2 (RCU_FANOUT_1 * CONFIG_RCU_FANOUT) |
45 | #define RCU_FANOUT_3 (RCU_FANOUT_2 * CONFIG_RCU_FANOUT) |
46 | #define RCU_FANOUT_4 (RCU_FANOUT_3 * CONFIG_RCU_FANOUT) |
47 | |
48 | #if NR_CPUS <= RCU_FANOUT_1 |
49 | # define NUM_RCU_LVLS 1 |
50 | # define NUM_RCU_LVL_0 1 |
51 | # define NUM_RCU_LVL_1 (NR_CPUS) |
52 | # define NUM_RCU_LVL_2 0 |
53 | # define NUM_RCU_LVL_3 0 |
54 | # define NUM_RCU_LVL_4 0 |
55 | #elif NR_CPUS <= RCU_FANOUT_2 |
56 | # define NUM_RCU_LVLS 2 |
57 | # define NUM_RCU_LVL_0 1 |
58 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
59 | # define NUM_RCU_LVL_2 (NR_CPUS) |
60 | # define NUM_RCU_LVL_3 0 |
61 | # define NUM_RCU_LVL_4 0 |
62 | #elif NR_CPUS <= RCU_FANOUT_3 |
63 | # define NUM_RCU_LVLS 3 |
64 | # define NUM_RCU_LVL_0 1 |
65 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) |
66 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
67 | # define NUM_RCU_LVL_3 (NR_CPUS) |
68 | # define NUM_RCU_LVL_4 0 |
69 | #elif NR_CPUS <= RCU_FANOUT_4 |
70 | # define NUM_RCU_LVLS 4 |
71 | # define NUM_RCU_LVL_0 1 |
72 | # define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3) |
73 | # define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2) |
74 | # define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1) |
75 | # define NUM_RCU_LVL_4 (NR_CPUS) |
76 | #else |
77 | # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" |
78 | #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */ |
79 | |
80 | #define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4) |
81 | #define NUM_RCU_NODES (RCU_SUM - NR_CPUS) |
82 | |
83 | /* |
84 | * Dynticks per-CPU state. |
85 | */ |
86 | struct rcu_dynticks { |
87 | int dynticks_nesting; /* Track nesting level, sort of. */ |
88 | int dynticks; /* Even value for dynticks-idle, else odd. */ |
89 | int dynticks_nmi; /* Even value for either dynticks-idle or */ |
90 | /* not in nmi handler, else odd. So this */ |
91 | /* remains even for nmi from irq handler. */ |
92 | }; |
93 | |
94 | /* |
95 | * Definition for node within the RCU grace-period-detection hierarchy. |
96 | */ |
97 | struct rcu_node { |
98 | raw_spinlock_t lock; /* Root rcu_node's lock protects some */ |
99 | /* rcu_state fields as well as following. */ |
100 | unsigned long gpnum; /* Current grace period for this node. */ |
101 | /* This will either be equal to or one */ |
102 | /* behind the root rcu_node's gpnum. */ |
103 | unsigned long completed; /* Last GP completed for this node. */ |
104 | /* This will either be equal to or one */ |
105 | /* behind the root rcu_node's gpnum. */ |
106 | unsigned long qsmask; /* CPUs or groups that need to switch in */ |
107 | /* order for current grace period to proceed.*/ |
108 | /* In leaf rcu_node, each bit corresponds to */ |
109 | /* an rcu_data structure, otherwise, each */ |
110 | /* bit corresponds to a child rcu_node */ |
111 | /* structure. */ |
112 | unsigned long expmask; /* Groups that have ->blocked_tasks[] */ |
113 | /* elements that need to drain to allow the */ |
114 | /* current expedited grace period to */ |
115 | /* complete (only for TREE_PREEMPT_RCU). */ |
116 | unsigned long qsmaskinit; |
117 | /* Per-GP initial value for qsmask & expmask. */ |
118 | unsigned long grpmask; /* Mask to apply to parent qsmask. */ |
119 | /* Only one bit will be set in this mask. */ |
120 | int grplo; /* lowest-numbered CPU or group here. */ |
121 | int grphi; /* highest-numbered CPU or group here. */ |
122 | u8 grpnum; /* CPU/group number for next level up. */ |
123 | u8 level; /* root is at level 0. */ |
124 | struct rcu_node *parent; |
125 | struct list_head blocked_tasks[4]; |
126 | /* Tasks blocked in RCU read-side critsect. */ |
127 | /* Grace period number (->gpnum) x blocked */ |
128 | /* by tasks on the (x & 0x1) element of the */ |
129 | /* blocked_tasks[] array. */ |
130 | } ____cacheline_internodealigned_in_smp; |
131 | |
132 | /* |
133 | * Do a full breadth-first scan of the rcu_node structures for the |
134 | * specified rcu_state structure. |
135 | */ |
136 | #define rcu_for_each_node_breadth_first(rsp, rnp) \ |
137 | for ((rnp) = &(rsp)->node[0]; \ |
138 | (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) |
139 | |
140 | /* |
141 | * Do a breadth-first scan of the non-leaf rcu_node structures for the |
142 | * specified rcu_state structure. Note that if there is a singleton |
143 | * rcu_node tree with but one rcu_node structure, this loop is a no-op. |
144 | */ |
145 | #define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \ |
146 | for ((rnp) = &(rsp)->node[0]; \ |
147 | (rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++) |
148 | |
149 | /* |
150 | * Scan the leaves of the rcu_node hierarchy for the specified rcu_state |
151 | * structure. Note that if there is a singleton rcu_node tree with but |
152 | * one rcu_node structure, this loop -will- visit the rcu_node structure. |
153 | * It is still a leaf node, even if it is also the root node. |
154 | */ |
155 | #define rcu_for_each_leaf_node(rsp, rnp) \ |
156 | for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
157 | (rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++) |
158 | |
159 | /* Index values for nxttail array in struct rcu_data. */ |
160 | #define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ |
161 | #define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ |
162 | #define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ |
163 | #define RCU_NEXT_TAIL 3 |
164 | #define RCU_NEXT_SIZE 4 |
165 | |
166 | /* Per-CPU data for read-copy update. */ |
167 | struct rcu_data { |
168 | /* 1) quiescent-state and grace-period handling : */ |
169 | unsigned long completed; /* Track rsp->completed gp number */ |
170 | /* in order to detect GP end. */ |
171 | unsigned long gpnum; /* Highest gp number that this CPU */ |
172 | /* is aware of having started. */ |
173 | unsigned long passed_quiesc_completed; |
174 | /* Value of completed at time of qs. */ |
175 | bool passed_quiesc; /* User-mode/idle loop etc. */ |
176 | bool qs_pending; /* Core waits for quiesc state. */ |
177 | bool beenonline; /* CPU online at least once. */ |
178 | bool preemptable; /* Preemptable RCU? */ |
179 | struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ |
180 | unsigned long grpmask; /* Mask to apply to leaf qsmask. */ |
181 | |
182 | /* 2) batch handling */ |
183 | /* |
184 | * If nxtlist is not NULL, it is partitioned as follows. |
185 | * Any of the partitions might be empty, in which case the |
186 | * pointer to that partition will be equal to the pointer for |
187 | * the following partition. When the list is empty, all of |
188 | * the nxttail elements point to the ->nxtlist pointer itself, |
189 | * which in that case is NULL. |
190 | * |
191 | * [nxtlist, *nxttail[RCU_DONE_TAIL]): |
192 | * Entries that batch # <= ->completed |
193 | * The grace period for these entries has completed, and |
194 | * the other grace-period-completed entries may be moved |
195 | * here temporarily in rcu_process_callbacks(). |
196 | * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): |
197 | * Entries that batch # <= ->completed - 1: waiting for current GP |
198 | * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): |
199 | * Entries known to have arrived before current GP ended |
200 | * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]): |
201 | * Entries that might have arrived after current GP ended |
202 | * Note that the value of *nxttail[RCU_NEXT_TAIL] will |
203 | * always be NULL, as this is the end of the list. |
204 | */ |
205 | struct rcu_head *nxtlist; |
206 | struct rcu_head **nxttail[RCU_NEXT_SIZE]; |
207 | long qlen; /* # of queued callbacks */ |
208 | long qlen_last_fqs_check; |
209 | /* qlen at last check for QS forcing */ |
210 | unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */ |
211 | unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */ |
212 | unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */ |
213 | unsigned long n_force_qs_snap; |
214 | /* did other CPU force QS recently? */ |
215 | long blimit; /* Upper limit on a processed batch */ |
216 | |
217 | #ifdef CONFIG_NO_HZ |
218 | /* 3) dynticks interface. */ |
219 | struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ |
220 | int dynticks_snap; /* Per-GP tracking for dynticks. */ |
221 | int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ |
222 | #endif /* #ifdef CONFIG_NO_HZ */ |
223 | |
224 | /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ |
225 | #ifdef CONFIG_NO_HZ |
226 | unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ |
227 | #endif /* #ifdef CONFIG_NO_HZ */ |
228 | unsigned long offline_fqs; /* Kicked due to being offline. */ |
229 | unsigned long resched_ipi; /* Sent a resched IPI. */ |
230 | |
231 | /* 5) __rcu_pending() statistics. */ |
232 | unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */ |
233 | unsigned long n_rp_qs_pending; |
234 | unsigned long n_rp_report_qs; |
235 | unsigned long n_rp_cb_ready; |
236 | unsigned long n_rp_cpu_needs_gp; |
237 | unsigned long n_rp_gp_completed; |
238 | unsigned long n_rp_gp_started; |
239 | unsigned long n_rp_need_fqs; |
240 | unsigned long n_rp_need_nothing; |
241 | |
242 | int cpu; |
243 | }; |
244 | |
245 | /* Values for signaled field in struct rcu_state. */ |
246 | #define RCU_GP_IDLE 0 /* No grace period in progress. */ |
247 | #define RCU_GP_INIT 1 /* Grace period being initialized. */ |
248 | #define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */ |
249 | #define RCU_FORCE_QS 3 /* Need to force quiescent state. */ |
250 | #ifdef CONFIG_NO_HZ |
251 | #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK |
252 | #else /* #ifdef CONFIG_NO_HZ */ |
253 | #define RCU_SIGNAL_INIT RCU_FORCE_QS |
254 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
255 | |
256 | #define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ |
257 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
258 | |
259 | #ifdef CONFIG_PROVE_RCU |
260 | #define RCU_STALL_DELAY_DELTA (5 * HZ) |
261 | #else |
262 | #define RCU_STALL_DELAY_DELTA 0 |
263 | #endif |
264 | |
265 | #define RCU_SECONDS_TILL_STALL_CHECK (CONFIG_RCU_CPU_STALL_TIMEOUT * HZ + \ |
266 | RCU_STALL_DELAY_DELTA) |
267 | /* for rsp->jiffies_stall */ |
268 | #define RCU_SECONDS_TILL_STALL_RECHECK (3 * RCU_SECONDS_TILL_STALL_CHECK + 30) |
269 | /* for rsp->jiffies_stall */ |
270 | #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ |
271 | /* to take at least one */ |
272 | /* scheduling clock irq */ |
273 | /* before ratting on them. */ |
274 | |
275 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR_RUNNABLE |
276 | #define RCU_CPU_STALL_SUPPRESS_INIT 0 |
277 | #else |
278 | #define RCU_CPU_STALL_SUPPRESS_INIT 1 |
279 | #endif |
280 | |
281 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
282 | |
283 | /* |
284 | * RCU global state, including node hierarchy. This hierarchy is |
285 | * represented in "heap" form in a dense array. The root (first level) |
286 | * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second |
287 | * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), |
288 | * and the third level in ->node[m+1] and following (->node[m+1] referenced |
289 | * by ->level[2]). The number of levels is determined by the number of |
290 | * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" |
291 | * consisting of a single rcu_node. |
292 | */ |
293 | struct rcu_state { |
294 | struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ |
295 | struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ |
296 | u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ |
297 | u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ |
298 | struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */ |
299 | |
300 | /* The following fields are guarded by the root rcu_node's lock. */ |
301 | |
302 | u8 signaled ____cacheline_internodealigned_in_smp; |
303 | /* Force QS state. */ |
304 | u8 fqs_active; /* force_quiescent_state() */ |
305 | /* is running. */ |
306 | u8 fqs_need_gp; /* A CPU was prevented from */ |
307 | /* starting a new grace */ |
308 | /* period because */ |
309 | /* force_quiescent_state() */ |
310 | /* was running. */ |
311 | unsigned long gpnum; /* Current gp number. */ |
312 | unsigned long completed; /* # of last completed gp. */ |
313 | |
314 | /* End of fields guarded by root rcu_node's lock. */ |
315 | |
316 | raw_spinlock_t onofflock; /* exclude on/offline and */ |
317 | /* starting new GP. */ |
318 | raw_spinlock_t fqslock; /* Only one task forcing */ |
319 | /* quiescent states. */ |
320 | unsigned long jiffies_force_qs; /* Time at which to invoke */ |
321 | /* force_quiescent_state(). */ |
322 | unsigned long n_force_qs; /* Number of calls to */ |
323 | /* force_quiescent_state(). */ |
324 | unsigned long n_force_qs_lh; /* ~Number of calls leaving */ |
325 | /* due to lock unavailable. */ |
326 | unsigned long n_force_qs_ngp; /* Number of calls leaving */ |
327 | /* due to no GP active. */ |
328 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
329 | unsigned long gp_start; /* Time at which GP started, */ |
330 | /* but in jiffies. */ |
331 | unsigned long jiffies_stall; /* Time at which to check */ |
332 | /* for CPU stalls. */ |
333 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
334 | char *name; /* Name of structure. */ |
335 | }; |
336 | |
337 | /* Return values for rcu_preempt_offline_tasks(). */ |
338 | |
339 | #define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */ |
340 | /* GP were moved to root. */ |
341 | #define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */ |
342 | /* GP were moved to root. */ |
343 | |
344 | /* |
345 | * RCU implementation internal declarations: |
346 | */ |
347 | extern struct rcu_state rcu_sched_state; |
348 | DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); |
349 | |
350 | extern struct rcu_state rcu_bh_state; |
351 | DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); |
352 | |
353 | #ifdef CONFIG_TREE_PREEMPT_RCU |
354 | extern struct rcu_state rcu_preempt_state; |
355 | DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); |
356 | #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ |
357 | |
358 | #ifndef RCU_TREE_NONCORE |
359 | |
360 | /* Forward declarations for rcutree_plugin.h */ |
361 | static void rcu_bootup_announce(void); |
362 | long rcu_batches_completed(void); |
363 | static void rcu_preempt_note_context_switch(int cpu); |
364 | static int rcu_preempted_readers(struct rcu_node *rnp); |
365 | #ifdef CONFIG_HOTPLUG_CPU |
366 | static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, |
367 | unsigned long flags); |
368 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
369 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
370 | static void rcu_print_detail_task_stall(struct rcu_state *rsp); |
371 | static void rcu_print_task_stall(struct rcu_node *rnp); |
372 | static void rcu_preempt_stall_reset(void); |
373 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
374 | static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); |
375 | #ifdef CONFIG_HOTPLUG_CPU |
376 | static int rcu_preempt_offline_tasks(struct rcu_state *rsp, |
377 | struct rcu_node *rnp, |
378 | struct rcu_data *rdp); |
379 | static void rcu_preempt_offline_cpu(int cpu); |
380 | #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |
381 | static void rcu_preempt_check_callbacks(int cpu); |
382 | static void rcu_preempt_process_callbacks(void); |
383 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); |
384 | #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) |
385 | static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp); |
386 | #endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */ |
387 | static int rcu_preempt_pending(int cpu); |
388 | static int rcu_preempt_needs_cpu(int cpu); |
389 | static void __cpuinit rcu_preempt_init_percpu_data(int cpu); |
390 | static void rcu_preempt_send_cbs_to_online(void); |
391 | static void __init __rcu_init_preempt(void); |
392 | static void rcu_needs_cpu_flush(void); |
393 | |
394 | #endif /* #ifndef RCU_TREE_NONCORE */ |
395 |
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