Line data    Source code

       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             : 
      24             : struct srcu_struct;
      25             : 
      26             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      27             : 
      28             : int __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             : 
      41             : int 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             : #elif defined(CONFIG_SRCU)
      51             : #error "Unknown SRCU implementation specified to kernel configuration"
      52             : #else
      53             : /* Dummy definition for things like notifiers.  Actual use gets link error. */
      54             : struct srcu_struct { };
      55             : #endif
      56             : 
      57             : void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
      58             :                 void (*func)(struct rcu_head *head));
      59             : void cleanup_srcu_struct(struct srcu_struct *ssp);
      60             : int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
      61             : void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
      62             : void synchronize_srcu(struct srcu_struct *ssp);
      63             : unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp);
      64             : unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
      65             : bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
      66             : 
      67             : #ifdef CONFIG_SRCU
      68             : void srcu_init(void);
      69             : #else /* #ifdef CONFIG_SRCU */
      70             : static inline void srcu_init(void) { }
      71             : #endif /* #else #ifdef CONFIG_SRCU */
      72             : 
      73             : #ifdef CONFIG_DEBUG_LOCK_ALLOC
      74             : 
      75             : /**
      76             :  * srcu_read_lock_held - might we be in SRCU read-side critical section?
      77             :  * @ssp: The srcu_struct structure to check
      78             :  *
      79             :  * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
      80             :  * read-side critical section.  In absence of CONFIG_DEBUG_LOCK_ALLOC,
      81             :  * this assumes we are in an SRCU read-side critical section unless it can
      82             :  * prove otherwise.
      83             :  *
      84             :  * Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
      85             :  * and while lockdep is disabled.
      86             :  *
      87             :  * Note that SRCU is based on its own statemachine and it doesn't
      88             :  * relies on normal RCU, it can be called from the CPU which
      89             :  * is in the idle loop from an RCU point of view or offline.
      90             :  */
      91             : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
      92             : {
      93             :         if (!debug_lockdep_rcu_enabled())
      94             :                 return 1;
      95             :         return lock_is_held(&ssp->dep_map);
      96             : }
      97             : 
      98             : #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
      99             : 
     100             : static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
     101             : {
     102             :         return 1;
     103             : }
     104             : 
     105             : #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
     106             : 
     107             : /**
     108             :  * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
     109             :  * @p: the pointer to fetch and protect for later dereferencing
     110             :  * @ssp: pointer to the srcu_struct, which is used to check that we
     111             :  *      really are in an SRCU read-side critical section.
     112             :  * @c: condition to check for update-side use
     113             :  *
     114             :  * If PROVE_RCU is enabled, invoking this outside of an RCU read-side
     115             :  * critical section will result in an RCU-lockdep splat, unless @c evaluates
     116             :  * to 1.  The @c argument will normally be a logical expression containing
     117             :  * lockdep_is_held() calls.
     118             :  */
     119             : #define srcu_dereference_check(p, ssp, c) \
     120             :         __rcu_dereference_check((p), __UNIQUE_ID(rcu), \
     121             :                                 (c) || srcu_read_lock_held(ssp), __rcu)
     122             : 
     123             : /**
     124             :  * srcu_dereference - fetch SRCU-protected pointer for later dereferencing
     125             :  * @p: the pointer to fetch and protect for later dereferencing
     126             :  * @ssp: pointer to the srcu_struct, which is used to check that we
     127             :  *      really are in an SRCU read-side critical section.
     128             :  *
     129             :  * Makes rcu_dereference_check() do the dirty work.  If PROVE_RCU
     130             :  * is enabled, invoking this outside of an RCU read-side critical
     131             :  * section will result in an RCU-lockdep splat.
     132             :  */
     133             : #define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
     134             : 
     135             : /**
     136             :  * srcu_dereference_notrace - no tracing and no lockdep calls from here
     137             :  * @p: the pointer to fetch and protect for later dereferencing
     138             :  * @ssp: pointer to the srcu_struct, which is used to check that we
     139             :  *      really are in an SRCU read-side critical section.
     140             :  */
     141             : #define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
     142             : 
     143             : /**
     144             :  * srcu_read_lock - register a new reader for an SRCU-protected structure.
     145             :  * @ssp: srcu_struct in which to register the new reader.
     146             :  *
     147             :  * Enter an SRCU read-side critical section.  Note that SRCU read-side
     148             :  * critical sections may be nested.  However, it is illegal to
     149             :  * call anything that waits on an SRCU grace period for the same
     150             :  * srcu_struct, whether directly or indirectly.  Please note that
     151             :  * one way to indirectly wait on an SRCU grace period is to acquire
     152             :  * a mutex that is held elsewhere while calling synchronize_srcu() or
     153             :  * synchronize_srcu_expedited().
     154             :  *
     155             :  * Note that srcu_read_lock() and the matching srcu_read_unlock() must
     156             :  * occur in the same context, for example, it is illegal to invoke
     157             :  * srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
     158             :  * was invoked in process context.
     159             :  */
     160             : static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
     161             : {
     162             :         int retval;
     163             : 
     164           0 :         retval = __srcu_read_lock(ssp);
     165             :         rcu_lock_acquire(&(ssp)->dep_map);
     166             :         return retval;
     167             : }
     168             : 
     169             : /* Used by tracing, cannot be traced and cannot invoke lockdep. */
     170             : static inline notrace int
     171             : srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
     172             : {
     173             :         int retval;
     174             : 
     175             :         retval = __srcu_read_lock(ssp);
     176             :         return retval;
     177             : }
     178             : 
     179             : /**
     180             :  * srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
     181             :  * @ssp: srcu_struct in which to unregister the old reader.
     182             :  * @idx: return value from corresponding srcu_read_lock().
     183             :  *
     184             :  * Exit an SRCU read-side critical section.
     185             :  */
     186           0 : static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
     187             :         __releases(ssp)
     188             : {
     189           0 :         WARN_ON_ONCE(idx & ~0x1);
     190             :         rcu_lock_release(&(ssp)->dep_map);
     191           0 :         __srcu_read_unlock(ssp, idx);
     192           0 : }
     193             : 
     194             : /* Used by tracing, cannot be traced and cannot call lockdep. */
     195             : static inline notrace void
     196             : srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
     197             : {
     198             :         __srcu_read_unlock(ssp, idx);
     199             : }
     200             : 
     201             : /**
     202             :  * smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
     203             :  *
     204             :  * Converts the preceding srcu_read_unlock into a two-way memory barrier.
     205             :  *
     206             :  * Call this after srcu_read_unlock, to guarantee that all memory operations
     207             :  * that occur after smp_mb__after_srcu_read_unlock will appear to happen after
     208             :  * the preceding srcu_read_unlock.
     209             :  */
     210             : static inline void smp_mb__after_srcu_read_unlock(void)
     211             : {
     212             :         /* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
     213             : }
     214             : 
     215             : #endif