1 /* SPDX-License-Identifier: GPL-2.0+ */ 1 /* SPDX-License-Identifier: GPL-2.0+ */
2 /* 2 /*
3 * Read-Copy Update mechanism for mutual exclu 3 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
4 * Internal non-public definitions. 4 * Internal non-public definitions.
5 * 5 *
6 * Copyright IBM Corporation, 2008 6 * Copyright IBM Corporation, 2008
7 * 7 *
8 * Author: Ingo Molnar <mingo@elte.hu> 8 * Author: Ingo Molnar <mingo@elte.hu>
9 * Paul E. McKenney <paulmck@linux.ibm 9 * Paul E. McKenney <paulmck@linux.ibm.com>
10 */ 10 */
11 11
12 #include <linux/cache.h> 12 #include <linux/cache.h>
13 #include <linux/kthread.h> <<
14 #include <linux/spinlock.h> 13 #include <linux/spinlock.h>
15 #include <linux/rtmutex.h> 14 #include <linux/rtmutex.h>
16 #include <linux/threads.h> 15 #include <linux/threads.h>
17 #include <linux/cpumask.h> 16 #include <linux/cpumask.h>
18 #include <linux/seqlock.h> 17 #include <linux/seqlock.h>
19 #include <linux/swait.h> 18 #include <linux/swait.h>
20 #include <linux/rcu_node_tree.h> 19 #include <linux/rcu_node_tree.h>
21 20
22 #include "rcu_segcblist.h" 21 #include "rcu_segcblist.h"
23 22
24 /* Communicate arguments to a kthread worker h !! 23 /* Communicate arguments to a workqueue handler. */
25 struct rcu_exp_work { 24 struct rcu_exp_work {
26 unsigned long rew_s; 25 unsigned long rew_s;
27 struct kthread_work rew_work; !! 26 struct work_struct rew_work;
28 }; 27 };
29 28
30 /* RCU's kthread states for tracing. */ 29 /* RCU's kthread states for tracing. */
31 #define RCU_KTHREAD_STOPPED 0 30 #define RCU_KTHREAD_STOPPED 0
32 #define RCU_KTHREAD_RUNNING 1 31 #define RCU_KTHREAD_RUNNING 1
33 #define RCU_KTHREAD_WAITING 2 32 #define RCU_KTHREAD_WAITING 2
34 #define RCU_KTHREAD_OFFCPU 3 33 #define RCU_KTHREAD_OFFCPU 3
35 #define RCU_KTHREAD_YIELDING 4 34 #define RCU_KTHREAD_YIELDING 4
36 #define RCU_KTHREAD_MAX 4 35 #define RCU_KTHREAD_MAX 4
37 36
38 /* 37 /*
39 * Definition for node within the RCU grace-pe 38 * Definition for node within the RCU grace-period-detection hierarchy.
40 */ 39 */
41 struct rcu_node { 40 struct rcu_node {
42 raw_spinlock_t __private lock; /* Roo 41 raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
43 /* so 42 /* some rcu_state fields as well as */
44 /* fo 43 /* following. */
45 unsigned long gp_seq; /* Track rsp-> 44 unsigned long gp_seq; /* Track rsp->gp_seq. */
46 unsigned long gp_seq_needed; /* Track 45 unsigned long gp_seq_needed; /* Track furthest future GP request. */
47 unsigned long completedqs; /* All QSes 46 unsigned long completedqs; /* All QSes done for this node. */
48 unsigned long qsmask; /* CPUs or gro 47 unsigned long qsmask; /* CPUs or groups that need to switch in */
49 /* order for 48 /* order for current grace period to proceed.*/
50 /* In leaf rc 49 /* In leaf rcu_node, each bit corresponds to */
51 /* an rcu_dat 50 /* an rcu_data structure, otherwise, each */
52 /* bit corres 51 /* bit corresponds to a child rcu_node */
53 /* structure. 52 /* structure. */
54 unsigned long rcu_gp_init_mask; /* Mas 53 unsigned long rcu_gp_init_mask; /* Mask of offline CPUs at GP init. */
55 unsigned long qsmaskinit; 54 unsigned long qsmaskinit;
56 /* Per-GP init 55 /* Per-GP initial value for qsmask. */
57 /* Initialize 56 /* Initialized from ->qsmaskinitnext at the */
58 /* beginning 57 /* beginning of each grace period. */
59 unsigned long qsmaskinitnext; 58 unsigned long qsmaskinitnext;
>> 59 unsigned long ofl_seq; /* CPU-hotplug operation sequence count. */
>> 60 /* Online CPUs for next grace period. */
60 unsigned long expmask; /* CPUs or gro 61 unsigned long expmask; /* CPUs or groups that need to check in */
61 /* to allow t 62 /* to allow the current expedited GP */
62 /* to complet 63 /* to complete. */
63 unsigned long expmaskinit; 64 unsigned long expmaskinit;
64 /* Per-GP init 65 /* Per-GP initial values for expmask. */
65 /* Initialize 66 /* Initialized from ->expmaskinitnext at the */
66 /* beginning 67 /* beginning of each expedited GP. */
67 unsigned long expmaskinitnext; 68 unsigned long expmaskinitnext;
68 /* Online CPUs 69 /* Online CPUs for next expedited GP. */
69 /* Any CPU th 70 /* Any CPU that has ever been online will */
70 /* have its b 71 /* have its bit set. */
71 struct kthread_worker *exp_kworker; <<
72 /* Workers per <<
73 /* initializat <<
74 unsigned long cbovldmask; 72 unsigned long cbovldmask;
75 /* CPUs experi 73 /* CPUs experiencing callback overload. */
76 unsigned long ffmask; /* Fully funct 74 unsigned long ffmask; /* Fully functional CPUs. */
77 unsigned long grpmask; /* Mask to app 75 unsigned long grpmask; /* Mask to apply to parent qsmask. */
78 /* Only one b 76 /* Only one bit will be set in this mask. */
79 int grplo; /* lowest-numb 77 int grplo; /* lowest-numbered CPU here. */
80 int grphi; /* highest-num 78 int grphi; /* highest-numbered CPU here. */
81 u8 grpnum; /* group numbe 79 u8 grpnum; /* group number for next level up. */
82 u8 level; /* root is at 80 u8 level; /* root is at level 0. */
83 bool wait_blkd_tasks;/* Necessary t 81 bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
84 /* exit RCU r 82 /* exit RCU read-side critical sections */
85 /* before pro 83 /* before propagating offline up the */
86 /* rcu_node t 84 /* rcu_node tree? */
87 struct rcu_node *parent; 85 struct rcu_node *parent;
88 struct list_head blkd_tasks; 86 struct list_head blkd_tasks;
89 /* Tasks block 87 /* Tasks blocked in RCU read-side critical */
90 /* section. 88 /* section. Tasks are placed at the head */
91 /* of this li 89 /* of this list and age towards the tail. */
92 struct list_head *gp_tasks; 90 struct list_head *gp_tasks;
93 /* Pointer to 91 /* Pointer to the first task blocking the */
94 /* current gr 92 /* current grace period, or NULL if there */
95 /* is no such 93 /* is no such task. */
96 struct list_head *exp_tasks; 94 struct list_head *exp_tasks;
97 /* Pointer to 95 /* Pointer to the first task blocking the */
98 /* current ex 96 /* current expedited grace period, or NULL */
99 /* if there i 97 /* if there is no such task. If there */
100 /* is no curr 98 /* is no current expedited grace period, */
101 /* then there 99 /* then there can cannot be any such task. */
102 struct list_head *boost_tasks; 100 struct list_head *boost_tasks;
103 /* Pointer to 101 /* Pointer to first task that needs to be */
104 /* priority b 102 /* priority boosted, or NULL if no priority */
105 /* boosting i 103 /* boosting is needed for this rcu_node */
106 /* structure. 104 /* structure. If there are no tasks */
107 /* queued on 105 /* queued on this rcu_node structure that */
108 /* are blocki 106 /* are blocking the current grace period, */
109 /* there can 107 /* there can be no such task. */
110 struct rt_mutex boost_mtx; 108 struct rt_mutex boost_mtx;
111 /* Used only f 109 /* Used only for the priority-boosting */
112 /* side effec 110 /* side effect, not as a lock. */
113 unsigned long boost_time; 111 unsigned long boost_time;
114 /* When to sta 112 /* When to start boosting (jiffies). */
115 struct mutex kthread_mutex; <<
116 /* Exclusion f <<
117 /* manipulati <<
118 struct task_struct *boost_kthread_task 113 struct task_struct *boost_kthread_task;
119 /* kthread tha 114 /* kthread that takes care of priority */
120 /* boosting f 115 /* boosting for this rcu_node structure. */
121 unsigned int boost_kthread_status; 116 unsigned int boost_kthread_status;
122 /* State of bo 117 /* State of boost_kthread_task for tracing. */
123 unsigned long n_boosts; /* Number of b <<
124 #ifdef CONFIG_RCU_NOCB_CPU 118 #ifdef CONFIG_RCU_NOCB_CPU
125 struct swait_queue_head nocb_gp_wq[2]; 119 struct swait_queue_head nocb_gp_wq[2];
126 /* Place for r 120 /* Place for rcu_nocb_kthread() to wait GP. */
127 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 121 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
128 raw_spinlock_t fqslock ____cacheline_i 122 raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
129 123
130 spinlock_t exp_lock ____cacheline_inte 124 spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
131 unsigned long exp_seq_rq; 125 unsigned long exp_seq_rq;
132 wait_queue_head_t exp_wq[4]; 126 wait_queue_head_t exp_wq[4];
133 struct rcu_exp_work rew; 127 struct rcu_exp_work rew;
134 bool exp_need_flush; /* Need to flu 128 bool exp_need_flush; /* Need to flush workitem? */
135 raw_spinlock_t exp_poll_lock; <<
136 /* Lock and da <<
137 unsigned long exp_seq_poll_rq; <<
138 struct work_struct exp_poll_wq; <<
139 } ____cacheline_internodealigned_in_smp; 129 } ____cacheline_internodealigned_in_smp;
140 130
141 /* 131 /*
142 * Bitmasks in an rcu_node cover the interval 132 * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
143 * are indexed relative to this interval rathe 133 * are indexed relative to this interval rather than the global CPU ID space.
144 * This generates the bit for a CPU in node-lo 134 * This generates the bit for a CPU in node-local masks.
145 */ 135 */
146 #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) 136 #define leaf_node_cpu_bit(rnp, cpu) (BIT((cpu) - (rnp)->grplo))
147 137
148 /* 138 /*
149 * Union to allow "aggregate OR" operation on 139 * Union to allow "aggregate OR" operation on the need for a quiescent
150 * state by the normal and expedited grace per 140 * state by the normal and expedited grace periods.
151 */ 141 */
152 union rcu_noqs { 142 union rcu_noqs {
153 struct { 143 struct {
154 u8 norm; 144 u8 norm;
155 u8 exp; 145 u8 exp;
156 } b; /* Bits. */ 146 } b; /* Bits. */
157 u16 s; /* Set of bits, aggregate OR he 147 u16 s; /* Set of bits, aggregate OR here. */
158 }; 148 };
159 149
160 /* <<
161 * Record the snapshot of the core stats at ha <<
162 * The member gp_seq is used to ensure that al <<
163 * during the sampling period. The snapshot is <<
164 * equal to rdp->gp_seq. <<
165 */ <<
166 struct rcu_snap_record { <<
167 unsigned long gp_seq; /* Tra <<
168 u64 cputime_irq; /* Acc <<
169 u64 cputime_softirq;/* Acc <<
170 u64 cputime_system; /* Acc <<
171 unsigned long nr_hardirqs; /* Acc <<
172 unsigned int nr_softirqs; /* Acc <<
173 unsigned long long nr_csw; /* Acc <<
174 unsigned long jiffies; /* Tra <<
175 }; <<
176 <<
177 /* Per-CPU data for read-copy update. */ 150 /* Per-CPU data for read-copy update. */
178 struct rcu_data { 151 struct rcu_data {
179 /* 1) quiescent-state and grace-period 152 /* 1) quiescent-state and grace-period handling : */
180 unsigned long gp_seq; /* Tra 153 unsigned long gp_seq; /* Track rsp->gp_seq counter. */
181 unsigned long gp_seq_needed; /* Tra 154 unsigned long gp_seq_needed; /* Track furthest future GP request. */
182 union rcu_noqs cpu_no_qs; /* No 155 union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
183 bool core_needs_qs; /* Cor !! 156 bool core_needs_qs; /* Core waits for quiesc state. */
184 bool beenonline; /* CPU 157 bool beenonline; /* CPU online at least once. */
185 bool gpwrap; /* Pos 158 bool gpwrap; /* Possible ->gp_seq wrap. */
>> 159 bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */
186 bool cpu_started; /* RCU 160 bool cpu_started; /* RCU watching this onlining CPU. */
187 struct rcu_node *mynode; /* Thi 161 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
188 unsigned long grpmask; /* Mas 162 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
189 unsigned long ticks_this_gp; /* The 163 unsigned long ticks_this_gp; /* The number of scheduling-clock */
190 /* ti 164 /* ticks this CPU has handled */
191 /* du 165 /* during and after the last grace */
192 /* per 166 /* period it is aware of. */
193 struct irq_work defer_qs_iw; /* Obt 167 struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
194 bool defer_qs_iw_pending; /* Sch 168 bool defer_qs_iw_pending; /* Scheduler attention pending? */
195 struct work_struct strict_work; /* Sch 169 struct work_struct strict_work; /* Schedule readers for strict GPs. */
196 170
197 /* 2) batch handling */ 171 /* 2) batch handling */
198 struct rcu_segcblist cblist; /* Seg 172 struct rcu_segcblist cblist; /* Segmented callback list, with */
199 /* dif 173 /* different callbacks waiting for */
200 /* dif 174 /* different grace periods. */
201 long qlen_last_fqs_check; 175 long qlen_last_fqs_check;
202 /* qle 176 /* qlen at last check for QS forcing */
203 unsigned long n_cbs_invoked; /* # c 177 unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
204 unsigned long n_force_qs_snap; 178 unsigned long n_force_qs_snap;
205 /* did 179 /* did other CPU force QS recently? */
206 long blimit; /* Upp 180 long blimit; /* Upper limit on a processed batch */
207 181
208 /* 3) dynticks interface. */ 182 /* 3) dynticks interface. */
209 int watching_snap; /* Per !! 183 int dynticks_snap; /* Per-GP tracking for dynticks. */
>> 184 long dynticks_nesting; /* Track process nesting level. */
>> 185 long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
>> 186 atomic_t dynticks; /* Even value for idle, else odd. */
210 bool rcu_need_heavy_qs; /* GP 187 bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
211 bool rcu_urgent_qs; /* GP 188 bool rcu_urgent_qs; /* GP old need light quiescent state. */
212 bool rcu_forced_tick; /* For 189 bool rcu_forced_tick; /* Forced tick to provide QS. */
213 bool rcu_forced_tick_exp; /* . 190 bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
>> 191 #ifdef CONFIG_RCU_FAST_NO_HZ
>> 192 unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */
>> 193 unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */
>> 194 int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
>> 195 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
214 196
215 /* 4) rcu_barrier(), OOM callbacks, an 197 /* 4) rcu_barrier(), OOM callbacks, and expediting. */
216 unsigned long barrier_seq_snap; /* Sna <<
217 struct rcu_head barrier_head; 198 struct rcu_head barrier_head;
218 int exp_watching_snap; /* Dou !! 199 int exp_dynticks_snap; /* Double-check need for IPI. */
219 200
220 /* 5) Callback offloading. */ 201 /* 5) Callback offloading. */
221 #ifdef CONFIG_RCU_NOCB_CPU 202 #ifdef CONFIG_RCU_NOCB_CPU
222 struct swait_queue_head nocb_cb_wq; /* 203 struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
223 struct swait_queue_head nocb_state_wq; 204 struct swait_queue_head nocb_state_wq; /* For offloading state changes */
224 struct task_struct *nocb_gp_kthread; 205 struct task_struct *nocb_gp_kthread;
225 raw_spinlock_t nocb_lock; /* Gua 206 raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
>> 207 atomic_t nocb_lock_contended; /* Contention experienced. */
226 int nocb_defer_wakeup; /* Def 208 int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
227 struct timer_list nocb_timer; /* Enf 209 struct timer_list nocb_timer; /* Enforce finite deferral. */
228 unsigned long nocb_gp_adv_time; /* Las 210 unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
229 struct mutex nocb_gp_kthread_mutex; /* <<
230 /* <<
231 211
232 /* The following fields are used by ca 212 /* The following fields are used by call_rcu, hence own cacheline. */
233 raw_spinlock_t nocb_bypass_lock ____ca 213 raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
234 struct rcu_cblist nocb_bypass; /* Loc 214 struct rcu_cblist nocb_bypass; /* Lock-contention-bypass CB list. */
235 unsigned long nocb_bypass_first; /* Ti 215 unsigned long nocb_bypass_first; /* Time (jiffies) of first enqueue. */
236 unsigned long nocb_nobypass_last; /* L 216 unsigned long nocb_nobypass_last; /* Last ->cblist enqueue (jiffies). */
237 int nocb_nobypass_count; /* # - 217 int nocb_nobypass_count; /* # ->cblist enqueues at ^^^ time. */
238 218
239 /* The following fields are used by GP 219 /* The following fields are used by GP kthread, hence own cacheline. */
240 raw_spinlock_t nocb_gp_lock ____cachel 220 raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
>> 221 struct timer_list nocb_bypass_timer; /* Force nocb_bypass flush. */
241 u8 nocb_gp_sleep; /* Is 222 u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
242 u8 nocb_gp_bypass; /* Fou 223 u8 nocb_gp_bypass; /* Found a bypass on last scan? */
243 u8 nocb_gp_gp; /* GP 224 u8 nocb_gp_gp; /* GP to wait for on last scan? */
244 unsigned long nocb_gp_seq; /* If 225 unsigned long nocb_gp_seq; /* If so, ->gp_seq to wait for. */
245 unsigned long nocb_gp_loops; /* # p 226 unsigned long nocb_gp_loops; /* # passes through wait code. */
246 struct swait_queue_head nocb_gp_wq; /* 227 struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
247 bool nocb_cb_sleep; /* Is 228 bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
248 struct task_struct *nocb_cb_kthread; 229 struct task_struct *nocb_cb_kthread;
249 struct list_head nocb_head_rdp; /* !! 230 struct rcu_data *nocb_next_cb_rdp;
250 * Hea !! 231 /* Next rcu_data in wakeup chain. */
251 * if <<
252 */ <<
253 struct list_head nocb_entry_rdp; /* rc <<
254 struct rcu_data *nocb_toggling_rdp; /* <<
255 232
256 /* The following fields are used by CB 233 /* The following fields are used by CB kthread, hence new cacheline. */
257 struct rcu_data *nocb_gp_rdp ____cache 234 struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
258 /* GP 235 /* GP rdp takes GP-end wakeups. */
259 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ 236 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
260 237
261 /* 6) RCU priority boosting. */ 238 /* 6) RCU priority boosting. */
262 struct task_struct *rcu_cpu_kthread_ta 239 struct task_struct *rcu_cpu_kthread_task;
263 /* rcu 240 /* rcuc per-CPU kthread or NULL. */
264 unsigned int rcu_cpu_kthread_status; 241 unsigned int rcu_cpu_kthread_status;
265 char rcu_cpu_has_work; 242 char rcu_cpu_has_work;
266 unsigned long rcuc_activity; <<
267 243
268 /* 7) Diagnostic data, including RCU C 244 /* 7) Diagnostic data, including RCU CPU stall warnings. */
269 unsigned int softirq_snap; /* Sna 245 unsigned int softirq_snap; /* Snapshot of softirq activity. */
270 /* ->rcu_iw* fields protected by leaf 246 /* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
271 struct irq_work rcu_iw; /* Che 247 struct irq_work rcu_iw; /* Check for non-irq activity. */
272 bool rcu_iw_pending; /* Is 248 bool rcu_iw_pending; /* Is ->rcu_iw pending? */
273 unsigned long rcu_iw_gp_seq; /* ->g 249 unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
274 unsigned long rcu_ofl_gp_seq; /* ->g 250 unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */
275 short rcu_ofl_gp_state; /* ->g !! 251 short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */
276 unsigned long rcu_onl_gp_seq; /* ->g 252 unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
277 short rcu_onl_gp_state; /* ->g !! 253 short rcu_onl_gp_flags; /* ->gp_flags at last online. */
278 unsigned long last_fqs_resched; /* Tim 254 unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
279 unsigned long last_sched_clock; /* Jif <<
280 struct rcu_snap_record snap_record; /* <<
281 /* <<
282 255
283 long lazy_len; /* Len <<
284 int cpu; 256 int cpu;
285 }; 257 };
286 258
287 /* Values for nocb_defer_wakeup field in struc 259 /* Values for nocb_defer_wakeup field in struct rcu_data. */
>> 260 #define RCU_NOCB_WAKE_OFF -1
288 #define RCU_NOCB_WAKE_NOT 0 261 #define RCU_NOCB_WAKE_NOT 0
289 #define RCU_NOCB_WAKE_BYPASS 1 !! 262 #define RCU_NOCB_WAKE 1
290 #define RCU_NOCB_WAKE_LAZY 2 !! 263 #define RCU_NOCB_WAKE_FORCE 2
291 #define RCU_NOCB_WAKE 3 <<
292 #define RCU_NOCB_WAKE_FORCE 4 <<
293 264
294 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 2 265 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
295 /* For 266 /* For jiffies_till_first_fqs and */
296 /* an 267 /* and jiffies_till_next_fqs. */
297 268
298 #define RCU_JIFFIES_FQS_DIV 256 /* Ver 269 #define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
299 /* de 270 /* delay between bouts of */
300 /* qu 271 /* quiescent-state forcing. */
301 272
302 #define RCU_STALL_RAT_DELAY 2 /* All 273 #define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
303 /* at 274 /* at least one scheduling clock */
304 /* ir 275 /* irq before ratting on them. */
305 276
306 #define rcu_wait(cond) 277 #define rcu_wait(cond) \
307 do { 278 do { \
308 for (;;) { 279 for (;;) { \
309 set_current_state(TASK_INTERRU 280 set_current_state(TASK_INTERRUPTIBLE); \
310 if (cond) 281 if (cond) \
311 break; 282 break; \
312 schedule(); 283 schedule(); \
313 } 284 } \
314 __set_current_state(TASK_RUNNING); 285 __set_current_state(TASK_RUNNING); \
315 } while (0) 286 } while (0)
316 287
317 /* 288 /*
318 * A max threshold for synchronize_rcu() users <<
319 * awaken directly by the rcu_gp_kthread(). Le <<
320 * deferred to the main worker. <<
321 */ <<
322 #define SR_MAX_USERS_WAKE_FROM_GP 5 <<
323 #define SR_NORMAL_GP_WAIT_HEAD_MAX 5 <<
324 <<
325 struct sr_wait_node { <<
326 atomic_t inuse; <<
327 struct llist_node node; <<
328 }; <<
329 <<
330 /* <<
331 * RCU global state, including node hierarchy. 289 * RCU global state, including node hierarchy. This hierarchy is
332 * represented in "heap" form in a dense array 290 * represented in "heap" form in a dense array. The root (first level)
333 * of the hierarchy is in ->node[0] (reference 291 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
334 * level in ->node[1] through ->node[m] (->nod 292 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
335 * and the third level in ->node[m+1] and foll 293 * and the third level in ->node[m+1] and following (->node[m+1] referenced
336 * by ->level[2]). The number of levels is de 294 * by ->level[2]). The number of levels is determined by the number of
337 * CPUs and by CONFIG_RCU_FANOUT. Small syste 295 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
338 * consisting of a single rcu_node. 296 * consisting of a single rcu_node.
339 */ 297 */
340 struct rcu_state { 298 struct rcu_state {
341 struct rcu_node node[NUM_RCU_NODES]; 299 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
342 struct rcu_node *level[RCU_NUM_LVLS + 300 struct rcu_node *level[RCU_NUM_LVLS + 1];
343 301 /* Hierarchy levels (+1 to */
344 302 /* shut bogus gcc warning) */
345 int ncpus; 303 int ncpus; /* # CPUs seen so far. */
346 int n_online_cpus; 304 int n_online_cpus; /* # CPUs online for RCU. */
347 305
348 /* The following fields are guarded by 306 /* The following fields are guarded by the root rcu_node's lock. */
349 307
350 unsigned long gp_seq ____cacheline_int !! 308 u8 boost ____cacheline_internodealigned_in_smp;
351 !! 309 /* Subject to priority boost. */
>> 310 unsigned long gp_seq; /* Grace-period sequence #. */
352 unsigned long gp_max; 311 unsigned long gp_max; /* Maximum GP duration in */
353 312 /* jiffies. */
354 struct task_struct *gp_kthread; 313 struct task_struct *gp_kthread; /* Task for grace periods. */
355 struct swait_queue_head gp_wq; 314 struct swait_queue_head gp_wq; /* Where GP task waits. */
356 short gp_flags; 315 short gp_flags; /* Commands for GP task. */
357 short gp_state; 316 short gp_state; /* GP kthread sleep state. */
358 unsigned long gp_wake_time; 317 unsigned long gp_wake_time; /* Last GP kthread wake. */
359 unsigned long gp_wake_seq; 318 unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
360 unsigned long gp_seq_polled; <<
361 unsigned long gp_seq_polled_snap; <<
362 unsigned long gp_seq_polled_exp_snap; <<
363 319
364 /* End of fields guarded by root rcu_n 320 /* End of fields guarded by root rcu_node's lock. */
365 321
366 struct mutex barrier_mutex; 322 struct mutex barrier_mutex; /* Guards barrier fields. */
367 atomic_t barrier_cpu_count; 323 atomic_t barrier_cpu_count; /* # CPUs waiting on. */
368 struct completion barrier_completion; 324 struct completion barrier_completion; /* Wake at barrier end. */
369 unsigned long barrier_sequence; 325 unsigned long barrier_sequence; /* ++ at start and end of */
370 326 /* rcu_barrier(). */
371 /* End of fields guarded by barrier_mu 327 /* End of fields guarded by barrier_mutex. */
372 328
373 raw_spinlock_t barrier_lock; <<
374 <<
375 struct mutex exp_mutex; 329 struct mutex exp_mutex; /* Serialize expedited GP. */
376 struct mutex exp_wake_mutex; 330 struct mutex exp_wake_mutex; /* Serialize wakeup. */
377 unsigned long expedited_sequence; 331 unsigned long expedited_sequence; /* Take a ticket. */
378 atomic_t expedited_need_qs; 332 atomic_t expedited_need_qs; /* # CPUs left to check in. */
379 struct swait_queue_head expedited_wq; 333 struct swait_queue_head expedited_wq; /* Wait for check-ins. */
380 int ncpus_snap; 334 int ncpus_snap; /* # CPUs seen last time. */
381 u8 cbovld; 335 u8 cbovld; /* Callback overload now? */
382 u8 cbovldnext; 336 u8 cbovldnext; /* ^ ^ next time? */
383 337
384 unsigned long jiffies_force_qs; 338 unsigned long jiffies_force_qs; /* Time at which to invoke */
385 339 /* force_quiescent_state(). */
386 unsigned long jiffies_kick_kthreads; 340 unsigned long jiffies_kick_kthreads; /* Time at which to kick */
387 341 /* kthreads, if configured. */
388 unsigned long n_force_qs; 342 unsigned long n_force_qs; /* Number of calls to */
389 343 /* force_quiescent_state(). */
390 unsigned long gp_start; 344 unsigned long gp_start; /* Time at which GP started, */
391 345 /* but in jiffies. */
392 unsigned long gp_end; 346 unsigned long gp_end; /* Time last GP ended, again */
393 347 /* in jiffies. */
394 unsigned long gp_activity; 348 unsigned long gp_activity; /* Time of last GP kthread */
395 349 /* activity in jiffies. */
396 unsigned long gp_req_activity; 350 unsigned long gp_req_activity; /* Time of last GP request */
397 351 /* in jiffies. */
398 unsigned long jiffies_stall; 352 unsigned long jiffies_stall; /* Time at which to check */
399 353 /* for CPU stalls. */
400 int nr_fqs_jiffies_stall; <<
401 <<
402 <<
403 <<
404 unsigned long jiffies_resched; 354 unsigned long jiffies_resched; /* Time at which to resched */
405 355 /* a reluctant CPU. */
406 unsigned long n_force_qs_gpstart; 356 unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
407 357 /* GP start. */
408 const char *name; 358 const char *name; /* Name of structure. */
409 char abbr; 359 char abbr; /* Abbreviated name. */
410 360
411 arch_spinlock_t ofl_lock ____cacheline !! 361 raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
412 362 /* Synchronize offline with */
413 363 /* GP pre-initialization. */
414 <<
415 /* synchronize_rcu() part. */ <<
416 struct llist_head srs_next; /* req <<
417 struct llist_node *srs_wait_tail; /* w <<
418 struct llist_node *srs_done_tail; /* r <<
419 struct sr_wait_node srs_wait_nodes[SR_ <<
420 struct work_struct srs_cleanup_work; <<
421 atomic_t srs_cleanups_pending; /* srs <<
422 <<
423 #ifdef CONFIG_RCU_NOCB_CPU <<
424 struct mutex nocb_mutex; <<
425 int nocb_is_setup; <<
426 #endif <<
427 }; 364 };
428 365
429 /* Values for rcu_state structure's gp_flags f 366 /* Values for rcu_state structure's gp_flags field. */
430 #define RCU_GP_FLAG_INIT 0x1 /* Need grace- 367 #define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
431 #define RCU_GP_FLAG_FQS 0x2 /* Need grace- 368 #define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
432 #define RCU_GP_FLAG_OVLD 0x4 /* Experiencin 369 #define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
433 370
434 /* Values for rcu_state structure's gp_state f 371 /* Values for rcu_state structure's gp_state field. */
435 #define RCU_GP_IDLE 0 /* Initial sta 372 #define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
436 #define RCU_GP_WAIT_GPS 1 /* Wait for gr 373 #define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
437 #define RCU_GP_DONE_GPS 2 /* Wait done f 374 #define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
438 #define RCU_GP_ONOFF 3 /* Grace-perio 375 #define RCU_GP_ONOFF 3 /* Grace-period initialization hotplug. */
439 #define RCU_GP_INIT 4 /* Grace-perio 376 #define RCU_GP_INIT 4 /* Grace-period initialization. */
440 #define RCU_GP_WAIT_FQS 5 /* Wait for fo 377 #define RCU_GP_WAIT_FQS 5 /* Wait for force-quiescent-state time. */
441 #define RCU_GP_DOING_FQS 6 /* Wait done f 378 #define RCU_GP_DOING_FQS 6 /* Wait done for force-quiescent-state time. */
442 #define RCU_GP_CLEANUP 7 /* Grace-perio 379 #define RCU_GP_CLEANUP 7 /* Grace-period cleanup started. */
443 #define RCU_GP_CLEANED 8 /* Grace-perio 380 #define RCU_GP_CLEANED 8 /* Grace-period cleanup complete. */
444 381
445 /* 382 /*
446 * In order to export the rcu_state name to th 383 * In order to export the rcu_state name to the tracing tools, it
447 * needs to be added in the __tracepoint_strin 384 * needs to be added in the __tracepoint_string section.
448 * This requires defining a separate variable 385 * This requires defining a separate variable tp_<sname>_varname
449 * that points to the string being used, and t 386 * that points to the string being used, and this will allow
450 * the tracing userspace tools to be able to d 387 * the tracing userspace tools to be able to decipher the string
451 * address to the matching string. 388 * address to the matching string.
452 */ 389 */
453 #ifdef CONFIG_PREEMPT_RCU 390 #ifdef CONFIG_PREEMPT_RCU
454 #define RCU_ABBR 'p' 391 #define RCU_ABBR 'p'
455 #define RCU_NAME_RAW "rcu_preempt" 392 #define RCU_NAME_RAW "rcu_preempt"
456 #else /* #ifdef CONFIG_PREEMPT_RCU */ 393 #else /* #ifdef CONFIG_PREEMPT_RCU */
457 #define RCU_ABBR 's' 394 #define RCU_ABBR 's'
458 #define RCU_NAME_RAW "rcu_sched" 395 #define RCU_NAME_RAW "rcu_sched"
459 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ 396 #endif /* #else #ifdef CONFIG_PREEMPT_RCU */
460 #ifndef CONFIG_TRACING 397 #ifndef CONFIG_TRACING
461 #define RCU_NAME RCU_NAME_RAW 398 #define RCU_NAME RCU_NAME_RAW
462 #else /* #ifdef CONFIG_TRACING */ 399 #else /* #ifdef CONFIG_TRACING */
463 static char rcu_name[] = RCU_NAME_RAW; 400 static char rcu_name[] = RCU_NAME_RAW;
464 static const char *tp_rcu_varname __used __tra 401 static const char *tp_rcu_varname __used __tracepoint_string = rcu_name;
465 #define RCU_NAME rcu_name 402 #define RCU_NAME rcu_name
466 #endif /* #else #ifdef CONFIG_TRACING */ 403 #endif /* #else #ifdef CONFIG_TRACING */
467 404
468 /* Forward declarations for tree_plugin.h */ 405 /* Forward declarations for tree_plugin.h */
469 static void rcu_bootup_announce(void); 406 static void rcu_bootup_announce(void);
470 static void rcu_qs(void); 407 static void rcu_qs(void);
471 static int rcu_preempt_blocked_readers_cgp(str 408 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
472 #ifdef CONFIG_HOTPLUG_CPU 409 #ifdef CONFIG_HOTPLUG_CPU
473 static bool rcu_preempt_has_tasks(struct rcu_n 410 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
474 #endif /* #ifdef CONFIG_HOTPLUG_CPU */ 411 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
475 static int rcu_print_task_exp_stall(struct rcu 412 static int rcu_print_task_exp_stall(struct rcu_node *rnp);
476 static void rcu_preempt_check_blocked_tasks(st 413 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
477 static void rcu_flavor_sched_clock_irq(int use 414 static void rcu_flavor_sched_clock_irq(int user);
478 static void dump_blkd_tasks(struct rcu_node *r 415 static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
479 static void rcu_initiate_boost(struct rcu_node 416 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
480 static void rcu_preempt_boost_start_gp(struct 417 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
481 static bool rcu_is_callbacks_kthread(struct rc !! 418 static bool rcu_is_callbacks_kthread(void);
482 static void rcu_cpu_kthread_setup(unsigned int 419 static void rcu_cpu_kthread_setup(unsigned int cpu);
483 static void rcu_spawn_one_boost_kthread(struct !! 420 static void __init rcu_spawn_boost_kthreads(void);
>> 421 static void rcu_prepare_kthreads(int cpu);
>> 422 static void rcu_cleanup_after_idle(void);
>> 423 static void rcu_prepare_for_idle(void);
484 static bool rcu_preempt_has_tasks(struct rcu_n 424 static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
485 static bool rcu_preempt_need_deferred_qs(struc 425 static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
>> 426 static void rcu_preempt_deferred_qs(struct task_struct *t);
486 static void zero_cpu_stall_ticks(struct rcu_da 427 static void zero_cpu_stall_ticks(struct rcu_data *rdp);
487 static struct swait_queue_head *rcu_nocb_gp_ge 428 static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
488 static void rcu_nocb_gp_cleanup(struct swait_q 429 static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
489 static void rcu_init_one_nocb(struct rcu_node 430 static void rcu_init_one_nocb(struct rcu_node *rnp);
490 static bool wake_nocb_gp(struct rcu_data *rdp, <<
491 static bool rcu_nocb_flush_bypass(struct rcu_d 431 static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
492 unsigned lon !! 432 unsigned long j);
493 static void call_rcu_nocb(struct rcu_data *rdp !! 433 static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
494 rcu_callback_t func, !! 434 bool *was_alldone, unsigned long flags);
495 static void __maybe_unused __call_rcu_nocb_wak !! 435 static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
496 !! 436 unsigned long flags);
497 static int rcu_nocb_need_deferred_wakeup(struc !! 437 static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
498 static bool do_nocb_deferred_wakeup(struct rcu 438 static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
499 static void rcu_boot_init_nocb_percpu_data(str 439 static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
500 static void rcu_spawn_cpu_nocb_kthread(int cpu 440 static void rcu_spawn_cpu_nocb_kthread(int cpu);
>> 441 static void __init rcu_spawn_nocb_kthreads(void);
501 static void show_rcu_nocb_state(struct rcu_dat 442 static void show_rcu_nocb_state(struct rcu_data *rdp);
502 static void rcu_nocb_lock(struct rcu_data *rdp 443 static void rcu_nocb_lock(struct rcu_data *rdp);
503 static void rcu_nocb_unlock(struct rcu_data *r 444 static void rcu_nocb_unlock(struct rcu_data *rdp);
504 static void rcu_nocb_unlock_irqrestore(struct 445 static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
505 unsigne 446 unsigned long flags);
506 static void rcu_lockdep_assert_cblist_protecte 447 static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
507 #ifdef CONFIG_RCU_NOCB_CPU 448 #ifdef CONFIG_RCU_NOCB_CPU
508 static void __init rcu_organize_nocb_kthreads( 449 static void __init rcu_organize_nocb_kthreads(void);
509 !! 450 #define rcu_nocb_lock_irqsave(rdp, flags) \
510 /* !! 451 do { \
511 * Disable IRQs before checking offloaded stat !! 452 if (!rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
512 * locking is safe against concurrent de-offlo !! 453 local_irq_save(flags); \
513 */ !! 454 else \
514 #define rcu_nocb_lock_irqsave(rdp, flags) !! 455 raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags)); \
515 do { <<
516 local_irq_save(flags); <<
517 if (rcu_segcblist_is_offloaded(&(rdp)- <<
518 raw_spin_lock(&(rdp)->nocb_loc <<
519 } while (0) 456 } while (0)
520 #else /* #ifdef CONFIG_RCU_NOCB_CPU */ 457 #else /* #ifdef CONFIG_RCU_NOCB_CPU */
521 #define rcu_nocb_lock_irqsave(rdp, flags) loca 458 #define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
522 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ 459 #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
523 460
524 static void rcu_bind_gp_kthread(void); 461 static void rcu_bind_gp_kthread(void);
525 static bool rcu_nohz_full_cpu(void); 462 static bool rcu_nohz_full_cpu(void);
>> 463 static void rcu_dynticks_task_enter(void);
>> 464 static void rcu_dynticks_task_exit(void);
>> 465 static void rcu_dynticks_task_trace_enter(void);
>> 466 static void rcu_dynticks_task_trace_exit(void);
526 467
527 /* Forward declarations for tree_stall.h */ 468 /* Forward declarations for tree_stall.h */
528 static void record_gp_stall_check_time(void); 469 static void record_gp_stall_check_time(void);
529 static void rcu_iw_handler(struct irq_work *iw 470 static void rcu_iw_handler(struct irq_work *iwp);
530 static void check_cpu_stall(struct rcu_data *r 471 static void check_cpu_stall(struct rcu_data *rdp);
531 static void rcu_check_gp_start_stall(struct rc 472 static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
532 const uns 473 const unsigned long gpssdelay);
533 <<
534 /* Forward declarations for tree_exp.h. */ <<
535 static void sync_rcu_do_polled_gp(struct work_ <<
536 474
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