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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, you can access it online at
17 * http://www.gnu.org/licenses/gpl-2.0.html.
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#include <linux/swait.h>
31#include <linux/stop_machine.h>
32
33/*
34 * Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
35 * CONFIG_RCU_FANOUT_LEAF.
36 * In theory, it should be possible to add more levels straightforwardly.
37 * In practice, this did work well going from three levels to four.
38 * Of course, your mileage may vary.
39 */
40
41#ifdef CONFIG_RCU_FANOUT
42#define RCU_FANOUT CONFIG_RCU_FANOUT
43#else /* #ifdef CONFIG_RCU_FANOUT */
44# ifdef CONFIG_64BIT
45# define RCU_FANOUT 64
46# else
47# define RCU_FANOUT 32
48# endif
49#endif /* #else #ifdef CONFIG_RCU_FANOUT */
50
51#ifdef CONFIG_RCU_FANOUT_LEAF
52#define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF
53#else /* #ifdef CONFIG_RCU_FANOUT_LEAF */
54# ifdef CONFIG_64BIT
55# define RCU_FANOUT_LEAF 64
56# else
57# define RCU_FANOUT_LEAF 32
58# endif
59#endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */
60
61#define RCU_FANOUT_1 (RCU_FANOUT_LEAF)
62#define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT)
63#define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT)
64#define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT)
65
66#if NR_CPUS <= RCU_FANOUT_1
67# define RCU_NUM_LVLS 1
68# define NUM_RCU_LVL_0 1
69# define NUM_RCU_NODES NUM_RCU_LVL_0
70# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 }
71# define RCU_NODE_NAME_INIT { "rcu_node_0" }
72# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
73# define RCU_EXP_NAME_INIT { "rcu_node_exp_0" }
74#elif NR_CPUS <= RCU_FANOUT_2
75# define RCU_NUM_LVLS 2
76# define NUM_RCU_LVL_0 1
77# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
78# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1)
79# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 }
80# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
81# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
82# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" }
83#elif NR_CPUS <= RCU_FANOUT_3
84# define RCU_NUM_LVLS 3
85# define NUM_RCU_LVL_0 1
86# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
87# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
88# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2)
89# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 }
90# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
91# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
92# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" }
93#elif NR_CPUS <= RCU_FANOUT_4
94# define RCU_NUM_LVLS 4
95# define NUM_RCU_LVL_0 1
96# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
97# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
98# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
99# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
100# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 }
101# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
102# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
103# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" }
104#else
105# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
106#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
107
108extern int rcu_num_lvls;
109extern int rcu_num_nodes;
110
111/*
112 * Dynticks per-CPU state.
113 */
114struct rcu_dynticks {
115 long long dynticks_nesting; /* Track irq/process nesting level. */
116 /* Process level is worth LLONG_MAX/2. */
117 int dynticks_nmi_nesting; /* Track NMI nesting level. */
118 atomic_t dynticks; /* Even value for idle, else odd. */
119#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
120 long long dynticks_idle_nesting;
121 /* irq/process nesting level from idle. */
122 atomic_t dynticks_idle; /* Even value for idle, else odd. */
123 /* "Idle" excludes userspace execution. */
124 unsigned long dynticks_idle_jiffies;
125 /* End of last non-NMI non-idle period. */
126#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
127#ifdef CONFIG_RCU_FAST_NO_HZ
128 bool all_lazy; /* Are all CPU's CBs lazy? */
129 unsigned long nonlazy_posted;
130 /* # times non-lazy CBs posted to CPU. */
131 unsigned long nonlazy_posted_snap;
132 /* idle-period nonlazy_posted snapshot. */
133 unsigned long last_accelerate;
134 /* Last jiffy CBs were accelerated. */
135 unsigned long last_advance_all;
136 /* Last jiffy CBs were all advanced. */
137 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
138#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
139};
140
141/* RCU's kthread states for tracing. */
142#define RCU_KTHREAD_STOPPED 0
143#define RCU_KTHREAD_RUNNING 1
144#define RCU_KTHREAD_WAITING 2
145#define RCU_KTHREAD_OFFCPU 3
146#define RCU_KTHREAD_YIELDING 4
147#define RCU_KTHREAD_MAX 4
148
149/*
150 * Definition for node within the RCU grace-period-detection hierarchy.
151 */
152struct rcu_node {
153 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
154 /* some rcu_state fields as well as */
155 /* following. */
156 unsigned long gpnum; /* Current grace period for this node. */
157 /* This will either be equal to or one */
158 /* behind the root rcu_node's gpnum. */
159 unsigned long completed; /* Last GP completed for this node. */
160 /* This will either be equal to or one */
161 /* behind the root rcu_node's gpnum. */
162 unsigned long qsmask; /* CPUs or groups that need to switch in */
163 /* order for current grace period to proceed.*/
164 /* In leaf rcu_node, each bit corresponds to */
165 /* an rcu_data structure, otherwise, each */
166 /* bit corresponds to a child rcu_node */
167 /* structure. */
168 unsigned long qsmaskinit;
169 /* Per-GP initial value for qsmask. */
170 /* Initialized from ->qsmaskinitnext at the */
171 /* beginning of each grace period. */
172 unsigned long qsmaskinitnext;
173 /* Online CPUs for next grace period. */
174 unsigned long expmask; /* CPUs or groups that need to check in */
175 /* to allow the current expedited GP */
176 /* to complete. */
177 unsigned long expmaskinit;
178 /* Per-GP initial values for expmask. */
179 /* Initialized from ->expmaskinitnext at the */
180 /* beginning of each expedited GP. */
181 unsigned long expmaskinitnext;
182 /* Online CPUs for next expedited GP. */
183 /* Any CPU that has ever been online will */
184 /* have its bit set. */
185 unsigned long grpmask; /* Mask to apply to parent qsmask. */
186 /* Only one bit will be set in this mask. */
187 int grplo; /* lowest-numbered CPU or group here. */
188 int grphi; /* highest-numbered CPU or group here. */
189 u8 grpnum; /* CPU/group number for next level up. */
190 u8 level; /* root is at level 0. */
191 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
192 /* exit RCU read-side critical sections */
193 /* before propagating offline up the */
194 /* rcu_node tree? */
195 struct rcu_node *parent;
196 struct list_head blkd_tasks;
197 /* Tasks blocked in RCU read-side critical */
198 /* section. Tasks are placed at the head */
199 /* of this list and age towards the tail. */
200 struct list_head *gp_tasks;
201 /* Pointer to the first task blocking the */
202 /* current grace period, or NULL if there */
203 /* is no such task. */
204 struct list_head *exp_tasks;
205 /* Pointer to the first task blocking the */
206 /* current expedited grace period, or NULL */
207 /* if there is no such task. If there */
208 /* is no current expedited grace period, */
209 /* then there can cannot be any such task. */
210 struct list_head *boost_tasks;
211 /* Pointer to first task that needs to be */
212 /* priority boosted, or NULL if no priority */
213 /* boosting is needed for this rcu_node */
214 /* structure. If there are no tasks */
215 /* queued on this rcu_node structure that */
216 /* are blocking the current grace period, */
217 /* there can be no such task. */
218 struct rt_mutex boost_mtx;
219 /* Used only for the priority-boosting */
220 /* side effect, not as a lock. */
221 unsigned long boost_time;
222 /* When to start boosting (jiffies). */
223 struct task_struct *boost_kthread_task;
224 /* kthread that takes care of priority */
225 /* boosting for this rcu_node structure. */
226 unsigned int boost_kthread_status;
227 /* State of boost_kthread_task for tracing. */
228 unsigned long n_tasks_boosted;
229 /* Total number of tasks boosted. */
230 unsigned long n_exp_boosts;
231 /* Number of tasks boosted for expedited GP. */
232 unsigned long n_normal_boosts;
233 /* Number of tasks boosted for normal GP. */
234 unsigned long n_balk_blkd_tasks;
235 /* Refused to boost: no blocked tasks. */
236 unsigned long n_balk_exp_gp_tasks;
237 /* Refused to boost: nothing blocking GP. */
238 unsigned long n_balk_boost_tasks;
239 /* Refused to boost: already boosting. */
240 unsigned long n_balk_notblocked;
241 /* Refused to boost: RCU RS CS still running. */
242 unsigned long n_balk_notyet;
243 /* Refused to boost: not yet time. */
244 unsigned long n_balk_nos;
245 /* Refused to boost: not sure why, though. */
246 /* This can happen due to race conditions. */
247#ifdef CONFIG_RCU_NOCB_CPU
248 struct swait_queue_head nocb_gp_wq[2];
249 /* Place for rcu_nocb_kthread() to wait GP. */
250#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
251 int need_future_gp[2];
252 /* Counts of upcoming no-CB GP requests. */
253 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
254
255 struct mutex exp_funnel_mutex ____cacheline_internodealigned_in_smp;
256} ____cacheline_internodealigned_in_smp;
257
258/*
259 * Do a full breadth-first scan of the rcu_node structures for the
260 * specified rcu_state structure.
261 */
262#define rcu_for_each_node_breadth_first(rsp, rnp) \
263 for ((rnp) = &(rsp)->node[0]; \
264 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
265
266/*
267 * Do a breadth-first scan of the non-leaf rcu_node structures for the
268 * specified rcu_state structure. Note that if there is a singleton
269 * rcu_node tree with but one rcu_node structure, this loop is a no-op.
270 */
271#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
272 for ((rnp) = &(rsp)->node[0]; \
273 (rnp) < (rsp)->level[rcu_num_lvls - 1]; (rnp)++)
274
275/*
276 * Scan the leaves of the rcu_node hierarchy for the specified rcu_state
277 * structure. Note that if there is a singleton rcu_node tree with but
278 * one rcu_node structure, this loop -will- visit the rcu_node structure.
279 * It is still a leaf node, even if it is also the root node.
280 */
281#define rcu_for_each_leaf_node(rsp, rnp) \
282 for ((rnp) = (rsp)->level[rcu_num_lvls - 1]; \
283 (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++)
284
285/*
286 * Union to allow "aggregate OR" operation on the need for a quiescent
287 * state by the normal and expedited grace periods.
288 */
289union rcu_noqs {
290 struct {
291 u8 norm;
292 u8 exp;
293 } b; /* Bits. */
294 u16 s; /* Set of bits, aggregate OR here. */
295};
296
297/* Index values for nxttail array in struct rcu_data. */
298#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
299#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
300#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
301#define RCU_NEXT_TAIL 3
302#define RCU_NEXT_SIZE 4
303
304/* Per-CPU data for read-copy update. */
305struct rcu_data {
306 /* 1) quiescent-state and grace-period handling : */
307 unsigned long completed; /* Track rsp->completed gp number */
308 /* in order to detect GP end. */
309 unsigned long gpnum; /* Highest gp number that this CPU */
310 /* is aware of having started. */
311 unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
312 /* for rcu_all_qs() invocations. */
313 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
314 bool core_needs_qs; /* Core waits for quiesc state. */
315 bool beenonline; /* CPU online at least once. */
316 bool gpwrap; /* Possible gpnum/completed wrap. */
317 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
318 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
319 unsigned long ticks_this_gp; /* The number of scheduling-clock */
320 /* ticks this CPU has handled */
321 /* during and after the last grace */
322 /* period it is aware of. */
323
324 /* 2) batch handling */
325 /*
326 * If nxtlist is not NULL, it is partitioned as follows.
327 * Any of the partitions might be empty, in which case the
328 * pointer to that partition will be equal to the pointer for
329 * the following partition. When the list is empty, all of
330 * the nxttail elements point to the ->nxtlist pointer itself,
331 * which in that case is NULL.
332 *
333 * [nxtlist, *nxttail[RCU_DONE_TAIL]):
334 * Entries that batch # <= ->completed
335 * The grace period for these entries has completed, and
336 * the other grace-period-completed entries may be moved
337 * here temporarily in rcu_process_callbacks().
338 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
339 * Entries that batch # <= ->completed - 1: waiting for current GP
340 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
341 * Entries known to have arrived before current GP ended
342 * [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
343 * Entries that might have arrived after current GP ended
344 * Note that the value of *nxttail[RCU_NEXT_TAIL] will
345 * always be NULL, as this is the end of the list.
346 */
347 struct rcu_head *nxtlist;
348 struct rcu_head **nxttail[RCU_NEXT_SIZE];
349 unsigned long nxtcompleted[RCU_NEXT_SIZE];
350 /* grace periods for sublists. */
351 long qlen_lazy; /* # of lazy queued callbacks */
352 long qlen; /* # of queued callbacks, incl lazy */
353 long qlen_last_fqs_check;
354 /* qlen at last check for QS forcing */
355 unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */
356 unsigned long n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
357 unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
358 unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */
359 unsigned long n_force_qs_snap;
360 /* did other CPU force QS recently? */
361 long blimit; /* Upper limit on a processed batch */
362
363 /* 3) dynticks interface. */
364 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
365 int dynticks_snap; /* Per-GP tracking for dynticks. */
366
367 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
368 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
369 unsigned long offline_fqs; /* Kicked due to being offline. */
370 unsigned long cond_resched_completed;
371 /* Grace period that needs help */
372 /* from cond_resched(). */
373
374 /* 5) __rcu_pending() statistics. */
375 unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */
376 unsigned long n_rp_core_needs_qs;
377 unsigned long n_rp_report_qs;
378 unsigned long n_rp_cb_ready;
379 unsigned long n_rp_cpu_needs_gp;
380 unsigned long n_rp_gp_completed;
381 unsigned long n_rp_gp_started;
382 unsigned long n_rp_nocb_defer_wakeup;
383 unsigned long n_rp_need_nothing;
384
385 /* 6) _rcu_barrier(), OOM callbacks, and expediting. */
386 struct rcu_head barrier_head;
387#ifdef CONFIG_RCU_FAST_NO_HZ
388 struct rcu_head oom_head;
389#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
390 struct mutex exp_funnel_mutex;
391 atomic_long_t expedited_workdone0; /* # done by others #0. */
392 atomic_long_t expedited_workdone1; /* # done by others #1. */
393 atomic_long_t expedited_workdone2; /* # done by others #2. */
394 atomic_long_t expedited_workdone3; /* # done by others #3. */
395
396 /* 7) Callback offloading. */
397#ifdef CONFIG_RCU_NOCB_CPU
398 struct rcu_head *nocb_head; /* CBs waiting for kthread. */
399 struct rcu_head **nocb_tail;
400 atomic_long_t nocb_q_count; /* # CBs waiting for nocb */
401 atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */
402 struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
403 struct rcu_head **nocb_follower_tail;
404 struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
405 struct task_struct *nocb_kthread;
406 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
407
408 /* The following fields are used by the leader, hence own cacheline. */
409 struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
410 /* CBs waiting for GP. */
411 struct rcu_head **nocb_gp_tail;
412 bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */
413 struct rcu_data *nocb_next_follower;
414 /* Next follower in wakeup chain. */
415
416 /* The following fields are used by the follower, hence new cachline. */
417 struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
418 /* Leader CPU takes GP-end wakeups. */
419#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
420
421 /* 8) RCU CPU stall data. */
422 unsigned int softirq_snap; /* Snapshot of softirq activity. */
423
424 int cpu;
425 struct rcu_state *rsp;
426};
427
428/* Values for nocb_defer_wakeup field in struct rcu_data. */
429#define RCU_NOGP_WAKE_NOT 0
430#define RCU_NOGP_WAKE 1
431#define RCU_NOGP_WAKE_FORCE 2
432
433#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
434 /* For jiffies_till_first_fqs and */
435 /* and jiffies_till_next_fqs. */
436
437#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
438 /* delay between bouts of */
439 /* quiescent-state forcing. */
440
441#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
442 /* at least one scheduling clock */
443 /* irq before ratting on them. */
444
445#define rcu_wait(cond) \
446do { \
447 for (;;) { \
448 set_current_state(TASK_INTERRUPTIBLE); \
449 if (cond) \
450 break; \
451 schedule(); \
452 } \
453 __set_current_state(TASK_RUNNING); \
454} while (0)
455
456/*
457 * RCU global state, including node hierarchy. This hierarchy is
458 * represented in "heap" form in a dense array. The root (first level)
459 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
460 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
461 * and the third level in ->node[m+1] and following (->node[m+1] referenced
462 * by ->level[2]). The number of levels is determined by the number of
463 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
464 * consisting of a single rcu_node.
465 */
466struct rcu_state {
467 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
468 struct rcu_node *level[RCU_NUM_LVLS + 1];
469 /* Hierarchy levels (+1 to */
470 /* shut bogus gcc warning) */
471 u8 flavor_mask; /* bit in flavor mask. */
472 struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
473 call_rcu_func_t call; /* call_rcu() flavor. */
474 int ncpus; /* # CPUs seen so far. */
475
476 /* The following fields are guarded by the root rcu_node's lock. */
477
478 u8 boost ____cacheline_internodealigned_in_smp;
479 /* Subject to priority boost. */
480 unsigned long gpnum; /* Current gp number. */
481 unsigned long completed; /* # of last completed gp. */
482 struct task_struct *gp_kthread; /* Task for grace periods. */
483 struct swait_queue_head gp_wq; /* Where GP task waits. */
484 short gp_flags; /* Commands for GP task. */
485 short gp_state; /* GP kthread sleep state. */
486
487 /* End of fields guarded by root rcu_node's lock. */
488
489 raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;
490 /* Protect following fields. */
491 struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */
492 /* need a grace period. */
493 struct rcu_head **orphan_nxttail; /* Tail of above. */
494 struct rcu_head *orphan_donelist; /* Orphaned callbacks that */
495 /* are ready to invoke. */
496 struct rcu_head **orphan_donetail; /* Tail of above. */
497 long qlen_lazy; /* Number of lazy callbacks. */
498 long qlen; /* Total number of callbacks. */
499 /* End of fields guarded by orphan_lock. */
500
501 struct mutex barrier_mutex; /* Guards barrier fields. */
502 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
503 struct completion barrier_completion; /* Wake at barrier end. */
504 unsigned long barrier_sequence; /* ++ at start and end of */
505 /* _rcu_barrier(). */
506 /* End of fields guarded by barrier_mutex. */
507
508 unsigned long expedited_sequence; /* Take a ticket. */
509 atomic_long_t expedited_normal; /* # fallbacks to normal. */
510 atomic_t expedited_need_qs; /* # CPUs left to check in. */
511 struct swait_queue_head expedited_wq; /* Wait for check-ins. */
512 int ncpus_snap; /* # CPUs seen last time. */
513
514 unsigned long jiffies_force_qs; /* Time at which to invoke */
515 /* force_quiescent_state(). */
516 unsigned long n_force_qs; /* Number of calls to */
517 /* force_quiescent_state(). */
518 unsigned long n_force_qs_lh; /* ~Number of calls leaving */
519 /* due to lock unavailable. */
520 unsigned long n_force_qs_ngp; /* Number of calls leaving */
521 /* due to no GP active. */
522 unsigned long gp_start; /* Time at which GP started, */
523 /* but in jiffies. */
524 unsigned long gp_activity; /* Time of last GP kthread */
525 /* activity in jiffies. */
526 unsigned long jiffies_stall; /* Time at which to check */
527 /* for CPU stalls. */
528 unsigned long jiffies_resched; /* Time at which to resched */
529 /* a reluctant CPU. */
530 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
531 /* GP start. */
532 unsigned long gp_max; /* Maximum GP duration in */
533 /* jiffies. */
534 const char *name; /* Name of structure. */
535 char abbr; /* Abbreviated name. */
536 struct list_head flavors; /* List of RCU flavors. */
537};
538
539/* Values for rcu_state structure's gp_flags field. */
540#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
541#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
542
543/* Values for rcu_state structure's gp_state field. */
544#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
545#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
546#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
547#define RCU_GP_WAIT_FQS 3 /* Wait for force-quiescent-state time. */
548#define RCU_GP_DOING_FQS 4 /* Wait done for force-quiescent-state time. */
549#define RCU_GP_CLEANUP 5 /* Grace-period cleanup started. */
550#define RCU_GP_CLEANED 6 /* Grace-period cleanup complete. */
551
552#ifndef RCU_TREE_NONCORE
553static const char * const gp_state_names[] = {
554 "RCU_GP_IDLE",
555 "RCU_GP_WAIT_GPS",
556 "RCU_GP_DONE_GPS",
557 "RCU_GP_WAIT_FQS",
558 "RCU_GP_DOING_FQS",
559 "RCU_GP_CLEANUP",
560 "RCU_GP_CLEANED",
561};
562#endif /* #ifndef RCU_TREE_NONCORE */
563
564extern struct list_head rcu_struct_flavors;
565
566/* Sequence through rcu_state structures for each RCU flavor. */
567#define for_each_rcu_flavor(rsp) \
568 list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
569
570/*
571 * RCU implementation internal declarations:
572 */
573extern struct rcu_state rcu_sched_state;
574
575extern struct rcu_state rcu_bh_state;
576
577#ifdef CONFIG_PREEMPT_RCU
578extern struct rcu_state rcu_preempt_state;
579#endif /* #ifdef CONFIG_PREEMPT_RCU */
580
581#ifdef CONFIG_RCU_BOOST
582DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
583DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
584DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
585DECLARE_PER_CPU(char, rcu_cpu_has_work);
586#endif /* #ifdef CONFIG_RCU_BOOST */
587
588#ifndef RCU_TREE_NONCORE
589
590/* Forward declarations for rcutree_plugin.h */
591static void rcu_bootup_announce(void);
592static void rcu_preempt_note_context_switch(void);
593static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
594#ifdef CONFIG_HOTPLUG_CPU
595static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
596#endif /* #ifdef CONFIG_HOTPLUG_CPU */
597static void rcu_print_detail_task_stall(struct rcu_state *rsp);
598static int rcu_print_task_stall(struct rcu_node *rnp);
599static int rcu_print_task_exp_stall(struct rcu_node *rnp);
600static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
601static void rcu_preempt_check_callbacks(void);
602void call_rcu(struct rcu_head *head, rcu_callback_t func);
603static void __init __rcu_init_preempt(void);
604static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
605static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
606static void invoke_rcu_callbacks_kthread(void);
607static bool rcu_is_callbacks_kthread(void);
608#ifdef CONFIG_RCU_BOOST
609static void rcu_preempt_do_callbacks(void);
610static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
611 struct rcu_node *rnp);
612#endif /* #ifdef CONFIG_RCU_BOOST */
613static void __init rcu_spawn_boost_kthreads(void);
614static void rcu_prepare_kthreads(int cpu);
615static void rcu_cleanup_after_idle(void);
616static void rcu_prepare_for_idle(void);
617static void rcu_idle_count_callbacks_posted(void);
618static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
619static void print_cpu_stall_info_begin(void);
620static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
621static void print_cpu_stall_info_end(void);
622static void zero_cpu_stall_ticks(struct rcu_data *rdp);
623static void increment_cpu_stall_ticks(void);
624static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
625static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
626static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
627static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
628static void rcu_init_one_nocb(struct rcu_node *rnp);
629static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
630 bool lazy, unsigned long flags);
631static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
632 struct rcu_data *rdp,
633 unsigned long flags);
634static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
635static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
636static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
637static void rcu_spawn_all_nocb_kthreads(int cpu);
638static void __init rcu_spawn_nocb_kthreads(void);
639#ifdef CONFIG_RCU_NOCB_CPU
640static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
641#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
642static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
643static bool init_nocb_callback_list(struct rcu_data *rdp);
644static void rcu_sysidle_enter(int irq);
645static void rcu_sysidle_exit(int irq);
646static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
647 unsigned long *maxj);
648static bool is_sysidle_rcu_state(struct rcu_state *rsp);
649static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
650 unsigned long maxj);
651static void rcu_bind_gp_kthread(void);
652static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp);
653static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
654static void rcu_dynticks_task_enter(void);
655static void rcu_dynticks_task_exit(void);
656
657#endif /* #ifndef RCU_TREE_NONCORE */
658
659#ifdef CONFIG_RCU_TRACE
660/* Read out queue lengths for tracing. */
661static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
662{
663#ifdef CONFIG_RCU_NOCB_CPU
664 *ql = atomic_long_read(&rdp->nocb_q_count);
665 *qll = atomic_long_read(&rdp->nocb_q_count_lazy);
666#else /* #ifdef CONFIG_RCU_NOCB_CPU */
667 *ql = 0;
668 *qll = 0;
669#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
670}
671#endif /* #ifdef CONFIG_RCU_TRACE */
672
673/*
674 * Place this after a lock-acquisition primitive to guarantee that
675 * an UNLOCK+LOCK pair act as a full barrier. This guarantee applies
676 * if the UNLOCK and LOCK are executed by the same CPU or if the
677 * UNLOCK and LOCK operate on the same lock variable.
678 */
679#ifdef CONFIG_PPC
680#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */
681#else /* #ifdef CONFIG_PPC */
682#define smp_mb__after_unlock_lock() do { } while (0)
683#endif /* #else #ifdef CONFIG_PPC */
684
685/*
686 * Wrappers for the rcu_node::lock acquire and release.
687 *
688 * Because the rcu_nodes form a tree, the tree traversal locking will observe
689 * different lock values, this in turn means that an UNLOCK of one level
690 * followed by a LOCK of another level does not imply a full memory barrier;
691 * and most importantly transitivity is lost.
692 *
693 * In order to restore full ordering between tree levels, augment the regular
694 * lock acquire functions with smp_mb__after_unlock_lock().
695 *
696 * As ->lock of struct rcu_node is a __private field, therefore one should use
697 * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
698 */
699static inline void raw_spin_lock_rcu_node(struct rcu_node *rnp)
700{
701 raw_spin_lock(&ACCESS_PRIVATE(rnp, lock));
702 smp_mb__after_unlock_lock();
703}
704
705static inline void raw_spin_unlock_rcu_node(struct rcu_node *rnp)
706{
707 raw_spin_unlock(&ACCESS_PRIVATE(rnp, lock));
708}
709
710static inline void raw_spin_lock_irq_rcu_node(struct rcu_node *rnp)
711{
712 raw_spin_lock_irq(&ACCESS_PRIVATE(rnp, lock));
713 smp_mb__after_unlock_lock();
714}
715
716static inline void raw_spin_unlock_irq_rcu_node(struct rcu_node *rnp)
717{
718 raw_spin_unlock_irq(&ACCESS_PRIVATE(rnp, lock));
719}
720
721#define raw_spin_lock_irqsave_rcu_node(rnp, flags) \
722do { \
723 typecheck(unsigned long, flags); \
724 raw_spin_lock_irqsave(&ACCESS_PRIVATE(rnp, lock), flags); \
725 smp_mb__after_unlock_lock(); \
726} while (0)
727
728#define raw_spin_unlock_irqrestore_rcu_node(rnp, flags) \
729do { \
730 typecheck(unsigned long, flags); \
731 raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(rnp, lock), flags); \
732} while (0)
733
734static inline bool raw_spin_trylock_rcu_node(struct rcu_node *rnp)
735{
736 bool locked = raw_spin_trylock(&ACCESS_PRIVATE(rnp, lock));
737
738 if (locked)
739 smp_mb__after_unlock_lock();
740 return locked;
741}
1/* SPDX-License-Identifier: GPL-2.0+ */
2/*
3 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
4 * Internal non-public definitions.
5 *
6 * Copyright IBM Corporation, 2008
7 *
8 * Author: Ingo Molnar <mingo@elte.hu>
9 * Paul E. McKenney <paulmck@linux.ibm.com>
10 */
11
12#include <linux/cache.h>
13#include <linux/spinlock.h>
14#include <linux/rtmutex.h>
15#include <linux/threads.h>
16#include <linux/cpumask.h>
17#include <linux/seqlock.h>
18#include <linux/swait.h>
19#include <linux/rcu_node_tree.h>
20
21#include "rcu_segcblist.h"
22
23/* Communicate arguments to a workqueue handler. */
24struct rcu_exp_work {
25 unsigned long rew_s;
26 struct work_struct rew_work;
27};
28
29/* RCU's kthread states for tracing. */
30#define RCU_KTHREAD_STOPPED 0
31#define RCU_KTHREAD_RUNNING 1
32#define RCU_KTHREAD_WAITING 2
33#define RCU_KTHREAD_OFFCPU 3
34#define RCU_KTHREAD_YIELDING 4
35#define RCU_KTHREAD_MAX 4
36
37/*
38 * Definition for node within the RCU grace-period-detection hierarchy.
39 */
40struct rcu_node {
41 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
42 /* some rcu_state fields as well as */
43 /* following. */
44 unsigned long gp_seq; /* Track rsp->gp_seq. */
45 unsigned long gp_seq_needed; /* Track furthest future GP request. */
46 unsigned long completedqs; /* All QSes done for this node. */
47 unsigned long qsmask; /* CPUs or groups that need to switch in */
48 /* order for current grace period to proceed.*/
49 /* In leaf rcu_node, each bit corresponds to */
50 /* an rcu_data structure, otherwise, each */
51 /* bit corresponds to a child rcu_node */
52 /* structure. */
53 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
54 unsigned long qsmaskinit;
55 /* Per-GP initial value for qsmask. */
56 /* Initialized from ->qsmaskinitnext at the */
57 /* beginning of each grace period. */
58 unsigned long qsmaskinitnext;
59 /* Online CPUs for next grace period. */
60 unsigned long expmask; /* CPUs or groups that need to check in */
61 /* to allow the current expedited GP */
62 /* to complete. */
63 unsigned long expmaskinit;
64 /* Per-GP initial values for expmask. */
65 /* Initialized from ->expmaskinitnext at the */
66 /* beginning of each expedited GP. */
67 unsigned long expmaskinitnext;
68 /* Online CPUs for next expedited GP. */
69 /* Any CPU that has ever been online will */
70 /* have its bit set. */
71 unsigned long cbovldmask;
72 /* CPUs experiencing callback overload. */
73 unsigned long ffmask; /* Fully functional CPUs. */
74 unsigned long grpmask; /* Mask to apply to parent qsmask. */
75 /* Only one bit will be set in this mask. */
76 int grplo; /* lowest-numbered CPU here. */
77 int grphi; /* highest-numbered CPU here. */
78 u8 grpnum; /* group number for next level up. */
79 u8 level; /* root is at level 0. */
80 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
81 /* exit RCU read-side critical sections */
82 /* before propagating offline up the */
83 /* rcu_node tree? */
84 struct rcu_node *parent;
85 struct list_head blkd_tasks;
86 /* Tasks blocked in RCU read-side critical */
87 /* section. Tasks are placed at the head */
88 /* of this list and age towards the tail. */
89 struct list_head *gp_tasks;
90 /* Pointer to the first task blocking the */
91 /* current grace period, or NULL if there */
92 /* is no such task. */
93 struct list_head *exp_tasks;
94 /* Pointer to the first task blocking the */
95 /* current expedited grace period, or NULL */
96 /* if there is no such task. If there */
97 /* is no current expedited grace period, */
98 /* then there can cannot be any such task. */
99 struct list_head *boost_tasks;
100 /* Pointer to first task that needs to be */
101 /* priority boosted, or NULL if no priority */
102 /* boosting is needed for this rcu_node */
103 /* structure. If there are no tasks */
104 /* queued on this rcu_node structure that */
105 /* are blocking the current grace period, */
106 /* there can be no such task. */
107 struct rt_mutex boost_mtx;
108 /* Used only for the priority-boosting */
109 /* side effect, not as a lock. */
110 unsigned long boost_time;
111 /* When to start boosting (jiffies). */
112 struct task_struct *boost_kthread_task;
113 /* kthread that takes care of priority */
114 /* boosting for this rcu_node structure. */
115 unsigned int boost_kthread_status;
116 /* State of boost_kthread_task for tracing. */
117#ifdef CONFIG_RCU_NOCB_CPU
118 struct swait_queue_head nocb_gp_wq[2];
119 /* Place for rcu_nocb_kthread() to wait GP. */
120#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
121 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
122
123 spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
124 unsigned long exp_seq_rq;
125 wait_queue_head_t exp_wq[4];
126 struct rcu_exp_work rew;
127 bool exp_need_flush; /* Need to flush workitem? */
128} ____cacheline_internodealigned_in_smp;
129
130/*
131 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
132 * are indexed relative to this interval rather than the global CPU ID space.
133 * This generates the bit for a CPU in node-local masks.
134 */
135#define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
136
137/*
138 * Union to allow "aggregate OR" operation on the need for a quiescent
139 * state by the normal and expedited grace periods.
140 */
141union rcu_noqs {
142 struct {
143 u8 norm;
144 u8 exp;
145 } b; /* Bits. */
146 u16 s; /* Set of bits, aggregate OR here. */
147};
148
149/* Per-CPU data for read-copy update. */
150struct rcu_data {
151 /* 1) quiescent-state and grace-period handling : */
152 unsigned long gp_seq; /* Track rsp->gp_seq counter. */
153 unsigned long gp_seq_needed; /* Track furthest future GP request. */
154 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
155 bool core_needs_qs; /* Core waits for quiesc state. */
156 bool beenonline; /* CPU online at least once. */
157 bool gpwrap; /* Possible ->gp_seq wrap. */
158 bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */
159 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
160 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
161 unsigned long ticks_this_gp; /* The number of scheduling-clock */
162 /* ticks this CPU has handled */
163 /* during and after the last grace */
164 /* period it is aware of. */
165 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
166 bool defer_qs_iw_pending; /* Scheduler attention pending? */
167
168 /* 2) batch handling */
169 struct rcu_segcblist cblist; /* Segmented callback list, with */
170 /* different callbacks waiting for */
171 /* different grace periods. */
172 long qlen_last_fqs_check;
173 /* qlen at last check for QS forcing */
174 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
175 unsigned long n_force_qs_snap;
176 /* did other CPU force QS recently? */
177 long blimit; /* Upper limit on a processed batch */
178
179 /* 3) dynticks interface. */
180 int dynticks_snap; /* Per-GP tracking for dynticks. */
181 long dynticks_nesting; /* Track process nesting level. */
182 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
183 atomic_t dynticks; /* Even value for idle, else odd. */
184 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
185 bool rcu_urgent_qs; /* GP old need light quiescent state. */
186 bool rcu_forced_tick; /* Forced tick to provide QS. */
187 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
188#ifdef CONFIG_RCU_FAST_NO_HZ
189 unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */
190 unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */
191 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
192#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
193
194 /* 4) rcu_barrier(), OOM callbacks, and expediting. */
195 struct rcu_head barrier_head;
196 int exp_dynticks_snap; /* Double-check need for IPI. */
197
198 /* 5) Callback offloading. */
199#ifdef CONFIG_RCU_NOCB_CPU
200 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
201 struct task_struct *nocb_gp_kthread;
202 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
203 atomic_t nocb_lock_contended; /* Contention experienced. */
204 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
205 struct timer_list nocb_timer; /* Enforce finite deferral. */
206 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
207
208 /* The following fields are used by call_rcu, hence own cacheline. */
209 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
210 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
211 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
212 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
213 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
214
215 /* The following fields are used by GP kthread, hence own cacheline. */
216 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
217 struct timer_list nocb_bypass_timer; /* Force nocb_bypass flush. */
218 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
219 u8 nocb_gp_bypass; /* Found a bypass on last scan? */
220 u8 nocb_gp_gp; /* GP to wait for on last scan? */
221 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */
222 unsigned long nocb_gp_loops; /* # passes through wait code. */
223 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
224 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
225 struct task_struct *nocb_cb_kthread;
226 struct rcu_data *nocb_next_cb_rdp;
227 /* Next rcu_data in wakeup chain. */
228
229 /* The following fields are used by CB kthread, hence new cacheline. */
230 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
231 /* GP rdp takes GP-end wakeups. */
232#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
233
234 /* 6) RCU priority boosting. */
235 struct task_struct *rcu_cpu_kthread_task;
236 /* rcuc per-CPU kthread or NULL. */
237 unsigned int rcu_cpu_kthread_status;
238 char rcu_cpu_has_work;
239
240 /* 7) Diagnostic data, including RCU CPU stall warnings. */
241 unsigned int softirq_snap; /* Snapshot of softirq activity. */
242 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
243 struct irq_work rcu_iw; /* Check for non-irq activity. */
244 bool rcu_iw_pending; /* Is ->rcu_iw pending? */
245 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
246 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
247 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */
248 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
249 short rcu_onl_gp_flags; /* ->gp_flags at last online. */
250 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
251
252 int cpu;
253};
254
255/* Values for nocb_defer_wakeup field in struct rcu_data. */
256#define RCU_NOCB_WAKE_NOT 0
257#define RCU_NOCB_WAKE 1
258#define RCU_NOCB_WAKE_FORCE 2
259
260#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
261 /* For jiffies_till_first_fqs and */
262 /* and jiffies_till_next_fqs. */
263
264#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
265 /* delay between bouts of */
266 /* quiescent-state forcing. */
267
268#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
269 /* at least one scheduling clock */
270 /* irq before ratting on them. */
271
272#define rcu_wait(cond) \
273do { \
274 for (;;) { \
275 set_current_state(TASK_INTERRUPTIBLE); \
276 if (cond) \
277 break; \
278 schedule(); \
279 } \
280 __set_current_state(TASK_RUNNING); \
281} while (0)
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 */
293struct rcu_state {
294 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
295 struct rcu_node *level[RCU_NUM_LVLS + 1];
296 /* Hierarchy levels (+1 to */
297 /* shut bogus gcc warning) */
298 int ncpus; /* # CPUs seen so far. */
299
300 /* The following fields are guarded by the root rcu_node's lock. */
301
302 u8 boost ____cacheline_internodealigned_in_smp;
303 /* Subject to priority boost. */
304 unsigned long gp_seq; /* Grace-period sequence #. */
305 unsigned long gp_max; /* Maximum GP duration in */
306 /* jiffies. */
307 struct task_struct *gp_kthread; /* Task for grace periods. */
308 struct swait_queue_head gp_wq; /* Where GP task waits. */
309 short gp_flags; /* Commands for GP task. */
310 short gp_state; /* GP kthread sleep state. */
311 unsigned long gp_wake_time; /* Last GP kthread wake. */
312 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
313
314 /* End of fields guarded by root rcu_node's lock. */
315
316 struct mutex barrier_mutex; /* Guards barrier fields. */
317 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
318 struct completion barrier_completion; /* Wake at barrier end. */
319 unsigned long barrier_sequence; /* ++ at start and end of */
320 /* rcu_barrier(). */
321 /* End of fields guarded by barrier_mutex. */
322
323 struct mutex exp_mutex; /* Serialize expedited GP. */
324 struct mutex exp_wake_mutex; /* Serialize wakeup. */
325 unsigned long expedited_sequence; /* Take a ticket. */
326 atomic_t expedited_need_qs; /* # CPUs left to check in. */
327 struct swait_queue_head expedited_wq; /* Wait for check-ins. */
328 int ncpus_snap; /* # CPUs seen last time. */
329 u8 cbovld; /* Callback overload now? */
330 u8 cbovldnext; /* ^ ^ next time? */
331
332 unsigned long jiffies_force_qs; /* Time at which to invoke */
333 /* force_quiescent_state(). */
334 unsigned long jiffies_kick_kthreads; /* Time at which to kick */
335 /* kthreads, if configured. */
336 unsigned long n_force_qs; /* Number of calls to */
337 /* force_quiescent_state(). */
338 unsigned long gp_start; /* Time at which GP started, */
339 /* but in jiffies. */
340 unsigned long gp_end; /* Time last GP ended, again */
341 /* in jiffies. */
342 unsigned long gp_activity; /* Time of last GP kthread */
343 /* activity in jiffies. */
344 unsigned long gp_req_activity; /* Time of last GP request */
345 /* in jiffies. */
346 unsigned long jiffies_stall; /* Time at which to check */
347 /* for CPU stalls. */
348 unsigned long jiffies_resched; /* Time at which to resched */
349 /* a reluctant CPU. */
350 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
351 /* GP start. */
352 const char *name; /* Name of structure. */
353 char abbr; /* Abbreviated name. */
354
355 raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
356 /* Synchronize offline with */
357 /* GP pre-initialization. */
358};
359
360/* Values for rcu_state structure's gp_flags field. */
361#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
362#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
363#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
364
365/* Values for rcu_state structure's gp_state field. */
366#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
367#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
368#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
369#define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
370#define RCU_GP_INIT 4 /* Grace-period initialization. */
371#define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
372#define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
373#define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
374#define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
375
376/*
377 * In order to export the rcu_state name to the tracing tools, it
378 * needs to be added in the __tracepoint_string section.
379 * This requires defining a separate variable tp_<sname>_varname
380 * that points to the string being used, and this will allow
381 * the tracing userspace tools to be able to decipher the string
382 * address to the matching string.
383 */
384#ifdef CONFIG_PREEMPT_RCU
385#define RCU_ABBR 'p'
386#define RCU_NAME_RAW "rcu_preempt"
387#else /* #ifdef CONFIG_PREEMPT_RCU */
388#define RCU_ABBR 's'
389#define RCU_NAME_RAW "rcu_sched"
390#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
391#ifndef CONFIG_TRACING
392#define RCU_NAME RCU_NAME_RAW
393#else /* #ifdef CONFIG_TRACING */
394static char rcu_name[] = RCU_NAME_RAW;
395static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
396#define RCU_NAME rcu_name
397#endif /* #else #ifdef CONFIG_TRACING */
398
399/* Forward declarations for tree_plugin.h */
400static void rcu_bootup_announce(void);
401static void rcu_qs(void);
402static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
403#ifdef CONFIG_HOTPLUG_CPU
404static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
405#endif /* #ifdef CONFIG_HOTPLUG_CPU */
406static int rcu_print_task_exp_stall(struct rcu_node *rnp);
407static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
408static void rcu_flavor_sched_clock_irq(int user);
409static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
410static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
411static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
412static bool rcu_is_callbacks_kthread(void);
413static void rcu_cpu_kthread_setup(unsigned int cpu);
414static void __init rcu_spawn_boost_kthreads(void);
415static void rcu_prepare_kthreads(int cpu);
416static void rcu_cleanup_after_idle(void);
417static void rcu_prepare_for_idle(void);
418static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
419static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
420static void rcu_preempt_deferred_qs(struct task_struct *t);
421static void zero_cpu_stall_ticks(struct rcu_data *rdp);
422static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
423static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
424static void rcu_init_one_nocb(struct rcu_node *rnp);
425static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
426 unsigned long j);
427static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
428 bool *was_alldone, unsigned long flags);
429static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
430 unsigned long flags);
431static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
432static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
433static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
434static void rcu_spawn_cpu_nocb_kthread(int cpu);
435static void __init rcu_spawn_nocb_kthreads(void);
436static void show_rcu_nocb_state(struct rcu_data *rdp);
437static void rcu_nocb_lock(struct rcu_data *rdp);
438static void rcu_nocb_unlock(struct rcu_data *rdp);
439static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
440 unsigned long flags);
441static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
442#ifdef CONFIG_RCU_NOCB_CPU
443static void __init rcu_organize_nocb_kthreads(void);
444#define rcu_nocb_lock_irqsave(rdp, flags) \
445do { \
446 if (!rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
447 local_irq_save(flags); \
448 else \
449 raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags)); \
450} while (0)
451#else /* #ifdef CONFIG_RCU_NOCB_CPU */
452#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
453#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
454
455static void rcu_bind_gp_kthread(void);
456static bool rcu_nohz_full_cpu(void);
457static void rcu_dynticks_task_enter(void);
458static void rcu_dynticks_task_exit(void);
459static void rcu_dynticks_task_trace_enter(void);
460static void rcu_dynticks_task_trace_exit(void);
461
462/* Forward declarations for tree_stall.h */
463static void record_gp_stall_check_time(void);
464static void rcu_iw_handler(struct irq_work *iwp);
465static void check_cpu_stall(struct rcu_data *rdp);
466static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
467 const unsigned long gpssdelay);