Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [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 |
Paul E. McKenney | 87de1cf | 2013-12-03 10:02:52 -0800 | [diff] [blame] | 15 | * along with this program; if not, you can access it online at |
| 16 | * http://www.gnu.org/licenses/gpl-2.0.html. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 17 | * |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 18 | * Copyright IBM Corporation, 2001 |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 19 | * |
| 20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| 21 | * Manfred Spraul <manfred@colorfullife.com> |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 22 | * |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| 24 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 25 | * Papers: |
| 26 | * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf |
| 27 | * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) |
| 28 | * |
| 29 | * For detailed explanation of Read-Copy Update mechanism see - |
Paul E. McKenney | a71fca5 | 2009-09-18 10:28:19 -0700 | [diff] [blame] | 30 | * http://lse.sourceforge.net/locking/rcupdate.html |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 31 | * |
| 32 | */ |
| 33 | #include <linux/types.h> |
| 34 | #include <linux/kernel.h> |
| 35 | #include <linux/init.h> |
| 36 | #include <linux/spinlock.h> |
| 37 | #include <linux/smp.h> |
| 38 | #include <linux/interrupt.h> |
| 39 | #include <linux/sched.h> |
Arun Sharma | 60063497 | 2011-07-26 16:09:06 -0700 | [diff] [blame] | 40 | #include <linux/atomic.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 41 | #include <linux/bitops.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 42 | #include <linux/percpu.h> |
| 43 | #include <linux/notifier.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 44 | #include <linux/cpu.h> |
Ingo Molnar | 9331b31 | 2006-03-23 03:00:19 -0800 | [diff] [blame] | 45 | #include <linux/mutex.h> |
Paul Gortmaker | 9984de1 | 2011-05-23 14:51:41 -0400 | [diff] [blame] | 46 | #include <linux/export.h> |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 47 | #include <linux/hardirq.h> |
Paul E. McKenney | e3ebfb9 | 2012-07-02 14:42:01 -0700 | [diff] [blame] | 48 | #include <linux/delay.h> |
Antti P Miettinen | 3705b88 | 2012-10-05 09:59:15 +0300 | [diff] [blame] | 49 | #include <linux/module.h> |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 50 | #include <linux/kthread.h> |
Paul E. McKenney | 4ff475e | 2014-08-10 19:47:12 -0700 | [diff] [blame] | 51 | #include <linux/tick.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 52 | |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 53 | #define CREATE_TRACE_POINTS |
Paul E. McKenney | 29c00b4 | 2011-06-17 15:53:19 -0700 | [diff] [blame] | 54 | |
| 55 | #include "rcu.h" |
| 56 | |
Paul E. McKenney | 4102ada | 2013-10-08 20:23:47 -0700 | [diff] [blame] | 57 | MODULE_ALIAS("rcupdate"); |
| 58 | #ifdef MODULE_PARAM_PREFIX |
| 59 | #undef MODULE_PARAM_PREFIX |
| 60 | #endif |
| 61 | #define MODULE_PARAM_PREFIX "rcupdate." |
| 62 | |
Antti P Miettinen | 3705b88 | 2012-10-05 09:59:15 +0300 | [diff] [blame] | 63 | module_param(rcu_expedited, int, 0); |
| 64 | |
Paul E. McKenney | 0d39482 | 2015-02-18 12:24:30 -0800 | [diff] [blame] | 65 | #ifndef CONFIG_TINY_RCU |
| 66 | |
Paul E. McKenney | ee42571 | 2015-02-19 10:51:32 -0800 | [diff] [blame] | 67 | static atomic_t rcu_expedited_nesting = |
| 68 | ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0); |
Paul E. McKenney | 0d39482 | 2015-02-18 12:24:30 -0800 | [diff] [blame] | 69 | |
| 70 | /* |
| 71 | * Should normal grace-period primitives be expedited? Intended for |
| 72 | * use within RCU. Note that this function takes the rcu_expedited |
| 73 | * sysfs/boot variable into account as well as the rcu_expedite_gp() |
| 74 | * nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited() |
| 75 | * returns false is a -really- bad idea. |
| 76 | */ |
| 77 | bool rcu_gp_is_expedited(void) |
| 78 | { |
| 79 | return rcu_expedited || atomic_read(&rcu_expedited_nesting); |
| 80 | } |
| 81 | EXPORT_SYMBOL_GPL(rcu_gp_is_expedited); |
| 82 | |
| 83 | /** |
| 84 | * rcu_expedite_gp - Expedite future RCU grace periods |
| 85 | * |
| 86 | * After a call to this function, future calls to synchronize_rcu() and |
| 87 | * friends act as the corresponding synchronize_rcu_expedited() function |
| 88 | * had instead been called. |
| 89 | */ |
| 90 | void rcu_expedite_gp(void) |
| 91 | { |
| 92 | atomic_inc(&rcu_expedited_nesting); |
| 93 | } |
| 94 | EXPORT_SYMBOL_GPL(rcu_expedite_gp); |
| 95 | |
| 96 | /** |
| 97 | * rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation |
| 98 | * |
| 99 | * Undo a prior call to rcu_expedite_gp(). If all prior calls to |
| 100 | * rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(), |
| 101 | * and if the rcu_expedited sysfs/boot parameter is not set, then all |
| 102 | * subsequent calls to synchronize_rcu() and friends will return to |
| 103 | * their normal non-expedited behavior. |
| 104 | */ |
| 105 | void rcu_unexpedite_gp(void) |
| 106 | { |
| 107 | atomic_dec(&rcu_expedited_nesting); |
| 108 | } |
| 109 | EXPORT_SYMBOL_GPL(rcu_unexpedite_gp); |
| 110 | |
| 111 | #endif /* #ifndef CONFIG_TINY_RCU */ |
| 112 | |
Paul E. McKenney | ee42571 | 2015-02-19 10:51:32 -0800 | [diff] [blame] | 113 | /* |
| 114 | * Inform RCU of the end of the in-kernel boot sequence. |
| 115 | */ |
| 116 | void rcu_end_inkernel_boot(void) |
| 117 | { |
| 118 | if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT)) |
| 119 | rcu_unexpedite_gp(); |
| 120 | } |
Paul E. McKenney | 0d39482 | 2015-02-18 12:24:30 -0800 | [diff] [blame] | 121 | |
Paul E. McKenney | 9dd8fb1 | 2012-04-13 12:54:22 -0700 | [diff] [blame] | 122 | #ifdef CONFIG_PREEMPT_RCU |
| 123 | |
| 124 | /* |
Paul E. McKenney | 2a3fa84 | 2012-05-21 11:58:36 -0700 | [diff] [blame] | 125 | * Preemptible RCU implementation for rcu_read_lock(). |
| 126 | * Just increment ->rcu_read_lock_nesting, shared state will be updated |
| 127 | * if we block. |
| 128 | */ |
| 129 | void __rcu_read_lock(void) |
| 130 | { |
| 131 | current->rcu_read_lock_nesting++; |
| 132 | barrier(); /* critical section after entry code. */ |
| 133 | } |
| 134 | EXPORT_SYMBOL_GPL(__rcu_read_lock); |
| 135 | |
| 136 | /* |
| 137 | * Preemptible RCU implementation for rcu_read_unlock(). |
| 138 | * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost |
| 139 | * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then |
| 140 | * invoke rcu_read_unlock_special() to clean up after a context switch |
| 141 | * in an RCU read-side critical section and other special cases. |
| 142 | */ |
| 143 | void __rcu_read_unlock(void) |
| 144 | { |
| 145 | struct task_struct *t = current; |
| 146 | |
| 147 | if (t->rcu_read_lock_nesting != 1) { |
| 148 | --t->rcu_read_lock_nesting; |
| 149 | } else { |
| 150 | barrier(); /* critical section before exit code. */ |
| 151 | t->rcu_read_lock_nesting = INT_MIN; |
| 152 | barrier(); /* assign before ->rcu_read_unlock_special load */ |
Paul E. McKenney | 1d082fd | 2014-08-14 16:01:53 -0700 | [diff] [blame] | 153 | if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special.s))) |
Paul E. McKenney | 2a3fa84 | 2012-05-21 11:58:36 -0700 | [diff] [blame] | 154 | rcu_read_unlock_special(t); |
| 155 | barrier(); /* ->rcu_read_unlock_special load before assign */ |
| 156 | t->rcu_read_lock_nesting = 0; |
| 157 | } |
| 158 | #ifdef CONFIG_PROVE_LOCKING |
| 159 | { |
| 160 | int rrln = ACCESS_ONCE(t->rcu_read_lock_nesting); |
| 161 | |
| 162 | WARN_ON_ONCE(rrln < 0 && rrln > INT_MIN / 2); |
| 163 | } |
| 164 | #endif /* #ifdef CONFIG_PROVE_LOCKING */ |
| 165 | } |
| 166 | EXPORT_SYMBOL_GPL(__rcu_read_unlock); |
| 167 | |
Paul E. McKenney | 2439b69 | 2013-04-11 10:15:52 -0700 | [diff] [blame] | 168 | #endif /* #ifdef CONFIG_PREEMPT_RCU */ |
Paul E. McKenney | 9dd8fb1 | 2012-04-13 12:54:22 -0700 | [diff] [blame] | 169 | |
Paul E. McKenney | 162cc27 | 2009-09-23 16:18:13 -0700 | [diff] [blame] | 170 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 171 | static struct lock_class_key rcu_lock_key; |
| 172 | struct lockdep_map rcu_lock_map = |
| 173 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key); |
| 174 | EXPORT_SYMBOL_GPL(rcu_lock_map); |
Paul E. McKenney | 632ee20 | 2010-02-22 17:04:45 -0800 | [diff] [blame] | 175 | |
| 176 | static struct lock_class_key rcu_bh_lock_key; |
| 177 | struct lockdep_map rcu_bh_lock_map = |
| 178 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key); |
| 179 | EXPORT_SYMBOL_GPL(rcu_bh_lock_map); |
| 180 | |
| 181 | static struct lock_class_key rcu_sched_lock_key; |
| 182 | struct lockdep_map rcu_sched_lock_map = |
| 183 | STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key); |
| 184 | EXPORT_SYMBOL_GPL(rcu_sched_lock_map); |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 185 | |
Paul E. McKenney | 24ef659 | 2013-10-28 09:22:24 -0700 | [diff] [blame] | 186 | static struct lock_class_key rcu_callback_key; |
| 187 | struct lockdep_map rcu_callback_map = |
| 188 | STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key); |
| 189 | EXPORT_SYMBOL_GPL(rcu_callback_map); |
| 190 | |
Steven Rostedt (Red Hat) | a0a5a05 | 2013-08-31 01:04:07 -0400 | [diff] [blame] | 191 | int notrace debug_lockdep_rcu_enabled(void) |
Paul E. McKenney | bc293d6 | 2010-04-15 12:50:39 -0700 | [diff] [blame] | 192 | { |
| 193 | return rcu_scheduler_active && debug_locks && |
| 194 | current->lockdep_recursion == 0; |
| 195 | } |
| 196 | EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled); |
| 197 | |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 198 | /** |
Oleg Nesterov | 85b39d3 | 2014-07-08 15:17:59 -0700 | [diff] [blame] | 199 | * rcu_read_lock_held() - might we be in RCU read-side critical section? |
| 200 | * |
| 201 | * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU |
| 202 | * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, |
| 203 | * this assumes we are in an RCU read-side critical section unless it can |
| 204 | * prove otherwise. This is useful for debug checks in functions that |
| 205 | * require that they be called within an RCU read-side critical section. |
| 206 | * |
| 207 | * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot |
| 208 | * and while lockdep is disabled. |
| 209 | * |
| 210 | * Note that rcu_read_lock() and the matching rcu_read_unlock() must |
| 211 | * occur in the same context, for example, it is illegal to invoke |
| 212 | * rcu_read_unlock() in process context if the matching rcu_read_lock() |
| 213 | * was invoked from within an irq handler. |
| 214 | * |
| 215 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or |
| 216 | * offline from an RCU perspective, so check for those as well. |
| 217 | */ |
| 218 | int rcu_read_lock_held(void) |
| 219 | { |
| 220 | if (!debug_lockdep_rcu_enabled()) |
| 221 | return 1; |
| 222 | if (!rcu_is_watching()) |
| 223 | return 0; |
| 224 | if (!rcu_lockdep_current_cpu_online()) |
| 225 | return 0; |
| 226 | return lock_is_held(&rcu_lock_map); |
| 227 | } |
| 228 | EXPORT_SYMBOL_GPL(rcu_read_lock_held); |
| 229 | |
| 230 | /** |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 231 | * rcu_read_lock_bh_held() - might we be in RCU-bh read-side critical section? |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 232 | * |
| 233 | * Check for bottom half being disabled, which covers both the |
| 234 | * CONFIG_PROVE_RCU and not cases. Note that if someone uses |
| 235 | * rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled) |
Paul E. McKenney | ca5ecdd | 2010-04-28 14:39:09 -0700 | [diff] [blame] | 236 | * will show the situation. This is useful for debug checks in functions |
| 237 | * that require that they be called within an RCU read-side critical |
| 238 | * section. |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 239 | * |
| 240 | * Check debug_lockdep_rcu_enabled() to prevent false positives during boot. |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 241 | * |
| 242 | * Note that rcu_read_lock() is disallowed if the CPU is either idle or |
| 243 | * offline from an RCU perspective, so check for those as well. |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 244 | */ |
| 245 | int rcu_read_lock_bh_held(void) |
| 246 | { |
| 247 | if (!debug_lockdep_rcu_enabled()) |
| 248 | return 1; |
Paul E. McKenney | 5c173eb | 2013-09-13 17:20:11 -0700 | [diff] [blame] | 249 | if (!rcu_is_watching()) |
Frederic Weisbecker | e6b80a3 | 2011-10-07 16:25:18 -0700 | [diff] [blame] | 250 | return 0; |
Paul E. McKenney | c0d6d01 | 2012-01-23 12:41:26 -0800 | [diff] [blame] | 251 | if (!rcu_lockdep_current_cpu_online()) |
| 252 | return 0; |
Paul E. McKenney | 773e3f9 | 2010-10-05 14:03:02 -0700 | [diff] [blame] | 253 | return in_softirq() || irqs_disabled(); |
Paul E. McKenney | e3818b8 | 2010-03-15 17:03:43 -0700 | [diff] [blame] | 254 | } |
| 255 | EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); |
| 256 | |
| 257 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 258 | |
Paul E. McKenney | ee376db | 2015-01-10 19:47:10 -0800 | [diff] [blame] | 259 | /** |
| 260 | * wakeme_after_rcu() - Callback function to awaken a task after grace period |
| 261 | * @head: Pointer to rcu_head member within rcu_synchronize structure |
| 262 | * |
| 263 | * Awaken the corresponding task now that a grace period has elapsed. |
Paul E. McKenney | fbf6bfc | 2008-02-13 15:03:15 -0800 | [diff] [blame] | 264 | */ |
Paul E. McKenney | ee376db | 2015-01-10 19:47:10 -0800 | [diff] [blame] | 265 | void wakeme_after_rcu(struct rcu_head *head) |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 266 | { |
Paul E. McKenney | 01c1c66 | 2008-01-25 21:08:24 +0100 | [diff] [blame] | 267 | struct rcu_synchronize *rcu; |
| 268 | |
| 269 | rcu = container_of(head, struct rcu_synchronize, head); |
| 270 | complete(&rcu->completion); |
Dipankar Sarma | 21a1ea9 | 2006-03-07 21:55:33 -0800 | [diff] [blame] | 271 | } |
Paul E. McKenney | ee84b82 | 2010-05-06 09:28:41 -0700 | [diff] [blame] | 272 | |
Paul E. McKenney | 2c42818 | 2011-05-26 22:14:36 -0700 | [diff] [blame] | 273 | void wait_rcu_gp(call_rcu_func_t crf) |
| 274 | { |
| 275 | struct rcu_synchronize rcu; |
| 276 | |
| 277 | init_rcu_head_on_stack(&rcu.head); |
| 278 | init_completion(&rcu.completion); |
| 279 | /* Will wake me after RCU finished. */ |
| 280 | crf(&rcu.head, wakeme_after_rcu); |
| 281 | /* Wait for it. */ |
| 282 | wait_for_completion(&rcu.completion); |
| 283 | destroy_rcu_head_on_stack(&rcu.head); |
| 284 | } |
| 285 | EXPORT_SYMBOL_GPL(wait_rcu_gp); |
| 286 | |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 287 | #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD |
Paul E. McKenney | 546a9d8 | 2014-06-19 14:57:10 -0700 | [diff] [blame] | 288 | void init_rcu_head(struct rcu_head *head) |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 289 | { |
| 290 | debug_object_init(head, &rcuhead_debug_descr); |
| 291 | } |
| 292 | |
Paul E. McKenney | 546a9d8 | 2014-06-19 14:57:10 -0700 | [diff] [blame] | 293 | void destroy_rcu_head(struct rcu_head *head) |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 294 | { |
| 295 | debug_object_free(head, &rcuhead_debug_descr); |
| 296 | } |
| 297 | |
| 298 | /* |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 299 | * fixup_activate is called when: |
| 300 | * - an active object is activated |
| 301 | * - an unknown object is activated (might be a statically initialized object) |
| 302 | * Activation is performed internally by call_rcu(). |
| 303 | */ |
| 304 | static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state) |
| 305 | { |
| 306 | struct rcu_head *head = addr; |
| 307 | |
| 308 | switch (state) { |
| 309 | |
| 310 | case ODEBUG_STATE_NOTAVAILABLE: |
| 311 | /* |
| 312 | * This is not really a fixup. We just make sure that it is |
| 313 | * tracked in the object tracker. |
| 314 | */ |
| 315 | debug_object_init(head, &rcuhead_debug_descr); |
| 316 | debug_object_activate(head, &rcuhead_debug_descr); |
| 317 | return 0; |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 318 | default: |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 319 | return 1; |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 320 | } |
| 321 | } |
| 322 | |
| 323 | /** |
| 324 | * init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects |
| 325 | * @head: pointer to rcu_head structure to be initialized |
| 326 | * |
| 327 | * This function informs debugobjects of a new rcu_head structure that |
| 328 | * has been allocated as an auto variable on the stack. This function |
| 329 | * is not required for rcu_head structures that are statically defined or |
| 330 | * that are dynamically allocated on the heap. This function has no |
| 331 | * effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
| 332 | */ |
| 333 | void init_rcu_head_on_stack(struct rcu_head *head) |
| 334 | { |
| 335 | debug_object_init_on_stack(head, &rcuhead_debug_descr); |
| 336 | } |
| 337 | EXPORT_SYMBOL_GPL(init_rcu_head_on_stack); |
| 338 | |
| 339 | /** |
| 340 | * destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects |
| 341 | * @head: pointer to rcu_head structure to be initialized |
| 342 | * |
| 343 | * This function informs debugobjects that an on-stack rcu_head structure |
| 344 | * is about to go out of scope. As with init_rcu_head_on_stack(), this |
| 345 | * function is not required for rcu_head structures that are statically |
| 346 | * defined or that are dynamically allocated on the heap. Also as with |
| 347 | * init_rcu_head_on_stack(), this function has no effect for |
| 348 | * !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds. |
| 349 | */ |
| 350 | void destroy_rcu_head_on_stack(struct rcu_head *head) |
| 351 | { |
| 352 | debug_object_free(head, &rcuhead_debug_descr); |
| 353 | } |
| 354 | EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack); |
| 355 | |
| 356 | struct debug_obj_descr rcuhead_debug_descr = { |
| 357 | .name = "rcu_head", |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 358 | .fixup_activate = rcuhead_fixup_activate, |
Mathieu Desnoyers | 551d55a | 2010-04-17 08:48:42 -0400 | [diff] [blame] | 359 | }; |
| 360 | EXPORT_SYMBOL_GPL(rcuhead_debug_descr); |
| 361 | #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 362 | |
Pranith Kumar | 28f6569 | 2014-09-22 14:00:48 -0400 | [diff] [blame] | 363 | #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE) |
Steven Rostedt (Red Hat) | e66c33d | 2013-07-12 16:50:28 -0400 | [diff] [blame] | 364 | void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, |
Paul E. McKenney | 5249453 | 2012-11-14 16:26:40 -0800 | [diff] [blame] | 365 | unsigned long secs, |
| 366 | unsigned long c_old, unsigned long c) |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 367 | { |
Paul E. McKenney | 5249453 | 2012-11-14 16:26:40 -0800 | [diff] [blame] | 368 | trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c); |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 369 | } |
| 370 | EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); |
| 371 | #else |
Paul E. McKenney | 5249453 | 2012-11-14 16:26:40 -0800 | [diff] [blame] | 372 | #define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ |
| 373 | do { } while (0) |
Paul E. McKenney | 91afaf3 | 2011-10-02 07:44:32 -0700 | [diff] [blame] | 374 | #endif |
Paul E. McKenney | 6bfc09e | 2012-10-19 12:49:17 -0700 | [diff] [blame] | 375 | |
| 376 | #ifdef CONFIG_RCU_STALL_COMMON |
| 377 | |
| 378 | #ifdef CONFIG_PROVE_RCU |
| 379 | #define RCU_STALL_DELAY_DELTA (5 * HZ) |
| 380 | #else |
| 381 | #define RCU_STALL_DELAY_DELTA 0 |
| 382 | #endif |
| 383 | |
| 384 | int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ |
Paul E. McKenney | 01896f7 | 2013-08-18 12:14:32 -0700 | [diff] [blame] | 385 | static int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; |
Paul E. McKenney | 6bfc09e | 2012-10-19 12:49:17 -0700 | [diff] [blame] | 386 | |
| 387 | module_param(rcu_cpu_stall_suppress, int, 0644); |
| 388 | module_param(rcu_cpu_stall_timeout, int, 0644); |
| 389 | |
| 390 | int rcu_jiffies_till_stall_check(void) |
| 391 | { |
| 392 | int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout); |
| 393 | |
| 394 | /* |
| 395 | * Limit check must be consistent with the Kconfig limits |
| 396 | * for CONFIG_RCU_CPU_STALL_TIMEOUT. |
| 397 | */ |
| 398 | if (till_stall_check < 3) { |
| 399 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 3; |
| 400 | till_stall_check = 3; |
| 401 | } else if (till_stall_check > 300) { |
| 402 | ACCESS_ONCE(rcu_cpu_stall_timeout) = 300; |
| 403 | till_stall_check = 300; |
| 404 | } |
| 405 | return till_stall_check * HZ + RCU_STALL_DELAY_DELTA; |
| 406 | } |
| 407 | |
Rik van Riel | 61f38db | 2014-04-26 23:15:35 -0700 | [diff] [blame] | 408 | void rcu_sysrq_start(void) |
| 409 | { |
| 410 | if (!rcu_cpu_stall_suppress) |
| 411 | rcu_cpu_stall_suppress = 2; |
| 412 | } |
| 413 | |
| 414 | void rcu_sysrq_end(void) |
| 415 | { |
| 416 | if (rcu_cpu_stall_suppress == 2) |
| 417 | rcu_cpu_stall_suppress = 0; |
| 418 | } |
| 419 | |
Paul E. McKenney | 6bfc09e | 2012-10-19 12:49:17 -0700 | [diff] [blame] | 420 | static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) |
| 421 | { |
| 422 | rcu_cpu_stall_suppress = 1; |
| 423 | return NOTIFY_DONE; |
| 424 | } |
| 425 | |
| 426 | static struct notifier_block rcu_panic_block = { |
| 427 | .notifier_call = rcu_panic, |
| 428 | }; |
| 429 | |
| 430 | static int __init check_cpu_stall_init(void) |
| 431 | { |
| 432 | atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block); |
| 433 | return 0; |
| 434 | } |
| 435 | early_initcall(check_cpu_stall_init); |
| 436 | |
| 437 | #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 438 | |
| 439 | #ifdef CONFIG_TASKS_RCU |
| 440 | |
| 441 | /* |
| 442 | * Simple variant of RCU whose quiescent states are voluntary context switch, |
| 443 | * user-space execution, and idle. As such, grace periods can take one good |
| 444 | * long time. There are no read-side primitives similar to rcu_read_lock() |
| 445 | * and rcu_read_unlock() because this implementation is intended to get |
| 446 | * the system into a safe state for some of the manipulations involved in |
| 447 | * tracing and the like. Finally, this implementation does not support |
| 448 | * high call_rcu_tasks() rates from multiple CPUs. If this is required, |
| 449 | * per-CPU callback lists will be needed. |
| 450 | */ |
| 451 | |
| 452 | /* Global list of callbacks and associated lock. */ |
| 453 | static struct rcu_head *rcu_tasks_cbs_head; |
| 454 | static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; |
Paul E. McKenney | c7b24d2 | 2014-07-28 14:39:25 -0700 | [diff] [blame] | 455 | static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 456 | static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock); |
| 457 | |
Paul E. McKenney | 3f95aa8 | 2014-08-04 06:10:23 -0700 | [diff] [blame] | 458 | /* Track exiting tasks in order to allow them to be waited for. */ |
| 459 | DEFINE_SRCU(tasks_rcu_exit_srcu); |
| 460 | |
| 461 | /* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */ |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 462 | static int rcu_task_stall_timeout __read_mostly = HZ * 60 * 10; |
Paul E. McKenney | 3f95aa8 | 2014-08-04 06:10:23 -0700 | [diff] [blame] | 463 | module_param(rcu_task_stall_timeout, int, 0644); |
| 464 | |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 465 | static void rcu_spawn_tasks_kthread(void); |
| 466 | |
| 467 | /* |
| 468 | * Post an RCU-tasks callback. First call must be from process context |
| 469 | * after the scheduler if fully operational. |
| 470 | */ |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 471 | void call_rcu_tasks(struct rcu_head *rhp, void (*func)(struct rcu_head *rhp)) |
| 472 | { |
| 473 | unsigned long flags; |
Paul E. McKenney | c7b24d2 | 2014-07-28 14:39:25 -0700 | [diff] [blame] | 474 | bool needwake; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 475 | |
| 476 | rhp->next = NULL; |
| 477 | rhp->func = func; |
| 478 | raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); |
Paul E. McKenney | c7b24d2 | 2014-07-28 14:39:25 -0700 | [diff] [blame] | 479 | needwake = !rcu_tasks_cbs_head; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 480 | *rcu_tasks_cbs_tail = rhp; |
| 481 | rcu_tasks_cbs_tail = &rhp->next; |
| 482 | raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 483 | if (needwake) { |
| 484 | rcu_spawn_tasks_kthread(); |
Paul E. McKenney | c7b24d2 | 2014-07-28 14:39:25 -0700 | [diff] [blame] | 485 | wake_up(&rcu_tasks_cbs_wq); |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 486 | } |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 487 | } |
| 488 | EXPORT_SYMBOL_GPL(call_rcu_tasks); |
| 489 | |
Paul E. McKenney | 53c6d4e | 2014-07-01 12:22:23 -0700 | [diff] [blame] | 490 | /** |
| 491 | * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed. |
| 492 | * |
| 493 | * Control will return to the caller some time after a full rcu-tasks |
| 494 | * grace period has elapsed, in other words after all currently |
| 495 | * executing rcu-tasks read-side critical sections have elapsed. These |
| 496 | * read-side critical sections are delimited by calls to schedule(), |
| 497 | * cond_resched_rcu_qs(), idle execution, userspace execution, calls |
| 498 | * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched(). |
| 499 | * |
| 500 | * This is a very specialized primitive, intended only for a few uses in |
| 501 | * tracing and other situations requiring manipulation of function |
| 502 | * preambles and profiling hooks. The synchronize_rcu_tasks() function |
| 503 | * is not (yet) intended for heavy use from multiple CPUs. |
| 504 | * |
| 505 | * Note that this guarantee implies further memory-ordering guarantees. |
| 506 | * On systems with more than one CPU, when synchronize_rcu_tasks() returns, |
| 507 | * each CPU is guaranteed to have executed a full memory barrier since the |
| 508 | * end of its last RCU-tasks read-side critical section whose beginning |
| 509 | * preceded the call to synchronize_rcu_tasks(). In addition, each CPU |
| 510 | * having an RCU-tasks read-side critical section that extends beyond |
| 511 | * the return from synchronize_rcu_tasks() is guaranteed to have executed |
| 512 | * a full memory barrier after the beginning of synchronize_rcu_tasks() |
| 513 | * and before the beginning of that RCU-tasks read-side critical section. |
| 514 | * Note that these guarantees include CPUs that are offline, idle, or |
| 515 | * executing in user mode, as well as CPUs that are executing in the kernel. |
| 516 | * |
| 517 | * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned |
| 518 | * to its caller on CPU B, then both CPU A and CPU B are guaranteed |
| 519 | * to have executed a full memory barrier during the execution of |
| 520 | * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU |
| 521 | * (but again only if the system has more than one CPU). |
| 522 | */ |
| 523 | void synchronize_rcu_tasks(void) |
| 524 | { |
| 525 | /* Complain if the scheduler has not started. */ |
| 526 | rcu_lockdep_assert(!rcu_scheduler_active, |
| 527 | "synchronize_rcu_tasks called too soon"); |
| 528 | |
| 529 | /* Wait for the grace period. */ |
| 530 | wait_rcu_gp(call_rcu_tasks); |
| 531 | } |
Steven Rostedt | 06c2a92 | 2014-07-02 18:17:19 -0700 | [diff] [blame] | 532 | EXPORT_SYMBOL_GPL(synchronize_rcu_tasks); |
Paul E. McKenney | 53c6d4e | 2014-07-01 12:22:23 -0700 | [diff] [blame] | 533 | |
| 534 | /** |
| 535 | * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks. |
| 536 | * |
| 537 | * Although the current implementation is guaranteed to wait, it is not |
| 538 | * obligated to, for example, if there are no pending callbacks. |
| 539 | */ |
| 540 | void rcu_barrier_tasks(void) |
| 541 | { |
| 542 | /* There is only one callback queue, so this is easy. ;-) */ |
| 543 | synchronize_rcu_tasks(); |
| 544 | } |
Steven Rostedt | 06c2a92 | 2014-07-02 18:17:19 -0700 | [diff] [blame] | 545 | EXPORT_SYMBOL_GPL(rcu_barrier_tasks); |
Paul E. McKenney | 53c6d4e | 2014-07-01 12:22:23 -0700 | [diff] [blame] | 546 | |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 547 | /* See if tasks are still holding out, complain if so. */ |
| 548 | static void check_holdout_task(struct task_struct *t, |
| 549 | bool needreport, bool *firstreport) |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 550 | { |
Paul E. McKenney | 4ff475e | 2014-08-10 19:47:12 -0700 | [diff] [blame] | 551 | int cpu; |
| 552 | |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 553 | if (!ACCESS_ONCE(t->rcu_tasks_holdout) || |
| 554 | t->rcu_tasks_nvcsw != ACCESS_ONCE(t->nvcsw) || |
Paul E. McKenney | 176f8f7 | 2014-08-04 17:43:50 -0700 | [diff] [blame] | 555 | !ACCESS_ONCE(t->on_rq) || |
| 556 | (IS_ENABLED(CONFIG_NO_HZ_FULL) && |
| 557 | !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) { |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 558 | ACCESS_ONCE(t->rcu_tasks_holdout) = false; |
Paul E. McKenney | 8f20a5e | 2014-08-05 05:10:24 -0700 | [diff] [blame] | 559 | list_del_init(&t->rcu_tasks_holdout_list); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 560 | put_task_struct(t); |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 561 | return; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 562 | } |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 563 | if (!needreport) |
| 564 | return; |
| 565 | if (*firstreport) { |
| 566 | pr_err("INFO: rcu_tasks detected stalls on tasks:\n"); |
| 567 | *firstreport = false; |
| 568 | } |
Paul E. McKenney | 4ff475e | 2014-08-10 19:47:12 -0700 | [diff] [blame] | 569 | cpu = task_cpu(t); |
| 570 | pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n", |
| 571 | t, ".I"[is_idle_task(t)], |
| 572 | "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)], |
| 573 | t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout, |
| 574 | t->rcu_tasks_idle_cpu, cpu); |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 575 | sched_show_task(t); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 576 | } |
| 577 | |
| 578 | /* RCU-tasks kthread that detects grace periods and invokes callbacks. */ |
| 579 | static int __noreturn rcu_tasks_kthread(void *arg) |
| 580 | { |
| 581 | unsigned long flags; |
| 582 | struct task_struct *g, *t; |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 583 | unsigned long lastreport; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 584 | struct rcu_head *list; |
| 585 | struct rcu_head *next; |
| 586 | LIST_HEAD(rcu_tasks_holdouts); |
| 587 | |
Paul E. McKenney | 60ced49 | 2014-10-27 16:04:35 -0700 | [diff] [blame] | 588 | /* Run on housekeeping CPUs by default. Sysadm can move if desired. */ |
| 589 | housekeeping_affine(current); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 590 | |
| 591 | /* |
| 592 | * Each pass through the following loop makes one check for |
| 593 | * newly arrived callbacks, and, if there are some, waits for |
| 594 | * one RCU-tasks grace period and then invokes the callbacks. |
| 595 | * This loop is terminated by the system going down. ;-) |
| 596 | */ |
| 597 | for (;;) { |
| 598 | |
| 599 | /* Pick up any new callbacks. */ |
| 600 | raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); |
| 601 | list = rcu_tasks_cbs_head; |
| 602 | rcu_tasks_cbs_head = NULL; |
| 603 | rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; |
| 604 | raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); |
| 605 | |
| 606 | /* If there were none, wait a bit and start over. */ |
| 607 | if (!list) { |
Paul E. McKenney | c7b24d2 | 2014-07-28 14:39:25 -0700 | [diff] [blame] | 608 | wait_event_interruptible(rcu_tasks_cbs_wq, |
| 609 | rcu_tasks_cbs_head); |
| 610 | if (!rcu_tasks_cbs_head) { |
| 611 | WARN_ON(signal_pending(current)); |
| 612 | schedule_timeout_interruptible(HZ/10); |
| 613 | } |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 614 | continue; |
| 615 | } |
| 616 | |
| 617 | /* |
| 618 | * Wait for all pre-existing t->on_rq and t->nvcsw |
| 619 | * transitions to complete. Invoking synchronize_sched() |
| 620 | * suffices because all these transitions occur with |
| 621 | * interrupts disabled. Without this synchronize_sched(), |
| 622 | * a read-side critical section that started before the |
| 623 | * grace period might be incorrectly seen as having started |
| 624 | * after the grace period. |
| 625 | * |
| 626 | * This synchronize_sched() also dispenses with the |
| 627 | * need for a memory barrier on the first store to |
| 628 | * ->rcu_tasks_holdout, as it forces the store to happen |
| 629 | * after the beginning of the grace period. |
| 630 | */ |
| 631 | synchronize_sched(); |
| 632 | |
| 633 | /* |
| 634 | * There were callbacks, so we need to wait for an |
| 635 | * RCU-tasks grace period. Start off by scanning |
| 636 | * the task list for tasks that are not already |
| 637 | * voluntarily blocked. Mark these tasks and make |
| 638 | * a list of them in rcu_tasks_holdouts. |
| 639 | */ |
| 640 | rcu_read_lock(); |
| 641 | for_each_process_thread(g, t) { |
| 642 | if (t != current && ACCESS_ONCE(t->on_rq) && |
| 643 | !is_idle_task(t)) { |
| 644 | get_task_struct(t); |
| 645 | t->rcu_tasks_nvcsw = ACCESS_ONCE(t->nvcsw); |
| 646 | ACCESS_ONCE(t->rcu_tasks_holdout) = true; |
| 647 | list_add(&t->rcu_tasks_holdout_list, |
| 648 | &rcu_tasks_holdouts); |
| 649 | } |
| 650 | } |
| 651 | rcu_read_unlock(); |
| 652 | |
| 653 | /* |
Paul E. McKenney | 3f95aa8 | 2014-08-04 06:10:23 -0700 | [diff] [blame] | 654 | * Wait for tasks that are in the process of exiting. |
| 655 | * This does only part of the job, ensuring that all |
| 656 | * tasks that were previously exiting reach the point |
| 657 | * where they have disabled preemption, allowing the |
| 658 | * later synchronize_sched() to finish the job. |
| 659 | */ |
| 660 | synchronize_srcu(&tasks_rcu_exit_srcu); |
| 661 | |
| 662 | /* |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 663 | * Each pass through the following loop scans the list |
| 664 | * of holdout tasks, removing any that are no longer |
| 665 | * holdouts. When the list is empty, we are done. |
| 666 | */ |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 667 | lastreport = jiffies; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 668 | while (!list_empty(&rcu_tasks_holdouts)) { |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 669 | bool firstreport; |
| 670 | bool needreport; |
| 671 | int rtst; |
Paul E. McKenney | 8f20a5e | 2014-08-05 05:10:24 -0700 | [diff] [blame] | 672 | struct task_struct *t1; |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 673 | |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 674 | schedule_timeout_interruptible(HZ); |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 675 | rtst = ACCESS_ONCE(rcu_task_stall_timeout); |
| 676 | needreport = rtst > 0 && |
| 677 | time_after(jiffies, lastreport + rtst); |
| 678 | if (needreport) |
| 679 | lastreport = jiffies; |
| 680 | firstreport = true; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 681 | WARN_ON(signal_pending(current)); |
Paul E. McKenney | 8f20a5e | 2014-08-05 05:10:24 -0700 | [diff] [blame] | 682 | list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts, |
| 683 | rcu_tasks_holdout_list) { |
Paul E. McKenney | 52db30a | 2014-07-01 18:16:30 -0700 | [diff] [blame] | 684 | check_holdout_task(t, needreport, &firstreport); |
Paul E. McKenney | 8f20a5e | 2014-08-05 05:10:24 -0700 | [diff] [blame] | 685 | cond_resched(); |
| 686 | } |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 687 | } |
| 688 | |
| 689 | /* |
| 690 | * Because ->on_rq and ->nvcsw are not guaranteed |
| 691 | * to have a full memory barriers prior to them in the |
| 692 | * schedule() path, memory reordering on other CPUs could |
| 693 | * cause their RCU-tasks read-side critical sections to |
| 694 | * extend past the end of the grace period. However, |
| 695 | * because these ->nvcsw updates are carried out with |
| 696 | * interrupts disabled, we can use synchronize_sched() |
| 697 | * to force the needed ordering on all such CPUs. |
| 698 | * |
| 699 | * This synchronize_sched() also confines all |
| 700 | * ->rcu_tasks_holdout accesses to be within the grace |
| 701 | * period, avoiding the need for memory barriers for |
| 702 | * ->rcu_tasks_holdout accesses. |
Paul E. McKenney | 3f95aa8 | 2014-08-04 06:10:23 -0700 | [diff] [blame] | 703 | * |
| 704 | * In addition, this synchronize_sched() waits for exiting |
| 705 | * tasks to complete their final preempt_disable() region |
| 706 | * of execution, cleaning up after the synchronize_srcu() |
| 707 | * above. |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 708 | */ |
| 709 | synchronize_sched(); |
| 710 | |
| 711 | /* Invoke the callbacks. */ |
| 712 | while (list) { |
| 713 | next = list->next; |
| 714 | local_bh_disable(); |
| 715 | list->func(list); |
| 716 | local_bh_enable(); |
| 717 | list = next; |
| 718 | cond_resched(); |
| 719 | } |
Paul E. McKenney | c7b24d2 | 2014-07-28 14:39:25 -0700 | [diff] [blame] | 720 | schedule_timeout_uninterruptible(HZ/10); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 721 | } |
| 722 | } |
| 723 | |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 724 | /* Spawn rcu_tasks_kthread() at first call to call_rcu_tasks(). */ |
| 725 | static void rcu_spawn_tasks_kthread(void) |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 726 | { |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 727 | static DEFINE_MUTEX(rcu_tasks_kthread_mutex); |
| 728 | static struct task_struct *rcu_tasks_kthread_ptr; |
| 729 | struct task_struct *t; |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 730 | |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 731 | if (ACCESS_ONCE(rcu_tasks_kthread_ptr)) { |
| 732 | smp_mb(); /* Ensure caller sees full kthread. */ |
| 733 | return; |
| 734 | } |
| 735 | mutex_lock(&rcu_tasks_kthread_mutex); |
| 736 | if (rcu_tasks_kthread_ptr) { |
| 737 | mutex_unlock(&rcu_tasks_kthread_mutex); |
| 738 | return; |
| 739 | } |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 740 | t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread"); |
| 741 | BUG_ON(IS_ERR(t)); |
Paul E. McKenney | 84a8f44 | 2014-08-04 07:24:21 -0700 | [diff] [blame] | 742 | smp_mb(); /* Ensure others see full kthread. */ |
| 743 | ACCESS_ONCE(rcu_tasks_kthread_ptr) = t; |
| 744 | mutex_unlock(&rcu_tasks_kthread_mutex); |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 745 | } |
Paul E. McKenney | 8315f42 | 2014-06-27 13:42:20 -0700 | [diff] [blame] | 746 | |
| 747 | #endif /* #ifdef CONFIG_TASKS_RCU */ |
Pranith Kumar | aa23c6fbc | 2014-09-19 11:32:29 -0400 | [diff] [blame] | 748 | |
| 749 | #ifdef CONFIG_PROVE_RCU |
| 750 | |
| 751 | /* |
| 752 | * Early boot self test parameters, one for each flavor |
| 753 | */ |
| 754 | static bool rcu_self_test; |
| 755 | static bool rcu_self_test_bh; |
| 756 | static bool rcu_self_test_sched; |
| 757 | |
| 758 | module_param(rcu_self_test, bool, 0444); |
| 759 | module_param(rcu_self_test_bh, bool, 0444); |
| 760 | module_param(rcu_self_test_sched, bool, 0444); |
| 761 | |
| 762 | static int rcu_self_test_counter; |
| 763 | |
| 764 | static void test_callback(struct rcu_head *r) |
| 765 | { |
| 766 | rcu_self_test_counter++; |
| 767 | pr_info("RCU test callback executed %d\n", rcu_self_test_counter); |
| 768 | } |
| 769 | |
| 770 | static void early_boot_test_call_rcu(void) |
| 771 | { |
| 772 | static struct rcu_head head; |
| 773 | |
| 774 | call_rcu(&head, test_callback); |
| 775 | } |
| 776 | |
| 777 | static void early_boot_test_call_rcu_bh(void) |
| 778 | { |
| 779 | static struct rcu_head head; |
| 780 | |
| 781 | call_rcu_bh(&head, test_callback); |
| 782 | } |
| 783 | |
| 784 | static void early_boot_test_call_rcu_sched(void) |
| 785 | { |
| 786 | static struct rcu_head head; |
| 787 | |
| 788 | call_rcu_sched(&head, test_callback); |
| 789 | } |
| 790 | |
| 791 | void rcu_early_boot_tests(void) |
| 792 | { |
| 793 | pr_info("Running RCU self tests\n"); |
| 794 | |
| 795 | if (rcu_self_test) |
| 796 | early_boot_test_call_rcu(); |
| 797 | if (rcu_self_test_bh) |
| 798 | early_boot_test_call_rcu_bh(); |
| 799 | if (rcu_self_test_sched) |
| 800 | early_boot_test_call_rcu_sched(); |
| 801 | } |
| 802 | |
| 803 | static int rcu_verify_early_boot_tests(void) |
| 804 | { |
| 805 | int ret = 0; |
| 806 | int early_boot_test_counter = 0; |
| 807 | |
| 808 | if (rcu_self_test) { |
| 809 | early_boot_test_counter++; |
| 810 | rcu_barrier(); |
| 811 | } |
| 812 | if (rcu_self_test_bh) { |
| 813 | early_boot_test_counter++; |
| 814 | rcu_barrier_bh(); |
| 815 | } |
| 816 | if (rcu_self_test_sched) { |
| 817 | early_boot_test_counter++; |
| 818 | rcu_barrier_sched(); |
| 819 | } |
| 820 | |
| 821 | if (rcu_self_test_counter != early_boot_test_counter) { |
| 822 | WARN_ON(1); |
| 823 | ret = -1; |
| 824 | } |
| 825 | |
| 826 | return ret; |
| 827 | } |
| 828 | late_initcall(rcu_verify_early_boot_tests); |
| 829 | #else |
| 830 | void rcu_early_boot_tests(void) {} |
| 831 | #endif /* CONFIG_PROVE_RCU */ |