Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
| 18 | * Copyright IBM Corporation, 2008 |
| 19 | * |
| 20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| 21 | * Manfred Spraul <manfred@colorfullife.com> |
| 22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version |
| 23 | * |
| 24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| 25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 26 | * |
| 27 | * For detailed explanation of Read-Copy Update mechanism see - |
| 28 | * Documentation/RCU |
| 29 | */ |
| 30 | #include <linux/types.h> |
| 31 | #include <linux/kernel.h> |
| 32 | #include <linux/init.h> |
| 33 | #include <linux/spinlock.h> |
| 34 | #include <linux/smp.h> |
| 35 | #include <linux/rcupdate.h> |
| 36 | #include <linux/interrupt.h> |
| 37 | #include <linux/sched.h> |
| 38 | #include <asm/atomic.h> |
| 39 | #include <linux/bitops.h> |
| 40 | #include <linux/module.h> |
| 41 | #include <linux/completion.h> |
| 42 | #include <linux/moduleparam.h> |
| 43 | #include <linux/percpu.h> |
| 44 | #include <linux/notifier.h> |
| 45 | #include <linux/cpu.h> |
| 46 | #include <linux/mutex.h> |
| 47 | #include <linux/time.h> |
| 48 | |
Paul E. McKenney | 9f77da9 | 2009-08-22 13:56:45 -0700 | [diff] [blame] | 49 | #include "rcutree.h" |
| 50 | |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 51 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 52 | static struct lock_class_key rcu_lock_key; |
| 53 | struct lockdep_map rcu_lock_map = |
| 54 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); |
| 55 | EXPORT_SYMBOL_GPL(rcu_lock_map); |
| 56 | #endif |
| 57 | |
| 58 | /* Data structures. */ |
| 59 | |
| 60 | #define RCU_STATE_INITIALIZER(name) { \ |
| 61 | .level = { &name.node[0] }, \ |
| 62 | .levelcnt = { \ |
| 63 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ |
| 64 | NUM_RCU_LVL_1, \ |
| 65 | NUM_RCU_LVL_2, \ |
| 66 | NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \ |
| 67 | }, \ |
| 68 | .signaled = RCU_SIGNAL_INIT, \ |
| 69 | .gpnum = -300, \ |
| 70 | .completed = -300, \ |
| 71 | .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \ |
| 72 | .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \ |
| 73 | .n_force_qs = 0, \ |
| 74 | .n_force_qs_ngp = 0, \ |
| 75 | } |
| 76 | |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 77 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
| 78 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 79 | |
Ingo Molnar | 6258c4f | 2009-03-25 16:42:24 +0100 | [diff] [blame] | 80 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
| 81 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 82 | |
| 83 | /* |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 84 | * Note a quiescent state. Because we do not need to know |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 85 | * how many quiescent states passed, just if there was at least |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 86 | * one since the start of the grace period, this just sets a flag. |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 87 | */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 88 | void rcu_sched_qs(int cpu) |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 89 | { |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 90 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 91 | rdp->passed_quiesc = 1; |
| 92 | rdp->passed_quiesc_completed = rdp->completed; |
| 93 | } |
| 94 | |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 95 | void rcu_bh_qs(int cpu) |
Ingo Molnar | b1f77b0 | 2009-03-13 03:20:49 +0100 | [diff] [blame] | 96 | { |
| 97 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
| 98 | rdp->passed_quiesc = 1; |
| 99 | rdp->passed_quiesc_completed = rdp->completed; |
| 100 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 101 | |
| 102 | #ifdef CONFIG_NO_HZ |
Paul E. McKenney | 90a4d2c | 2009-01-04 11:41:11 -0800 | [diff] [blame] | 103 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
| 104 | .dynticks_nesting = 1, |
| 105 | .dynticks = 1, |
| 106 | }; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 107 | #endif /* #ifdef CONFIG_NO_HZ */ |
| 108 | |
| 109 | static int blimit = 10; /* Maximum callbacks per softirq. */ |
| 110 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
| 111 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ |
| 112 | |
| 113 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
| 114 | |
| 115 | /* |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 116 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
| 117 | */ |
| 118 | long rcu_batches_completed_sched(void) |
| 119 | { |
| 120 | return rcu_sched_state.completed; |
| 121 | } |
| 122 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
| 123 | |
| 124 | /* |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 125 | * Return the number of RCU batches processed thus far for debug & stats. |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 126 | * @@@ placeholder, maps to rcu_batches_completed_sched(). |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 127 | */ |
| 128 | long rcu_batches_completed(void) |
| 129 | { |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 130 | return rcu_batches_completed_sched(); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 131 | } |
| 132 | EXPORT_SYMBOL_GPL(rcu_batches_completed); |
| 133 | |
| 134 | /* |
| 135 | * Return the number of RCU BH batches processed thus far for debug & stats. |
| 136 | */ |
| 137 | long rcu_batches_completed_bh(void) |
| 138 | { |
| 139 | return rcu_bh_state.completed; |
| 140 | } |
| 141 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
| 142 | |
| 143 | /* |
| 144 | * Does the CPU have callbacks ready to be invoked? |
| 145 | */ |
| 146 | static int |
| 147 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
| 148 | { |
| 149 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; |
| 150 | } |
| 151 | |
| 152 | /* |
| 153 | * Does the current CPU require a yet-as-unscheduled grace period? |
| 154 | */ |
| 155 | static int |
| 156 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
| 157 | { |
| 158 | /* ACCESS_ONCE() because we are accessing outside of lock. */ |
| 159 | return *rdp->nxttail[RCU_DONE_TAIL] && |
| 160 | ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum); |
| 161 | } |
| 162 | |
| 163 | /* |
| 164 | * Return the root node of the specified rcu_state structure. |
| 165 | */ |
| 166 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
| 167 | { |
| 168 | return &rsp->node[0]; |
| 169 | } |
| 170 | |
| 171 | #ifdef CONFIG_SMP |
| 172 | |
| 173 | /* |
| 174 | * If the specified CPU is offline, tell the caller that it is in |
| 175 | * a quiescent state. Otherwise, whack it with a reschedule IPI. |
| 176 | * Grace periods can end up waiting on an offline CPU when that |
| 177 | * CPU is in the process of coming online -- it will be added to the |
| 178 | * rcu_node bitmasks before it actually makes it online. The same thing |
| 179 | * can happen while a CPU is in the process of coming online. Because this |
| 180 | * race is quite rare, we check for it after detecting that the grace |
| 181 | * period has been delayed rather than checking each and every CPU |
| 182 | * each and every time we start a new grace period. |
| 183 | */ |
| 184 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) |
| 185 | { |
| 186 | /* |
| 187 | * If the CPU is offline, it is in a quiescent state. We can |
| 188 | * trust its state not to change because interrupts are disabled. |
| 189 | */ |
| 190 | if (cpu_is_offline(rdp->cpu)) { |
| 191 | rdp->offline_fqs++; |
| 192 | return 1; |
| 193 | } |
| 194 | |
| 195 | /* The CPU is online, so send it a reschedule IPI. */ |
| 196 | if (rdp->cpu != smp_processor_id()) |
| 197 | smp_send_reschedule(rdp->cpu); |
| 198 | else |
| 199 | set_need_resched(); |
| 200 | rdp->resched_ipi++; |
| 201 | return 0; |
| 202 | } |
| 203 | |
| 204 | #endif /* #ifdef CONFIG_SMP */ |
| 205 | |
| 206 | #ifdef CONFIG_NO_HZ |
| 207 | static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5); |
| 208 | |
| 209 | /** |
| 210 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz |
| 211 | * |
| 212 | * Enter nohz mode, in other words, -leave- the mode in which RCU |
| 213 | * read-side critical sections can occur. (Though RCU read-side |
| 214 | * critical sections can occur in irq handlers in nohz mode, a possibility |
| 215 | * handled by rcu_irq_enter() and rcu_irq_exit()). |
| 216 | */ |
| 217 | void rcu_enter_nohz(void) |
| 218 | { |
| 219 | unsigned long flags; |
| 220 | struct rcu_dynticks *rdtp; |
| 221 | |
| 222 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| 223 | local_irq_save(flags); |
| 224 | rdtp = &__get_cpu_var(rcu_dynticks); |
| 225 | rdtp->dynticks++; |
| 226 | rdtp->dynticks_nesting--; |
| 227 | WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); |
| 228 | local_irq_restore(flags); |
| 229 | } |
| 230 | |
| 231 | /* |
| 232 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz |
| 233 | * |
| 234 | * Exit nohz mode, in other words, -enter- the mode in which RCU |
| 235 | * read-side critical sections normally occur. |
| 236 | */ |
| 237 | void rcu_exit_nohz(void) |
| 238 | { |
| 239 | unsigned long flags; |
| 240 | struct rcu_dynticks *rdtp; |
| 241 | |
| 242 | local_irq_save(flags); |
| 243 | rdtp = &__get_cpu_var(rcu_dynticks); |
| 244 | rdtp->dynticks++; |
| 245 | rdtp->dynticks_nesting++; |
| 246 | WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); |
| 247 | local_irq_restore(flags); |
| 248 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| 249 | } |
| 250 | |
| 251 | /** |
| 252 | * rcu_nmi_enter - inform RCU of entry to NMI context |
| 253 | * |
| 254 | * If the CPU was idle with dynamic ticks active, and there is no |
| 255 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
| 256 | * RCU grace-period handling know that the CPU is active. |
| 257 | */ |
| 258 | void rcu_nmi_enter(void) |
| 259 | { |
| 260 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 261 | |
| 262 | if (rdtp->dynticks & 0x1) |
| 263 | return; |
| 264 | rdtp->dynticks_nmi++; |
| 265 | WARN_ON_RATELIMIT(!(rdtp->dynticks_nmi & 0x1), &rcu_rs); |
| 266 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| 267 | } |
| 268 | |
| 269 | /** |
| 270 | * rcu_nmi_exit - inform RCU of exit from NMI context |
| 271 | * |
| 272 | * If the CPU was idle with dynamic ticks active, and there is no |
| 273 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
| 274 | * RCU grace-period handling know that the CPU is no longer active. |
| 275 | */ |
| 276 | void rcu_nmi_exit(void) |
| 277 | { |
| 278 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 279 | |
| 280 | if (rdtp->dynticks & 0x1) |
| 281 | return; |
| 282 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| 283 | rdtp->dynticks_nmi++; |
| 284 | WARN_ON_RATELIMIT(rdtp->dynticks_nmi & 0x1, &rcu_rs); |
| 285 | } |
| 286 | |
| 287 | /** |
| 288 | * rcu_irq_enter - inform RCU of entry to hard irq context |
| 289 | * |
| 290 | * If the CPU was idle with dynamic ticks active, this updates the |
| 291 | * rdtp->dynticks to let the RCU handling know that the CPU is active. |
| 292 | */ |
| 293 | void rcu_irq_enter(void) |
| 294 | { |
| 295 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 296 | |
| 297 | if (rdtp->dynticks_nesting++) |
| 298 | return; |
| 299 | rdtp->dynticks++; |
| 300 | WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); |
| 301 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| 302 | } |
| 303 | |
| 304 | /** |
| 305 | * rcu_irq_exit - inform RCU of exit from hard irq context |
| 306 | * |
| 307 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks |
| 308 | * to put let the RCU handling be aware that the CPU is going back to idle |
| 309 | * with no ticks. |
| 310 | */ |
| 311 | void rcu_irq_exit(void) |
| 312 | { |
| 313 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 314 | |
| 315 | if (--rdtp->dynticks_nesting) |
| 316 | return; |
| 317 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| 318 | rdtp->dynticks++; |
| 319 | WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); |
| 320 | |
| 321 | /* If the interrupt queued a callback, get out of dyntick mode. */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 322 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 323 | __get_cpu_var(rcu_bh_data).nxtlist) |
| 324 | set_need_resched(); |
| 325 | } |
| 326 | |
| 327 | /* |
| 328 | * Record the specified "completed" value, which is later used to validate |
| 329 | * dynticks counter manipulations. Specify "rsp->completed - 1" to |
| 330 | * unconditionally invalidate any future dynticks manipulations (which is |
| 331 | * useful at the beginning of a grace period). |
| 332 | */ |
| 333 | static void dyntick_record_completed(struct rcu_state *rsp, long comp) |
| 334 | { |
| 335 | rsp->dynticks_completed = comp; |
| 336 | } |
| 337 | |
| 338 | #ifdef CONFIG_SMP |
| 339 | |
| 340 | /* |
| 341 | * Recall the previously recorded value of the completion for dynticks. |
| 342 | */ |
| 343 | static long dyntick_recall_completed(struct rcu_state *rsp) |
| 344 | { |
| 345 | return rsp->dynticks_completed; |
| 346 | } |
| 347 | |
| 348 | /* |
| 349 | * Snapshot the specified CPU's dynticks counter so that we can later |
| 350 | * credit them with an implicit quiescent state. Return 1 if this CPU |
| 351 | * is already in a quiescent state courtesy of dynticks idle mode. |
| 352 | */ |
| 353 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| 354 | { |
| 355 | int ret; |
| 356 | int snap; |
| 357 | int snap_nmi; |
| 358 | |
| 359 | snap = rdp->dynticks->dynticks; |
| 360 | snap_nmi = rdp->dynticks->dynticks_nmi; |
| 361 | smp_mb(); /* Order sampling of snap with end of grace period. */ |
| 362 | rdp->dynticks_snap = snap; |
| 363 | rdp->dynticks_nmi_snap = snap_nmi; |
| 364 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); |
| 365 | if (ret) |
| 366 | rdp->dynticks_fqs++; |
| 367 | return ret; |
| 368 | } |
| 369 | |
| 370 | /* |
| 371 | * Return true if the specified CPU has passed through a quiescent |
| 372 | * state by virtue of being in or having passed through an dynticks |
| 373 | * idle state since the last call to dyntick_save_progress_counter() |
| 374 | * for this same CPU. |
| 375 | */ |
| 376 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| 377 | { |
| 378 | long curr; |
| 379 | long curr_nmi; |
| 380 | long snap; |
| 381 | long snap_nmi; |
| 382 | |
| 383 | curr = rdp->dynticks->dynticks; |
| 384 | snap = rdp->dynticks_snap; |
| 385 | curr_nmi = rdp->dynticks->dynticks_nmi; |
| 386 | snap_nmi = rdp->dynticks_nmi_snap; |
| 387 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ |
| 388 | |
| 389 | /* |
| 390 | * If the CPU passed through or entered a dynticks idle phase with |
| 391 | * no active irq/NMI handlers, then we can safely pretend that the CPU |
| 392 | * already acknowledged the request to pass through a quiescent |
| 393 | * state. Either way, that CPU cannot possibly be in an RCU |
| 394 | * read-side critical section that started before the beginning |
| 395 | * of the current RCU grace period. |
| 396 | */ |
| 397 | if ((curr != snap || (curr & 0x1) == 0) && |
| 398 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { |
| 399 | rdp->dynticks_fqs++; |
| 400 | return 1; |
| 401 | } |
| 402 | |
| 403 | /* Go check for the CPU being offline. */ |
| 404 | return rcu_implicit_offline_qs(rdp); |
| 405 | } |
| 406 | |
| 407 | #endif /* #ifdef CONFIG_SMP */ |
| 408 | |
| 409 | #else /* #ifdef CONFIG_NO_HZ */ |
| 410 | |
| 411 | static void dyntick_record_completed(struct rcu_state *rsp, long comp) |
| 412 | { |
| 413 | } |
| 414 | |
| 415 | #ifdef CONFIG_SMP |
| 416 | |
| 417 | /* |
| 418 | * If there are no dynticks, then the only way that a CPU can passively |
| 419 | * be in a quiescent state is to be offline. Unlike dynticks idle, which |
| 420 | * is a point in time during the prior (already finished) grace period, |
| 421 | * an offline CPU is always in a quiescent state, and thus can be |
| 422 | * unconditionally applied. So just return the current value of completed. |
| 423 | */ |
| 424 | static long dyntick_recall_completed(struct rcu_state *rsp) |
| 425 | { |
| 426 | return rsp->completed; |
| 427 | } |
| 428 | |
| 429 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| 430 | { |
| 431 | return 0; |
| 432 | } |
| 433 | |
| 434 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| 435 | { |
| 436 | return rcu_implicit_offline_qs(rdp); |
| 437 | } |
| 438 | |
| 439 | #endif /* #ifdef CONFIG_SMP */ |
| 440 | |
| 441 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
| 442 | |
| 443 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| 444 | |
| 445 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
| 446 | { |
| 447 | rsp->gp_start = jiffies; |
| 448 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
| 449 | } |
| 450 | |
| 451 | static void print_other_cpu_stall(struct rcu_state *rsp) |
| 452 | { |
| 453 | int cpu; |
| 454 | long delta; |
| 455 | unsigned long flags; |
| 456 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 457 | struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1]; |
| 458 | struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES]; |
| 459 | |
| 460 | /* Only let one CPU complain about others per time interval. */ |
| 461 | |
| 462 | spin_lock_irqsave(&rnp->lock, flags); |
| 463 | delta = jiffies - rsp->jiffies_stall; |
| 464 | if (delta < RCU_STALL_RAT_DELAY || rsp->gpnum == rsp->completed) { |
| 465 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 466 | return; |
| 467 | } |
| 468 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| 469 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 470 | |
| 471 | /* OK, time to rat on our buddy... */ |
| 472 | |
| 473 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); |
| 474 | for (; rnp_cur < rnp_end; rnp_cur++) { |
| 475 | if (rnp_cur->qsmask == 0) |
| 476 | continue; |
| 477 | for (cpu = 0; cpu <= rnp_cur->grphi - rnp_cur->grplo; cpu++) |
| 478 | if (rnp_cur->qsmask & (1UL << cpu)) |
| 479 | printk(" %d", rnp_cur->grplo + cpu); |
| 480 | } |
| 481 | printk(" (detected by %d, t=%ld jiffies)\n", |
| 482 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
| 483 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
| 484 | } |
| 485 | |
| 486 | static void print_cpu_stall(struct rcu_state *rsp) |
| 487 | { |
| 488 | unsigned long flags; |
| 489 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 490 | |
| 491 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", |
| 492 | smp_processor_id(), jiffies - rsp->gp_start); |
| 493 | dump_stack(); |
| 494 | spin_lock_irqsave(&rnp->lock, flags); |
| 495 | if ((long)(jiffies - rsp->jiffies_stall) >= 0) |
| 496 | rsp->jiffies_stall = |
| 497 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| 498 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 499 | set_need_resched(); /* kick ourselves to get things going. */ |
| 500 | } |
| 501 | |
| 502 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| 503 | { |
| 504 | long delta; |
| 505 | struct rcu_node *rnp; |
| 506 | |
| 507 | delta = jiffies - rsp->jiffies_stall; |
| 508 | rnp = rdp->mynode; |
| 509 | if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { |
| 510 | |
| 511 | /* We haven't checked in, so go dump stack. */ |
| 512 | print_cpu_stall(rsp); |
| 513 | |
| 514 | } else if (rsp->gpnum != rsp->completed && |
| 515 | delta >= RCU_STALL_RAT_DELAY) { |
| 516 | |
| 517 | /* They had two time units to dump stack, so complain. */ |
| 518 | print_other_cpu_stall(rsp); |
| 519 | } |
| 520 | } |
| 521 | |
| 522 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 523 | |
| 524 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
| 525 | { |
| 526 | } |
| 527 | |
| 528 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| 529 | { |
| 530 | } |
| 531 | |
| 532 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 533 | |
| 534 | /* |
| 535 | * Update CPU-local rcu_data state to record the newly noticed grace period. |
| 536 | * This is used both when we started the grace period and when we notice |
| 537 | * that someone else started the grace period. |
| 538 | */ |
| 539 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
| 540 | { |
| 541 | rdp->qs_pending = 1; |
| 542 | rdp->passed_quiesc = 0; |
| 543 | rdp->gpnum = rsp->gpnum; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 544 | } |
| 545 | |
| 546 | /* |
| 547 | * Did someone else start a new RCU grace period start since we last |
| 548 | * checked? Update local state appropriately if so. Must be called |
| 549 | * on the CPU corresponding to rdp. |
| 550 | */ |
| 551 | static int |
| 552 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
| 553 | { |
| 554 | unsigned long flags; |
| 555 | int ret = 0; |
| 556 | |
| 557 | local_irq_save(flags); |
| 558 | if (rdp->gpnum != rsp->gpnum) { |
| 559 | note_new_gpnum(rsp, rdp); |
| 560 | ret = 1; |
| 561 | } |
| 562 | local_irq_restore(flags); |
| 563 | return ret; |
| 564 | } |
| 565 | |
| 566 | /* |
| 567 | * Start a new RCU grace period if warranted, re-initializing the hierarchy |
| 568 | * in preparation for detecting the next grace period. The caller must hold |
| 569 | * the root node's ->lock, which is released before return. Hard irqs must |
| 570 | * be disabled. |
| 571 | */ |
| 572 | static void |
| 573 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) |
| 574 | __releases(rcu_get_root(rsp)->lock) |
| 575 | { |
| 576 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
| 577 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 578 | struct rcu_node *rnp_cur; |
| 579 | struct rcu_node *rnp_end; |
| 580 | |
| 581 | if (!cpu_needs_another_gp(rsp, rdp)) { |
| 582 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 583 | return; |
| 584 | } |
| 585 | |
| 586 | /* Advance to a new grace period and initialize state. */ |
| 587 | rsp->gpnum++; |
| 588 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
| 589 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 590 | record_gp_stall_check_time(rsp); |
| 591 | dyntick_record_completed(rsp, rsp->completed - 1); |
| 592 | note_new_gpnum(rsp, rdp); |
| 593 | |
| 594 | /* |
| 595 | * Because we are first, we know that all our callbacks will |
| 596 | * be covered by this upcoming grace period, even the ones |
| 597 | * that were registered arbitrarily recently. |
| 598 | */ |
| 599 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 600 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 601 | |
| 602 | /* Special-case the common single-level case. */ |
| 603 | if (NUM_RCU_NODES == 1) { |
| 604 | rnp->qsmask = rnp->qsmaskinit; |
Paul E. McKenney | c12172c | 2009-01-04 20:30:06 -0800 | [diff] [blame] | 605 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 606 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 607 | return; |
| 608 | } |
| 609 | |
| 610 | spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
| 611 | |
| 612 | |
| 613 | /* Exclude any concurrent CPU-hotplug operations. */ |
| 614 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| 615 | |
| 616 | /* |
| 617 | * Set the quiescent-state-needed bits in all the non-leaf RCU |
| 618 | * nodes for all currently online CPUs. This operation relies |
| 619 | * on the layout of the hierarchy within the rsp->node[] array. |
| 620 | * Note that other CPUs will access only the leaves of the |
| 621 | * hierarchy, which still indicate that no grace period is in |
| 622 | * progress. In addition, we have excluded CPU-hotplug operations. |
| 623 | * |
| 624 | * We therefore do not need to hold any locks. Any required |
| 625 | * memory barriers will be supplied by the locks guarding the |
| 626 | * leaf rcu_nodes in the hierarchy. |
| 627 | */ |
| 628 | |
| 629 | rnp_end = rsp->level[NUM_RCU_LVLS - 1]; |
| 630 | for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++) |
| 631 | rnp_cur->qsmask = rnp_cur->qsmaskinit; |
| 632 | |
| 633 | /* |
| 634 | * Now set up the leaf nodes. Here we must be careful. First, |
| 635 | * we need to hold the lock in order to exclude other CPUs, which |
| 636 | * might be contending for the leaf nodes' locks. Second, as |
| 637 | * soon as we initialize a given leaf node, its CPUs might run |
| 638 | * up the rest of the hierarchy. We must therefore acquire locks |
| 639 | * for each node that we touch during this stage. (But we still |
| 640 | * are excluding CPU-hotplug operations.) |
| 641 | * |
| 642 | * Note that the grace period cannot complete until we finish |
| 643 | * the initialization process, as there will be at least one |
| 644 | * qsmask bit set in the root node until that time, namely the |
| 645 | * one corresponding to this CPU. |
| 646 | */ |
| 647 | rnp_end = &rsp->node[NUM_RCU_NODES]; |
| 648 | rnp_cur = rsp->level[NUM_RCU_LVLS - 1]; |
| 649 | for (; rnp_cur < rnp_end; rnp_cur++) { |
| 650 | spin_lock(&rnp_cur->lock); /* irqs already disabled. */ |
| 651 | rnp_cur->qsmask = rnp_cur->qsmaskinit; |
| 652 | spin_unlock(&rnp_cur->lock); /* irqs already disabled. */ |
| 653 | } |
| 654 | |
| 655 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
| 656 | spin_unlock_irqrestore(&rsp->onofflock, flags); |
| 657 | } |
| 658 | |
| 659 | /* |
| 660 | * Advance this CPU's callbacks, but only if the current grace period |
| 661 | * has ended. This may be called only from the CPU to whom the rdp |
| 662 | * belongs. |
| 663 | */ |
| 664 | static void |
| 665 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
| 666 | { |
| 667 | long completed_snap; |
| 668 | unsigned long flags; |
| 669 | |
| 670 | local_irq_save(flags); |
| 671 | completed_snap = ACCESS_ONCE(rsp->completed); /* outside of lock. */ |
| 672 | |
| 673 | /* Did another grace period end? */ |
| 674 | if (rdp->completed != completed_snap) { |
| 675 | |
| 676 | /* Advance callbacks. No harm if list empty. */ |
| 677 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; |
| 678 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; |
| 679 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 680 | |
| 681 | /* Remember that we saw this grace-period completion. */ |
| 682 | rdp->completed = completed_snap; |
| 683 | } |
| 684 | local_irq_restore(flags); |
| 685 | } |
| 686 | |
| 687 | /* |
| 688 | * Similar to cpu_quiet(), for which it is a helper function. Allows |
| 689 | * a group of CPUs to be quieted at one go, though all the CPUs in the |
| 690 | * group must be represented by the same leaf rcu_node structure. |
| 691 | * That structure's lock must be held upon entry, and it is released |
| 692 | * before return. |
| 693 | */ |
| 694 | static void |
| 695 | cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, |
| 696 | unsigned long flags) |
| 697 | __releases(rnp->lock) |
| 698 | { |
| 699 | /* Walk up the rcu_node hierarchy. */ |
| 700 | for (;;) { |
| 701 | if (!(rnp->qsmask & mask)) { |
| 702 | |
| 703 | /* Our bit has already been cleared, so done. */ |
| 704 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 705 | return; |
| 706 | } |
| 707 | rnp->qsmask &= ~mask; |
| 708 | if (rnp->qsmask != 0) { |
| 709 | |
| 710 | /* Other bits still set at this level, so done. */ |
| 711 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 712 | return; |
| 713 | } |
| 714 | mask = rnp->grpmask; |
| 715 | if (rnp->parent == NULL) { |
| 716 | |
| 717 | /* No more levels. Exit loop holding root lock. */ |
| 718 | |
| 719 | break; |
| 720 | } |
| 721 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 722 | rnp = rnp->parent; |
| 723 | spin_lock_irqsave(&rnp->lock, flags); |
| 724 | } |
| 725 | |
| 726 | /* |
| 727 | * Get here if we are the last CPU to pass through a quiescent |
| 728 | * state for this grace period. Clean up and let rcu_start_gp() |
| 729 | * start up the next grace period if one is needed. Note that |
| 730 | * we still hold rnp->lock, as required by rcu_start_gp(), which |
| 731 | * will release it. |
| 732 | */ |
| 733 | rsp->completed = rsp->gpnum; |
| 734 | rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]); |
| 735 | rcu_start_gp(rsp, flags); /* releases rnp->lock. */ |
| 736 | } |
| 737 | |
| 738 | /* |
| 739 | * Record a quiescent state for the specified CPU, which must either be |
| 740 | * the current CPU or an offline CPU. The lastcomp argument is used to |
| 741 | * make sure we are still in the grace period of interest. We don't want |
| 742 | * to end the current grace period based on quiescent states detected in |
| 743 | * an earlier grace period! |
| 744 | */ |
| 745 | static void |
| 746 | cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
| 747 | { |
| 748 | unsigned long flags; |
| 749 | unsigned long mask; |
| 750 | struct rcu_node *rnp; |
| 751 | |
| 752 | rnp = rdp->mynode; |
| 753 | spin_lock_irqsave(&rnp->lock, flags); |
| 754 | if (lastcomp != ACCESS_ONCE(rsp->completed)) { |
| 755 | |
| 756 | /* |
| 757 | * Someone beat us to it for this grace period, so leave. |
| 758 | * The race with GP start is resolved by the fact that we |
| 759 | * hold the leaf rcu_node lock, so that the per-CPU bits |
| 760 | * cannot yet be initialized -- so we would simply find our |
| 761 | * CPU's bit already cleared in cpu_quiet_msk() if this race |
| 762 | * occurred. |
| 763 | */ |
| 764 | rdp->passed_quiesc = 0; /* try again later! */ |
| 765 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 766 | return; |
| 767 | } |
| 768 | mask = rdp->grpmask; |
| 769 | if ((rnp->qsmask & mask) == 0) { |
| 770 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 771 | } else { |
| 772 | rdp->qs_pending = 0; |
| 773 | |
| 774 | /* |
| 775 | * This GP can't end until cpu checks in, so all of our |
| 776 | * callbacks can be processed during the next GP. |
| 777 | */ |
| 778 | rdp = rsp->rda[smp_processor_id()]; |
| 779 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 780 | |
| 781 | cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */ |
| 782 | } |
| 783 | } |
| 784 | |
| 785 | /* |
| 786 | * Check to see if there is a new grace period of which this CPU |
| 787 | * is not yet aware, and if so, set up local rcu_data state for it. |
| 788 | * Otherwise, see if this CPU has just passed through its first |
| 789 | * quiescent state for this grace period, and record that fact if so. |
| 790 | */ |
| 791 | static void |
| 792 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
| 793 | { |
| 794 | /* If there is now a new grace period, record and return. */ |
| 795 | if (check_for_new_grace_period(rsp, rdp)) |
| 796 | return; |
| 797 | |
| 798 | /* |
| 799 | * Does this CPU still need to do its part for current grace period? |
| 800 | * If no, return and let the other CPUs do their part as well. |
| 801 | */ |
| 802 | if (!rdp->qs_pending) |
| 803 | return; |
| 804 | |
| 805 | /* |
| 806 | * Was there a quiescent state since the beginning of the grace |
| 807 | * period? If no, then exit and wait for the next call. |
| 808 | */ |
| 809 | if (!rdp->passed_quiesc) |
| 810 | return; |
| 811 | |
| 812 | /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */ |
| 813 | cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); |
| 814 | } |
| 815 | |
| 816 | #ifdef CONFIG_HOTPLUG_CPU |
| 817 | |
| 818 | /* |
| 819 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy |
| 820 | * and move all callbacks from the outgoing CPU to the current one. |
| 821 | */ |
| 822 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) |
| 823 | { |
| 824 | int i; |
| 825 | unsigned long flags; |
| 826 | long lastcomp; |
| 827 | unsigned long mask; |
| 828 | struct rcu_data *rdp = rsp->rda[cpu]; |
| 829 | struct rcu_data *rdp_me; |
| 830 | struct rcu_node *rnp; |
| 831 | |
| 832 | /* Exclude any attempts to start a new grace period. */ |
| 833 | spin_lock_irqsave(&rsp->onofflock, flags); |
| 834 | |
| 835 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
| 836 | rnp = rdp->mynode; |
| 837 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
| 838 | do { |
| 839 | spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 840 | rnp->qsmaskinit &= ~mask; |
| 841 | if (rnp->qsmaskinit != 0) { |
| 842 | spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| 843 | break; |
| 844 | } |
| 845 | mask = rnp->grpmask; |
| 846 | spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| 847 | rnp = rnp->parent; |
| 848 | } while (rnp != NULL); |
| 849 | lastcomp = rsp->completed; |
| 850 | |
| 851 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
| 852 | |
| 853 | /* Being offline is a quiescent state, so go record it. */ |
| 854 | cpu_quiet(cpu, rsp, rdp, lastcomp); |
| 855 | |
| 856 | /* |
| 857 | * Move callbacks from the outgoing CPU to the running CPU. |
| 858 | * Note that the outgoing CPU is now quiscent, so it is now |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 859 | * (uncharacteristically) safe to access its rcu_data structure. |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 860 | * Note also that we must carefully retain the order of the |
| 861 | * outgoing CPU's callbacks in order for rcu_barrier() to work |
| 862 | * correctly. Finally, note that we start all the callbacks |
| 863 | * afresh, even those that have passed through a grace period |
| 864 | * and are therefore ready to invoke. The theory is that hotplug |
| 865 | * events are rare, and that if they are frequent enough to |
| 866 | * indefinitely delay callbacks, you have far worse things to |
| 867 | * be worrying about. |
| 868 | */ |
| 869 | rdp_me = rsp->rda[smp_processor_id()]; |
| 870 | if (rdp->nxtlist != NULL) { |
| 871 | *rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist; |
| 872 | rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 873 | rdp->nxtlist = NULL; |
| 874 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
| 875 | rdp->nxttail[i] = &rdp->nxtlist; |
| 876 | rdp_me->qlen += rdp->qlen; |
| 877 | rdp->qlen = 0; |
| 878 | } |
| 879 | local_irq_restore(flags); |
| 880 | } |
| 881 | |
| 882 | /* |
| 883 | * Remove the specified CPU from the RCU hierarchy and move any pending |
| 884 | * callbacks that it might have to the current CPU. This code assumes |
| 885 | * that at least one CPU in the system will remain running at all times. |
| 886 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. |
| 887 | */ |
| 888 | static void rcu_offline_cpu(int cpu) |
| 889 | { |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 890 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 891 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
| 892 | } |
| 893 | |
| 894 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 895 | |
| 896 | static void rcu_offline_cpu(int cpu) |
| 897 | { |
| 898 | } |
| 899 | |
| 900 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
| 901 | |
| 902 | /* |
| 903 | * Invoke any RCU callbacks that have made it to the end of their grace |
| 904 | * period. Thottle as specified by rdp->blimit. |
| 905 | */ |
| 906 | static void rcu_do_batch(struct rcu_data *rdp) |
| 907 | { |
| 908 | unsigned long flags; |
| 909 | struct rcu_head *next, *list, **tail; |
| 910 | int count; |
| 911 | |
| 912 | /* If no callbacks are ready, just return.*/ |
| 913 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) |
| 914 | return; |
| 915 | |
| 916 | /* |
| 917 | * Extract the list of ready callbacks, disabling to prevent |
| 918 | * races with call_rcu() from interrupt handlers. |
| 919 | */ |
| 920 | local_irq_save(flags); |
| 921 | list = rdp->nxtlist; |
| 922 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
| 923 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
| 924 | tail = rdp->nxttail[RCU_DONE_TAIL]; |
| 925 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) |
| 926 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) |
| 927 | rdp->nxttail[count] = &rdp->nxtlist; |
| 928 | local_irq_restore(flags); |
| 929 | |
| 930 | /* Invoke callbacks. */ |
| 931 | count = 0; |
| 932 | while (list) { |
| 933 | next = list->next; |
| 934 | prefetch(next); |
| 935 | list->func(list); |
| 936 | list = next; |
| 937 | if (++count >= rdp->blimit) |
| 938 | break; |
| 939 | } |
| 940 | |
| 941 | local_irq_save(flags); |
| 942 | |
| 943 | /* Update count, and requeue any remaining callbacks. */ |
| 944 | rdp->qlen -= count; |
| 945 | if (list != NULL) { |
| 946 | *tail = rdp->nxtlist; |
| 947 | rdp->nxtlist = list; |
| 948 | for (count = 0; count < RCU_NEXT_SIZE; count++) |
| 949 | if (&rdp->nxtlist == rdp->nxttail[count]) |
| 950 | rdp->nxttail[count] = tail; |
| 951 | else |
| 952 | break; |
| 953 | } |
| 954 | |
| 955 | /* Reinstate batch limit if we have worked down the excess. */ |
| 956 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
| 957 | rdp->blimit = blimit; |
| 958 | |
| 959 | local_irq_restore(flags); |
| 960 | |
| 961 | /* Re-raise the RCU softirq if there are callbacks remaining. */ |
| 962 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| 963 | raise_softirq(RCU_SOFTIRQ); |
| 964 | } |
| 965 | |
| 966 | /* |
| 967 | * Check to see if this CPU is in a non-context-switch quiescent state |
| 968 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
| 969 | * Also schedule the RCU softirq handler. |
| 970 | * |
| 971 | * This function must be called with hardirqs disabled. It is normally |
| 972 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
| 973 | * false, there is no point in invoking rcu_check_callbacks(). |
| 974 | */ |
| 975 | void rcu_check_callbacks(int cpu, int user) |
| 976 | { |
| 977 | if (user || |
Paul E. McKenney | a682604 | 2009-02-25 18:03:42 -0800 | [diff] [blame] | 978 | (idle_cpu(cpu) && rcu_scheduler_active && |
| 979 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 980 | |
| 981 | /* |
| 982 | * Get here if this CPU took its interrupt from user |
| 983 | * mode or from the idle loop, and if this is not a |
| 984 | * nested interrupt. In this case, the CPU is in |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 985 | * a quiescent state, so note it. |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 986 | * |
| 987 | * No memory barrier is required here because both |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 988 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
| 989 | * variables that other CPUs neither access nor modify, |
| 990 | * at least not while the corresponding CPU is online. |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 991 | */ |
| 992 | |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 993 | rcu_sched_qs(cpu); |
| 994 | rcu_bh_qs(cpu); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 995 | |
| 996 | } else if (!in_softirq()) { |
| 997 | |
| 998 | /* |
| 999 | * Get here if this CPU did not take its interrupt from |
| 1000 | * softirq, in other words, if it is not interrupting |
| 1001 | * a rcu_bh read-side critical section. This is an _bh |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1002 | * critical section, so note it. |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1003 | */ |
| 1004 | |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1005 | rcu_bh_qs(cpu); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1006 | } |
| 1007 | raise_softirq(RCU_SOFTIRQ); |
| 1008 | } |
| 1009 | |
| 1010 | #ifdef CONFIG_SMP |
| 1011 | |
| 1012 | /* |
| 1013 | * Scan the leaf rcu_node structures, processing dyntick state for any that |
| 1014 | * have not yet encountered a quiescent state, using the function specified. |
| 1015 | * Returns 1 if the current grace period ends while scanning (possibly |
| 1016 | * because we made it end). |
| 1017 | */ |
| 1018 | static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp, |
| 1019 | int (*f)(struct rcu_data *)) |
| 1020 | { |
| 1021 | unsigned long bit; |
| 1022 | int cpu; |
| 1023 | unsigned long flags; |
| 1024 | unsigned long mask; |
| 1025 | struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1]; |
| 1026 | struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES]; |
| 1027 | |
| 1028 | for (; rnp_cur < rnp_end; rnp_cur++) { |
| 1029 | mask = 0; |
| 1030 | spin_lock_irqsave(&rnp_cur->lock, flags); |
| 1031 | if (rsp->completed != lastcomp) { |
| 1032 | spin_unlock_irqrestore(&rnp_cur->lock, flags); |
| 1033 | return 1; |
| 1034 | } |
| 1035 | if (rnp_cur->qsmask == 0) { |
| 1036 | spin_unlock_irqrestore(&rnp_cur->lock, flags); |
| 1037 | continue; |
| 1038 | } |
| 1039 | cpu = rnp_cur->grplo; |
| 1040 | bit = 1; |
| 1041 | for (; cpu <= rnp_cur->grphi; cpu++, bit <<= 1) { |
| 1042 | if ((rnp_cur->qsmask & bit) != 0 && f(rsp->rda[cpu])) |
| 1043 | mask |= bit; |
| 1044 | } |
| 1045 | if (mask != 0 && rsp->completed == lastcomp) { |
| 1046 | |
| 1047 | /* cpu_quiet_msk() releases rnp_cur->lock. */ |
| 1048 | cpu_quiet_msk(mask, rsp, rnp_cur, flags); |
| 1049 | continue; |
| 1050 | } |
| 1051 | spin_unlock_irqrestore(&rnp_cur->lock, flags); |
| 1052 | } |
| 1053 | return 0; |
| 1054 | } |
| 1055 | |
| 1056 | /* |
| 1057 | * Force quiescent states on reluctant CPUs, and also detect which |
| 1058 | * CPUs are in dyntick-idle mode. |
| 1059 | */ |
| 1060 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| 1061 | { |
| 1062 | unsigned long flags; |
| 1063 | long lastcomp; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1064 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 1065 | u8 signaled; |
| 1066 | |
| 1067 | if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) |
| 1068 | return; /* No grace period in progress, nothing to force. */ |
| 1069 | if (!spin_trylock_irqsave(&rsp->fqslock, flags)) { |
| 1070 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
| 1071 | return; /* Someone else is already on the job. */ |
| 1072 | } |
| 1073 | if (relaxed && |
Paul E. McKenney | ef631b0 | 2009-04-13 21:31:16 -0700 | [diff] [blame] | 1074 | (long)(rsp->jiffies_force_qs - jiffies) >= 0) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1075 | goto unlock_ret; /* no emergency and done recently. */ |
| 1076 | rsp->n_force_qs++; |
| 1077 | spin_lock(&rnp->lock); |
| 1078 | lastcomp = rsp->completed; |
| 1079 | signaled = rsp->signaled; |
| 1080 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1081 | if (lastcomp == rsp->gpnum) { |
| 1082 | rsp->n_force_qs_ngp++; |
| 1083 | spin_unlock(&rnp->lock); |
| 1084 | goto unlock_ret; /* no GP in progress, time updated. */ |
| 1085 | } |
| 1086 | spin_unlock(&rnp->lock); |
| 1087 | switch (signaled) { |
| 1088 | case RCU_GP_INIT: |
| 1089 | |
| 1090 | break; /* grace period still initializing, ignore. */ |
| 1091 | |
| 1092 | case RCU_SAVE_DYNTICK: |
| 1093 | |
| 1094 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
| 1095 | break; /* So gcc recognizes the dead code. */ |
| 1096 | |
| 1097 | /* Record dyntick-idle state. */ |
| 1098 | if (rcu_process_dyntick(rsp, lastcomp, |
| 1099 | dyntick_save_progress_counter)) |
| 1100 | goto unlock_ret; |
| 1101 | |
| 1102 | /* Update state, record completion counter. */ |
| 1103 | spin_lock(&rnp->lock); |
| 1104 | if (lastcomp == rsp->completed) { |
| 1105 | rsp->signaled = RCU_FORCE_QS; |
| 1106 | dyntick_record_completed(rsp, lastcomp); |
| 1107 | } |
| 1108 | spin_unlock(&rnp->lock); |
| 1109 | break; |
| 1110 | |
| 1111 | case RCU_FORCE_QS: |
| 1112 | |
| 1113 | /* Check dyntick-idle state, send IPI to laggarts. */ |
| 1114 | if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp), |
| 1115 | rcu_implicit_dynticks_qs)) |
| 1116 | goto unlock_ret; |
| 1117 | |
| 1118 | /* Leave state in case more forcing is required. */ |
| 1119 | |
| 1120 | break; |
| 1121 | } |
| 1122 | unlock_ret: |
| 1123 | spin_unlock_irqrestore(&rsp->fqslock, flags); |
| 1124 | } |
| 1125 | |
| 1126 | #else /* #ifdef CONFIG_SMP */ |
| 1127 | |
| 1128 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| 1129 | { |
| 1130 | set_need_resched(); |
| 1131 | } |
| 1132 | |
| 1133 | #endif /* #else #ifdef CONFIG_SMP */ |
| 1134 | |
| 1135 | /* |
| 1136 | * This does the RCU processing work from softirq context for the |
| 1137 | * specified rcu_state and rcu_data structures. This may be called |
| 1138 | * only from the CPU to whom the rdp belongs. |
| 1139 | */ |
| 1140 | static void |
| 1141 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
| 1142 | { |
| 1143 | unsigned long flags; |
| 1144 | |
Paul E. McKenney | 2e59755 | 2009-08-15 09:53:48 -0700 | [diff] [blame] | 1145 | WARN_ON_ONCE(rdp->beenonline == 0); |
| 1146 | |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1147 | /* |
| 1148 | * If an RCU GP has gone long enough, go check for dyntick |
| 1149 | * idle CPUs and, if needed, send resched IPIs. |
| 1150 | */ |
Paul E. McKenney | ef631b0 | 2009-04-13 21:31:16 -0700 | [diff] [blame] | 1151 | if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1152 | force_quiescent_state(rsp, 1); |
| 1153 | |
| 1154 | /* |
| 1155 | * Advance callbacks in response to end of earlier grace |
| 1156 | * period that some other CPU ended. |
| 1157 | */ |
| 1158 | rcu_process_gp_end(rsp, rdp); |
| 1159 | |
| 1160 | /* Update RCU state based on any recent quiescent states. */ |
| 1161 | rcu_check_quiescent_state(rsp, rdp); |
| 1162 | |
| 1163 | /* Does this CPU require a not-yet-started grace period? */ |
| 1164 | if (cpu_needs_another_gp(rsp, rdp)) { |
| 1165 | spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
| 1166 | rcu_start_gp(rsp, flags); /* releases above lock */ |
| 1167 | } |
| 1168 | |
| 1169 | /* If there are callbacks ready, invoke them. */ |
| 1170 | rcu_do_batch(rdp); |
| 1171 | } |
| 1172 | |
| 1173 | /* |
| 1174 | * Do softirq processing for the current CPU. |
| 1175 | */ |
| 1176 | static void rcu_process_callbacks(struct softirq_action *unused) |
| 1177 | { |
| 1178 | /* |
| 1179 | * Memory references from any prior RCU read-side critical sections |
| 1180 | * executed by the interrupted code must be seen before any RCU |
| 1181 | * grace-period manipulations below. |
| 1182 | */ |
| 1183 | smp_mb(); /* See above block comment. */ |
| 1184 | |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1185 | __rcu_process_callbacks(&rcu_sched_state, |
| 1186 | &__get_cpu_var(rcu_sched_data)); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1187 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
| 1188 | |
| 1189 | /* |
| 1190 | * Memory references from any later RCU read-side critical sections |
| 1191 | * executed by the interrupted code must be seen after any RCU |
| 1192 | * grace-period manipulations above. |
| 1193 | */ |
| 1194 | smp_mb(); /* See above block comment. */ |
| 1195 | } |
| 1196 | |
| 1197 | static void |
| 1198 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
| 1199 | struct rcu_state *rsp) |
| 1200 | { |
| 1201 | unsigned long flags; |
| 1202 | struct rcu_data *rdp; |
| 1203 | |
| 1204 | head->func = func; |
| 1205 | head->next = NULL; |
| 1206 | |
| 1207 | smp_mb(); /* Ensure RCU update seen before callback registry. */ |
| 1208 | |
| 1209 | /* |
| 1210 | * Opportunistically note grace-period endings and beginnings. |
| 1211 | * Note that we might see a beginning right after we see an |
| 1212 | * end, but never vice versa, since this CPU has to pass through |
| 1213 | * a quiescent state betweentimes. |
| 1214 | */ |
| 1215 | local_irq_save(flags); |
| 1216 | rdp = rsp->rda[smp_processor_id()]; |
| 1217 | rcu_process_gp_end(rsp, rdp); |
| 1218 | check_for_new_grace_period(rsp, rdp); |
| 1219 | |
| 1220 | /* Add the callback to our list. */ |
| 1221 | *rdp->nxttail[RCU_NEXT_TAIL] = head; |
| 1222 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
| 1223 | |
| 1224 | /* Start a new grace period if one not already started. */ |
| 1225 | if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) { |
| 1226 | unsigned long nestflag; |
| 1227 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
| 1228 | |
| 1229 | spin_lock_irqsave(&rnp_root->lock, nestflag); |
| 1230 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ |
| 1231 | } |
| 1232 | |
| 1233 | /* Force the grace period if too many callbacks or too long waiting. */ |
| 1234 | if (unlikely(++rdp->qlen > qhimark)) { |
| 1235 | rdp->blimit = LONG_MAX; |
| 1236 | force_quiescent_state(rsp, 0); |
Paul E. McKenney | ef631b0 | 2009-04-13 21:31:16 -0700 | [diff] [blame] | 1237 | } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1238 | force_quiescent_state(rsp, 1); |
| 1239 | local_irq_restore(flags); |
| 1240 | } |
| 1241 | |
| 1242 | /* |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1243 | * Queue an RCU-sched callback for invocation after a grace period. |
| 1244 | */ |
| 1245 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| 1246 | { |
| 1247 | __call_rcu(head, func, &rcu_sched_state); |
| 1248 | } |
| 1249 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
| 1250 | |
| 1251 | /* |
| 1252 | * @@@ Queue an RCU callback for invocation after a grace period. |
| 1253 | * @@@ Placeholder pending rcutree_plugin.h. |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1254 | */ |
| 1255 | void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| 1256 | { |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1257 | call_rcu_sched(head, func); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1258 | } |
| 1259 | EXPORT_SYMBOL_GPL(call_rcu); |
| 1260 | |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1261 | |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1262 | /* |
| 1263 | * Queue an RCU for invocation after a quicker grace period. |
| 1264 | */ |
| 1265 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| 1266 | { |
| 1267 | __call_rcu(head, func, &rcu_bh_state); |
| 1268 | } |
| 1269 | EXPORT_SYMBOL_GPL(call_rcu_bh); |
| 1270 | |
| 1271 | /* |
| 1272 | * Check to see if there is any immediate RCU-related work to be done |
| 1273 | * by the current CPU, for the specified type of RCU, returning 1 if so. |
| 1274 | * The checks are in order of increasing expense: checks that can be |
| 1275 | * carried out against CPU-local state are performed first. However, |
| 1276 | * we must check for CPU stalls first, else we might not get a chance. |
| 1277 | */ |
| 1278 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
| 1279 | { |
| 1280 | rdp->n_rcu_pending++; |
| 1281 | |
| 1282 | /* Check for CPU stalls, if enabled. */ |
| 1283 | check_cpu_stall(rsp, rdp); |
| 1284 | |
| 1285 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1286 | if (rdp->qs_pending) { |
| 1287 | rdp->n_rp_qs_pending++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1288 | return 1; |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1289 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1290 | |
| 1291 | /* Does this CPU have callbacks ready to invoke? */ |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1292 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
| 1293 | rdp->n_rp_cb_ready++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1294 | return 1; |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1295 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1296 | |
| 1297 | /* Has RCU gone idle with this CPU needing another grace period? */ |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1298 | if (cpu_needs_another_gp(rsp, rdp)) { |
| 1299 | rdp->n_rp_cpu_needs_gp++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1300 | return 1; |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1301 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1302 | |
| 1303 | /* Has another RCU grace period completed? */ |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1304 | if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */ |
| 1305 | rdp->n_rp_gp_completed++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1306 | return 1; |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1307 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1308 | |
| 1309 | /* Has a new RCU grace period started? */ |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1310 | if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */ |
| 1311 | rdp->n_rp_gp_started++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1312 | return 1; |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1313 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1314 | |
| 1315 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ |
| 1316 | if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) && |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1317 | ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) { |
| 1318 | rdp->n_rp_need_fqs++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1319 | return 1; |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1320 | } |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1321 | |
| 1322 | /* nothing to do */ |
Paul E. McKenney | 7ba5c84 | 2009-04-13 21:31:17 -0700 | [diff] [blame] | 1323 | rdp->n_rp_need_nothing++; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1324 | return 0; |
| 1325 | } |
| 1326 | |
| 1327 | /* |
| 1328 | * Check to see if there is any immediate RCU-related work to be done |
| 1329 | * by the current CPU, returning 1 if so. This function is part of the |
| 1330 | * RCU implementation; it is -not- an exported member of the RCU API. |
| 1331 | */ |
| 1332 | int rcu_pending(int cpu) |
| 1333 | { |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1334 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1335 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)); |
| 1336 | } |
| 1337 | |
| 1338 | /* |
| 1339 | * Check to see if any future RCU-related work will need to be done |
| 1340 | * by the current CPU, even if none need be done immediately, returning |
| 1341 | * 1 if so. This function is part of the RCU implementation; it is -not- |
| 1342 | * an exported member of the RCU API. |
| 1343 | */ |
| 1344 | int rcu_needs_cpu(int cpu) |
| 1345 | { |
| 1346 | /* RCU callbacks either ready or pending? */ |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1347 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1348 | per_cpu(rcu_bh_data, cpu).nxtlist; |
| 1349 | } |
| 1350 | |
| 1351 | /* |
Paul E. McKenney | 2756962 | 2009-08-15 09:53:46 -0700 | [diff] [blame] | 1352 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
| 1353 | */ |
| 1354 | static void __init |
| 1355 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
| 1356 | { |
| 1357 | unsigned long flags; |
| 1358 | int i; |
| 1359 | struct rcu_data *rdp = rsp->rda[cpu]; |
| 1360 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 1361 | |
| 1362 | /* Set up local state, ensuring consistent view of global state. */ |
| 1363 | spin_lock_irqsave(&rnp->lock, flags); |
| 1364 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
| 1365 | rdp->nxtlist = NULL; |
| 1366 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
| 1367 | rdp->nxttail[i] = &rdp->nxtlist; |
| 1368 | rdp->qlen = 0; |
| 1369 | #ifdef CONFIG_NO_HZ |
| 1370 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
| 1371 | #endif /* #ifdef CONFIG_NO_HZ */ |
| 1372 | rdp->cpu = cpu; |
| 1373 | spin_unlock_irqrestore(&rnp->lock, flags); |
| 1374 | } |
| 1375 | |
| 1376 | /* |
| 1377 | * Initialize a CPU's per-CPU RCU data. Note that only one online or |
| 1378 | * offline event can be happening at a given time. Note also that we |
| 1379 | * can accept some slop in the rsp->completed access due to the fact |
| 1380 | * that this CPU cannot possibly have any RCU callbacks in flight yet. |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1381 | */ |
Lai Jiangshan | e4fa4c9 | 2009-01-14 14:58:15 +0800 | [diff] [blame] | 1382 | static void __cpuinit |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1383 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp) |
| 1384 | { |
| 1385 | unsigned long flags; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1386 | long lastcomp; |
| 1387 | unsigned long mask; |
| 1388 | struct rcu_data *rdp = rsp->rda[cpu]; |
| 1389 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 1390 | |
| 1391 | /* Set up local state, ensuring consistent view of global state. */ |
| 1392 | spin_lock_irqsave(&rnp->lock, flags); |
| 1393 | lastcomp = rsp->completed; |
| 1394 | rdp->completed = lastcomp; |
| 1395 | rdp->gpnum = lastcomp; |
| 1396 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
| 1397 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ |
| 1398 | rdp->beenonline = 1; /* We have now been online. */ |
| 1399 | rdp->passed_quiesc_completed = lastcomp - 1; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1400 | rdp->blimit = blimit; |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1401 | spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 1402 | |
| 1403 | /* |
| 1404 | * A new grace period might start here. If so, we won't be part |
| 1405 | * of it, but that is OK, as we are currently in a quiescent state. |
| 1406 | */ |
| 1407 | |
| 1408 | /* Exclude any attempts to start a new GP on large systems. */ |
| 1409 | spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| 1410 | |
| 1411 | /* Add CPU to rcu_node bitmasks. */ |
| 1412 | rnp = rdp->mynode; |
| 1413 | mask = rdp->grpmask; |
| 1414 | do { |
| 1415 | /* Exclude any attempts to start a new GP on small systems. */ |
| 1416 | spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 1417 | rnp->qsmaskinit |= mask; |
| 1418 | mask = rnp->grpmask; |
| 1419 | spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| 1420 | rnp = rnp->parent; |
| 1421 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
| 1422 | |
| 1423 | spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
| 1424 | |
| 1425 | /* |
| 1426 | * A new grace period might start here. If so, we will be part of |
| 1427 | * it, and its gpnum will be greater than ours, so we will |
| 1428 | * participate. It is also possible for the gpnum to have been |
| 1429 | * incremented before this function was called, and the bitmasks |
| 1430 | * to not be filled out until now, in which case we will also |
| 1431 | * participate due to our gpnum being behind. |
| 1432 | */ |
| 1433 | |
| 1434 | /* Since it is coming online, the CPU is in a quiescent state. */ |
| 1435 | cpu_quiet(cpu, rsp, rdp, lastcomp); |
| 1436 | local_irq_restore(flags); |
| 1437 | } |
| 1438 | |
| 1439 | static void __cpuinit rcu_online_cpu(int cpu) |
| 1440 | { |
Paul E. McKenney | d6714c2 | 2009-08-22 13:56:46 -0700 | [diff] [blame] | 1441 | rcu_init_percpu_data(cpu, &rcu_sched_state); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1442 | rcu_init_percpu_data(cpu, &rcu_bh_state); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1443 | } |
| 1444 | |
| 1445 | /* |
| 1446 | * Handle CPU online/offline notifcation events. |
| 1447 | */ |
Paul E. McKenney | 2e59755 | 2009-08-15 09:53:48 -0700 | [diff] [blame] | 1448 | int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
| 1449 | unsigned long action, void *hcpu) |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1450 | { |
| 1451 | long cpu = (long)hcpu; |
| 1452 | |
| 1453 | switch (action) { |
| 1454 | case CPU_UP_PREPARE: |
| 1455 | case CPU_UP_PREPARE_FROZEN: |
| 1456 | rcu_online_cpu(cpu); |
| 1457 | break; |
| 1458 | case CPU_DEAD: |
| 1459 | case CPU_DEAD_FROZEN: |
| 1460 | case CPU_UP_CANCELED: |
| 1461 | case CPU_UP_CANCELED_FROZEN: |
| 1462 | rcu_offline_cpu(cpu); |
| 1463 | break; |
| 1464 | default: |
| 1465 | break; |
| 1466 | } |
| 1467 | return NOTIFY_OK; |
| 1468 | } |
| 1469 | |
| 1470 | /* |
| 1471 | * Compute the per-level fanout, either using the exact fanout specified |
| 1472 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
| 1473 | */ |
| 1474 | #ifdef CONFIG_RCU_FANOUT_EXACT |
| 1475 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| 1476 | { |
| 1477 | int i; |
| 1478 | |
| 1479 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) |
| 1480 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
| 1481 | } |
| 1482 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| 1483 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| 1484 | { |
| 1485 | int ccur; |
| 1486 | int cprv; |
| 1487 | int i; |
| 1488 | |
| 1489 | cprv = NR_CPUS; |
| 1490 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| 1491 | ccur = rsp->levelcnt[i]; |
| 1492 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
| 1493 | cprv = ccur; |
| 1494 | } |
| 1495 | } |
| 1496 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| 1497 | |
| 1498 | /* |
| 1499 | * Helper function for rcu_init() that initializes one rcu_state structure. |
| 1500 | */ |
| 1501 | static void __init rcu_init_one(struct rcu_state *rsp) |
| 1502 | { |
| 1503 | int cpustride = 1; |
| 1504 | int i; |
| 1505 | int j; |
| 1506 | struct rcu_node *rnp; |
| 1507 | |
| 1508 | /* Initialize the level-tracking arrays. */ |
| 1509 | |
| 1510 | for (i = 1; i < NUM_RCU_LVLS; i++) |
| 1511 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
| 1512 | rcu_init_levelspread(rsp); |
| 1513 | |
| 1514 | /* Initialize the elements themselves, starting from the leaves. */ |
| 1515 | |
| 1516 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| 1517 | cpustride *= rsp->levelspread[i]; |
| 1518 | rnp = rsp->level[i]; |
| 1519 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
| 1520 | spin_lock_init(&rnp->lock); |
| 1521 | rnp->qsmask = 0; |
| 1522 | rnp->qsmaskinit = 0; |
| 1523 | rnp->grplo = j * cpustride; |
| 1524 | rnp->grphi = (j + 1) * cpustride - 1; |
| 1525 | if (rnp->grphi >= NR_CPUS) |
| 1526 | rnp->grphi = NR_CPUS - 1; |
| 1527 | if (i == 0) { |
| 1528 | rnp->grpnum = 0; |
| 1529 | rnp->grpmask = 0; |
| 1530 | rnp->parent = NULL; |
| 1531 | } else { |
| 1532 | rnp->grpnum = j % rsp->levelspread[i - 1]; |
| 1533 | rnp->grpmask = 1UL << rnp->grpnum; |
| 1534 | rnp->parent = rsp->level[i - 1] + |
| 1535 | j / rsp->levelspread[i - 1]; |
| 1536 | } |
| 1537 | rnp->level = i; |
| 1538 | } |
| 1539 | } |
| 1540 | } |
| 1541 | |
| 1542 | /* |
| 1543 | * Helper macro for __rcu_init(). To be used nowhere else! |
| 1544 | * Assigns leaf node pointers into each CPU's rcu_data structure. |
| 1545 | */ |
Paul E. McKenney | 65cf8f8 | 2009-08-22 13:56:49 -0700 | [diff] [blame^] | 1546 | #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1547 | do { \ |
Paul E. McKenney | 65cf8f8 | 2009-08-22 13:56:49 -0700 | [diff] [blame^] | 1548 | rcu_init_one(rsp); \ |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1549 | rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \ |
| 1550 | j = 0; \ |
| 1551 | for_each_possible_cpu(i) { \ |
| 1552 | if (i > rnp[j].grphi) \ |
| 1553 | j++; \ |
| 1554 | per_cpu(rcu_data, i).mynode = &rnp[j]; \ |
| 1555 | (rsp)->rda[i] = &per_cpu(rcu_data, i); \ |
Paul E. McKenney | 65cf8f8 | 2009-08-22 13:56:49 -0700 | [diff] [blame^] | 1556 | rcu_boot_init_percpu_data(i, rsp); \ |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1557 | } \ |
| 1558 | } while (0) |
| 1559 | |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1560 | void __init __rcu_init(void) |
| 1561 | { |
| 1562 | int i; /* All used by RCU_DATA_PTR_INIT(). */ |
| 1563 | int j; |
| 1564 | struct rcu_node *rnp; |
| 1565 | |
Paul E. McKenney | f6faac7 | 2009-06-23 17:24:40 -0700 | [diff] [blame] | 1566 | printk(KERN_INFO "Hierarchical RCU implementation.\n"); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1567 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| 1568 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); |
| 1569 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
Paul E. McKenney | 65cf8f8 | 2009-08-22 13:56:49 -0700 | [diff] [blame^] | 1570 | RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
| 1571 | RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); |
Paul E. McKenney | 2e59755 | 2009-08-15 09:53:48 -0700 | [diff] [blame] | 1572 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
Paul E. McKenney | 64db4cf | 2008-12-18 21:55:32 +0100 | [diff] [blame] | 1573 | } |
| 1574 | |
| 1575 | module_param(blimit, int, 0); |
| 1576 | module_param(qhimark, int, 0); |
| 1577 | module_param(qlowmark, int, 0); |