3.14內核代碼

rcu機制不是宣稱無鎖嗎？

但是rcu_lock_acquire那句是個鎖嗎？怎么解釋呢？求解惑

806 static inline void rcu_read_lock(void)

807 {

808 ????????__rcu_read_lock();

809 ????????__acquire(RCU);

810 ????????rcu_lock_acquire(&rcu_lock_map);

811 ????????rcu_lockdep_assert(rcu_is_watching(),

812 ???????????????????????????"rcu_read_lock() used illegally while idle");

813 }

同文件 line 313 rcu_lock_acquire 定義如下

313 #ifdef CONFIG_DEBUG_LOCK_ALLOC

314

315 static inline void rcu_lock_acquire(struct lockdep_map *map)

316 {

317 lock_acquire(map, 0, 0, 2, 1, NULL, _THIS_IP_);

318 }

lock_acquire的reference:

318 /*

319 * Acquire a lock.

320 *

321 * Values for "read":

322 *

323 * 0: exclusive (write) acquire

324 * 1: read-acquire (no recursion allowed)

325 * 2: read-acquire with same-instance recursion allowed

326 *

327 * Values for check:

328 *

329 * 0: disabled

330 * 1: simple checks (freeing, held-at-exit-time, etc.)

331 * 2: full validation

332 */

333 extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass,

334 int trylock, int read, int check,

335 struct lockdep_map *nest_lock, unsigned long ip);

336

337 extern void lock_release(struct lockdep_map *lock, int nested,

338 unsigned long ip);

總結

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