1/* SPDX-License-Identifier: GPL-2.0+ */ 2/* 3 * Sleepable Read-Copy Update mechanism for mutual exclusion 4 * 5 * Copyright (C) IBM Corporation, 2006 6 * Copyright (C) Fujitsu, 2012 7 * 8 * Author: Paul McKenney <paulmck@linux.ibm.com> 9 * Lai Jiangshan <laijs@cn.fujitsu.com> 10 * 11 * For detailed explanation of Read-Copy Update mechanism see - 12 * Documentation/RCU/ *.txt 13 * 14 */ 15 16#ifndef _LINUX_SRCU_H 17#define _LINUX_SRCU_H 18 19#include <linux/mutex.h> 20#include <linux/rcupdate.h> 21#include <linux/workqueue.h> 22#include <linux/rcu_segcblist.h> 23 24struct srcu_struct; 25 26#ifdef CONFIG_DEBUG_LOCK_ALLOC 27 28int __init_srcu_struct(struct srcu_struct *ssp, const char *name, 29 struct lock_class_key *key); 30 31#define init_srcu_struct(ssp) \ 32({ \ 33 static struct lock_class_key __srcu_key; \ 34 \ 35 __init_srcu_struct((ssp), #ssp, &__srcu_key); \ 36}) 37 38#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, 39#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 40 41int init_srcu_struct(struct srcu_struct *ssp); 42 43#define __SRCU_DEP_MAP_INIT(srcu_name) 44#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 45 46#ifdef CONFIG_TINY_SRCU 47#include <linux/srcutiny.h> 48#elif defined(CONFIG_TREE_SRCU) 49#include <linux/srcutree.h> 50#else 51#error "Unknown SRCU implementation specified to kernel configuration" 52#endif 53 54void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, 55 void (*func)(struct rcu_head *head)); 56void cleanup_srcu_struct(struct srcu_struct *ssp); 57int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); 58void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); 59void synchronize_srcu(struct srcu_struct *ssp); 60unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); 61unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); 62bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); 63 64#ifdef CONFIG_NEED_SRCU_NMI_SAFE 65int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); 66void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); 67#else 68static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) 69{ 70 return __srcu_read_lock(ssp); 71} 72static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) 73{ 74 __srcu_read_unlock(ssp, idx); 75} 76#endif /* CONFIG_NEED_SRCU_NMI_SAFE */ 77 78void srcu_init(void); 79 80#ifdef CONFIG_DEBUG_LOCK_ALLOC 81 82/** 83 * srcu_read_lock_held - might we be in SRCU read-side critical section? 84 * @ssp: The srcu_struct structure to check 85 * 86 * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU 87 * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, 88 * this assumes we are in an SRCU read-side critical section unless it can 89 * prove otherwise. 90 * 91 * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot 92 * and while lockdep is disabled. 93 * 94 * Note that SRCU is based on its own statemachine and it doesn't 95 * relies on normal RCU, it can be called from the CPU which 96 * is in the idle loop from an RCU point of view or offline. 97 */ 98static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 99{ 100 if (!debug_lockdep_rcu_enabled()) 101 return 1; 102 return lock_is_held(&ssp->dep_map); 103} 104 105/* 106 * Annotations provide deadlock detection for SRCU. 107 * 108 * Similar to other lockdep annotations, except there is an additional 109 * srcu_lock_sync(), which is basically an empty *write*-side critical section, 110 * see lock_sync() for more information. 111 */ 112 113/* Annotates a srcu_read_lock() */ 114static inline void srcu_lock_acquire(struct lockdep_map *map) 115{ 116 lock_map_acquire_read(map); 117} 118 119/* Annotates a srcu_read_lock() */ 120static inline void srcu_lock_release(struct lockdep_map *map) 121{ 122 lock_map_release(map); 123} 124 125/* Annotates a synchronize_srcu() */ 126static inline void srcu_lock_sync(struct lockdep_map *map) 127{ 128 lock_map_sync(map); 129} 130 131#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 132 133static inline int srcu_read_lock_held(const struct srcu_struct *ssp) 134{ 135 return 1; 136} 137 138#define srcu_lock_acquire(m) do { } while (0) 139#define srcu_lock_release(m) do { } while (0) 140#define srcu_lock_sync(m) do { } while (0) 141 142#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 143 144#define SRCU_NMI_UNKNOWN 0x0 145#define SRCU_NMI_UNSAFE 0x1 146#define SRCU_NMI_SAFE 0x2 147 148#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) 149void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); 150#else 151static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, 152 bool nmi_safe) { } 153#endif 154 155 156/** 157 * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing 158 * @p: the pointer to fetch and protect for later dereferencing 159 * @ssp: pointer to the srcu_struct, which is used to check that we 160 * really are in an SRCU read-side critical section. 161 * @c: condition to check for update-side use 162 * 163 * If PROVE_RCU is enabled, invoking this outside of an RCU read-side 164 * critical section will result in an RCU-lockdep splat, unless @c evaluates 165 * to 1. The @c argument will normally be a logical expression containing 166 * lockdep_is_held() calls. 167 */ 168#define srcu_dereference_check(p, ssp, c) \ 169 __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ 170 (c) || srcu_read_lock_held(ssp), __rcu) 171 172/** 173 * srcu_dereference - fetch SRCU-protected pointer for later dereferencing 174 * @p: the pointer to fetch and protect for later dereferencing 175 * @ssp: pointer to the srcu_struct, which is used to check that we 176 * really are in an SRCU read-side critical section. 177 * 178 * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU 179 * is enabled, invoking this outside of an RCU read-side critical 180 * section will result in an RCU-lockdep splat. 181 */ 182#define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) 183 184/** 185 * srcu_dereference_notrace - no tracing and no lockdep calls from here 186 * @p: the pointer to fetch and protect for later dereferencing 187 * @ssp: pointer to the srcu_struct, which is used to check that we 188 * really are in an SRCU read-side critical section. 189 */ 190#define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) 191 192/** 193 * srcu_read_lock - register a new reader for an SRCU-protected structure. 194 * @ssp: srcu_struct in which to register the new reader. 195 * 196 * Enter an SRCU read-side critical section. Note that SRCU read-side 197 * critical sections may be nested. However, it is illegal to 198 * call anything that waits on an SRCU grace period for the same 199 * srcu_struct, whether directly or indirectly. Please note that 200 * one way to indirectly wait on an SRCU grace period is to acquire 201 * a mutex that is held elsewhere while calling synchronize_srcu() or 202 * synchronize_srcu_expedited(). 203 * 204 * Note that srcu_read_lock() and the matching srcu_read_unlock() must 205 * occur in the same context, for example, it is illegal to invoke 206 * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() 207 * was invoked in process context. 208 */ 209static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) 210{ 211 int retval; 212 213 srcu_check_nmi_safety(ssp, false); 214 retval = __srcu_read_lock(ssp); 215 srcu_lock_acquire(&ssp->dep_map); 216 return retval; 217} 218 219/** 220 * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure. 221 * @ssp: srcu_struct in which to register the new reader. 222 * 223 * Enter an SRCU read-side critical section, but in an NMI-safe manner. 224 * See srcu_read_lock() for more information. 225 */ 226static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp) 227{ 228 int retval; 229 230 srcu_check_nmi_safety(ssp, true); 231 retval = __srcu_read_lock_nmisafe(ssp); 232 rcu_try_lock_acquire(&ssp->dep_map); 233 return retval; 234} 235 236/* Used by tracing, cannot be traced and cannot invoke lockdep. */ 237static inline notrace int 238srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) 239{ 240 int retval; 241 242 srcu_check_nmi_safety(ssp, false); 243 retval = __srcu_read_lock(ssp); 244 return retval; 245} 246 247/** 248 * srcu_down_read - register a new reader for an SRCU-protected structure. 249 * @ssp: srcu_struct in which to register the new reader. 250 * 251 * Enter a semaphore-like SRCU read-side critical section. Note that 252 * SRCU read-side critical sections may be nested. However, it is 253 * illegal to call anything that waits on an SRCU grace period for the 254 * same srcu_struct, whether directly or indirectly. Please note that 255 * one way to indirectly wait on an SRCU grace period is to acquire 256 * a mutex that is held elsewhere while calling synchronize_srcu() or 257 * synchronize_srcu_expedited(). But if you want lockdep to help you 258 * keep this stuff straight, you should instead use srcu_read_lock(). 259 * 260 * The semaphore-like nature of srcu_down_read() means that the matching 261 * srcu_up_read() can be invoked from some other context, for example, 262 * from some other task or from an irq handler. However, neither 263 * srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler. 264 * 265 * Calls to srcu_down_read() may be nested, similar to the manner in 266 * which calls to down_read() may be nested. 267 */ 268static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) 269{ 270 WARN_ON_ONCE(in_nmi()); 271 srcu_check_nmi_safety(ssp, false); 272 return __srcu_read_lock(ssp); 273} 274 275/** 276 * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. 277 * @ssp: srcu_struct in which to unregister the old reader. 278 * @idx: return value from corresponding srcu_read_lock(). 279 * 280 * Exit an SRCU read-side critical section. 281 */ 282static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) 283 __releases(ssp) 284{ 285 WARN_ON_ONCE(idx & ~0x1); 286 srcu_check_nmi_safety(ssp, false); 287 srcu_lock_release(&ssp->dep_map); 288 __srcu_read_unlock(ssp, idx); 289} 290 291/** 292 * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure. 293 * @ssp: srcu_struct in which to unregister the old reader. 294 * @idx: return value from corresponding srcu_read_lock(). 295 * 296 * Exit an SRCU read-side critical section, but in an NMI-safe manner. 297 */ 298static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) 299 __releases(ssp) 300{ 301 WARN_ON_ONCE(idx & ~0x1); 302 srcu_check_nmi_safety(ssp, true); 303 rcu_lock_release(&ssp->dep_map); 304 __srcu_read_unlock_nmisafe(ssp, idx); 305} 306 307/* Used by tracing, cannot be traced and cannot call lockdep. */ 308static inline notrace void 309srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) 310{ 311 srcu_check_nmi_safety(ssp, false); 312 __srcu_read_unlock(ssp, idx); 313} 314 315/** 316 * srcu_up_read - unregister a old reader from an SRCU-protected structure. 317 * @ssp: srcu_struct in which to unregister the old reader. 318 * @idx: return value from corresponding srcu_read_lock(). 319 * 320 * Exit an SRCU read-side critical section, but not necessarily from 321 * the same context as the maching srcu_down_read(). 322 */ 323static inline void srcu_up_read(struct srcu_struct *ssp, int idx) 324 __releases(ssp) 325{ 326 WARN_ON_ONCE(idx & ~0x1); 327 WARN_ON_ONCE(in_nmi()); 328 srcu_check_nmi_safety(ssp, false); 329 __srcu_read_unlock(ssp, idx); 330} 331 332/** 333 * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock 334 * 335 * Converts the preceding srcu_read_unlock into a two-way memory barrier. 336 * 337 * Call this after srcu_read_unlock, to guarantee that all memory operations 338 * that occur after smp_mb__after_srcu_read_unlock will appear to happen after 339 * the preceding srcu_read_unlock. 340 */ 341static inline void smp_mb__after_srcu_read_unlock(void) 342{ 343 /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */ 344} 345 346DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct, 347 _T->idx = srcu_read_lock(_T->lock), 348 srcu_read_unlock(_T->lock, _T->idx), 349 int idx) 350 351#endif 352