include/linux/srcu.h

1 /* SPDX-License-Identifier: GPL-2.0+ */
3  * Sleepable Read-Copy Update mechanism for mutual exclusion
11  * For detailed explanation of Read-Copy Update mechanism see -
83  * srcu_read_lock_held - might we be in SRCU read-side critical section?
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
102 	return lock_is_held(&ssp->dep_map);  in srcu_read_lock_held()
109  * srcu_lock_sync(), which is basically an empty *write*-side critical section,
113 /* Annotates a srcu_read_lock() */
119 /* Annotates a srcu_read_lock() */
125 /* Annotates a synchronize_srcu() */
157  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
160  *	really are in an SRCU read-side critical section.
161  * @c: condition to check for update-side use
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
173  * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
176  *	really are in an SRCU read-side critical section.
179  * is enabled, invoking this outside of an RCU read-side critical
180  * section will result in an RCU-lockdep splat.
185  * srcu_dereference_notrace - no tracing and no lockdep calls from here
188  *	really are in an SRCU read-side critical section.
193  * srcu_read_lock - register a new reader for an SRCU-protected structure.
196  * Enter an SRCU read-side critical section.  Note that SRCU read-side
201  * a mutex that is held elsewhere while calling synchronize_srcu() or
215 	srcu_lock_acquire(&ssp->dep_map);  in srcu_read_lock()
220  * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure.
223  * Enter an SRCU read-side critical section, but in an NMI-safe manner.
232 	rcu_try_lock_acquire(&ssp->dep_map);  in srcu_read_lock_nmisafe()
248  * srcu_down_read - register a new reader for an SRCU-protected structure.
251  * Enter a semaphore-like SRCU read-side critical section.  Note that
252  * SRCU read-side critical sections may be nested.  However, it is
256  * a mutex that is held elsewhere while calling synchronize_srcu() or
260  * The semaphore-like nature of srcu_down_read() means that the matching
276  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
280  * Exit an SRCU read-side critical section.
287 	srcu_lock_release(&ssp->dep_map);  in srcu_read_unlock()
292  * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure.
296  * Exit an SRCU read-side critical section, but in an NMI-safe manner.
303 	rcu_lock_release(&ssp->dep_map);  in srcu_read_unlock_nmisafe()
316  * srcu_up_read - unregister a old reader from an SRCU-protected structure.
320  * Exit an SRCU read-side critical section, but not necessarily from
333  * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
335  * Converts the preceding srcu_read_unlock into a two-way memory barrier.
347 		    _T->idx = srcu_read_lock(_T->lock),
348 		    srcu_read_unlock(_T->lock, _T->idx),