317 lines
10 KiB
C
317 lines
10 KiB
C
/* SPDX-License-Identifier: GPL-2.0+ */
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/*
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* Sleepable Read-Copy Update mechanism for mutual exclusion
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*
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* Copyright (C) IBM Corporation, 2006
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* Copyright (C) Fujitsu, 2012
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*
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* Author: Paul McKenney <paulmck@linux.ibm.com>
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* Lai Jiangshan <laijs@cn.fujitsu.com>
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU/ *.txt
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*
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*/
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#ifndef _LINUX_SRCU_H
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#define _LINUX_SRCU_H
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#include <linux/mutex.h>
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#include <linux/rcupdate.h>
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#include <linux/workqueue.h>
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#include <linux/rcu_segcblist.h>
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struct srcu_struct;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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int __init_srcu_struct(struct srcu_struct *ssp, const char *name,
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struct lock_class_key *key);
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#define init_srcu_struct(ssp) \
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({ \
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static struct lock_class_key __srcu_key; \
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\
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__init_srcu_struct((ssp), #ssp, &__srcu_key); \
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})
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#define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name },
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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int init_srcu_struct(struct srcu_struct *ssp);
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#define __SRCU_DEP_MAP_INIT(srcu_name)
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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#ifdef CONFIG_TINY_SRCU
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#include <linux/srcutiny.h>
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#elif defined(CONFIG_TREE_SRCU)
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#include <linux/srcutree.h>
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#else
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#error "Unknown SRCU implementation specified to kernel configuration"
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#endif
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void call_srcu(struct srcu_struct *ssp, struct rcu_head *head,
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void (*func)(struct rcu_head *head));
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void cleanup_srcu_struct(struct srcu_struct *ssp);
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int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp);
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void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
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void synchronize_srcu(struct srcu_struct *ssp);
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unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp);
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unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp);
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bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie);
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#ifdef CONFIG_NEED_SRCU_NMI_SAFE
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int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp);
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void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp);
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#else
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static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp)
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{
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return __srcu_read_lock(ssp);
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}
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static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
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{
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__srcu_read_unlock(ssp, idx);
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}
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#endif /* CONFIG_NEED_SRCU_NMI_SAFE */
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void srcu_init(void);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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/**
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* srcu_read_lock_held - might we be in SRCU read-side critical section?
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* @ssp: The srcu_struct structure to check
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*
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* If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU
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* read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC,
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* this assumes we are in an SRCU read-side critical section unless it can
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* prove otherwise.
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*
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* Checks debug_lockdep_rcu_enabled() to prevent false positives during boot
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* and while lockdep is disabled.
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*
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* Note that SRCU is based on its own statemachine and it doesn't
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* relies on normal RCU, it can be called from the CPU which
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* is in the idle loop from an RCU point of view or offline.
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*/
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static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
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{
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if (!debug_lockdep_rcu_enabled())
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return 1;
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return lock_is_held(&ssp->dep_map);
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}
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
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{
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return 1;
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}
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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#define SRCU_NMI_UNKNOWN 0x0
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#define SRCU_NMI_UNSAFE 0x1
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#define SRCU_NMI_SAFE 0x2
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#if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU)
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void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe);
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#else
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static inline void srcu_check_nmi_safety(struct srcu_struct *ssp,
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bool nmi_safe) { }
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#endif
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/**
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* srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing
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* @p: the pointer to fetch and protect for later dereferencing
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* @ssp: pointer to the srcu_struct, which is used to check that we
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* really are in an SRCU read-side critical section.
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* @c: condition to check for update-side use
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*
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* If PROVE_RCU is enabled, invoking this outside of an RCU read-side
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* critical section will result in an RCU-lockdep splat, unless @c evaluates
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* to 1. The @c argument will normally be a logical expression containing
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* lockdep_is_held() calls.
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*/
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#define srcu_dereference_check(p, ssp, c) \
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__rcu_dereference_check((p), __UNIQUE_ID(rcu), \
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(c) || srcu_read_lock_held(ssp), __rcu)
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/**
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* srcu_dereference - fetch SRCU-protected pointer for later dereferencing
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* @p: the pointer to fetch and protect for later dereferencing
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* @ssp: pointer to the srcu_struct, which is used to check that we
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* really are in an SRCU read-side critical section.
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*
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* Makes rcu_dereference_check() do the dirty work. If PROVE_RCU
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* is enabled, invoking this outside of an RCU read-side critical
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* section will result in an RCU-lockdep splat.
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*/
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#define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0)
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/**
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* srcu_dereference_notrace - no tracing and no lockdep calls from here
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* @p: the pointer to fetch and protect for later dereferencing
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* @ssp: pointer to the srcu_struct, which is used to check that we
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* really are in an SRCU read-side critical section.
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*/
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#define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1)
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/**
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* srcu_read_lock - register a new reader for an SRCU-protected structure.
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* @ssp: srcu_struct in which to register the new reader.
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*
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* Enter an SRCU read-side critical section. Note that SRCU read-side
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* critical sections may be nested. However, it is illegal to
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* call anything that waits on an SRCU grace period for the same
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* srcu_struct, whether directly or indirectly. Please note that
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* one way to indirectly wait on an SRCU grace period is to acquire
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* a mutex that is held elsewhere while calling synchronize_srcu() or
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* synchronize_srcu_expedited().
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*
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* Note that srcu_read_lock() and the matching srcu_read_unlock() must
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* occur in the same context, for example, it is illegal to invoke
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* srcu_read_unlock() in an irq handler if the matching srcu_read_lock()
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* was invoked in process context.
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*/
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static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
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{
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int retval;
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srcu_check_nmi_safety(ssp, false);
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retval = __srcu_read_lock(ssp);
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rcu_lock_acquire(&(ssp)->dep_map);
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return retval;
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}
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/**
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* srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure.
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* @ssp: srcu_struct in which to register the new reader.
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*
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* Enter an SRCU read-side critical section, but in an NMI-safe manner.
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* See srcu_read_lock() for more information.
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*/
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static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp)
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{
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int retval;
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srcu_check_nmi_safety(ssp, true);
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retval = __srcu_read_lock_nmisafe(ssp);
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rcu_lock_acquire(&(ssp)->dep_map);
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return retval;
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}
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/* Used by tracing, cannot be traced and cannot invoke lockdep. */
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static inline notrace int
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srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp)
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{
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int retval;
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srcu_check_nmi_safety(ssp, false);
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retval = __srcu_read_lock(ssp);
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return retval;
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}
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/**
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* srcu_down_read - register a new reader for an SRCU-protected structure.
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* @ssp: srcu_struct in which to register the new reader.
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*
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* Enter a semaphore-like SRCU read-side critical section. Note that
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* SRCU read-side critical sections may be nested. However, it is
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* illegal to call anything that waits on an SRCU grace period for the
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* same srcu_struct, whether directly or indirectly. Please note that
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* one way to indirectly wait on an SRCU grace period is to acquire
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* a mutex that is held elsewhere while calling synchronize_srcu() or
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* synchronize_srcu_expedited(). But if you want lockdep to help you
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* keep this stuff straight, you should instead use srcu_read_lock().
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*
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* The semaphore-like nature of srcu_down_read() means that the matching
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* srcu_up_read() can be invoked from some other context, for example,
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* from some other task or from an irq handler. However, neither
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* srcu_down_read() nor srcu_up_read() may be invoked from an NMI handler.
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*
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* Calls to srcu_down_read() may be nested, similar to the manner in
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* which calls to down_read() may be nested.
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*/
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static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp)
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{
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WARN_ON_ONCE(in_nmi());
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srcu_check_nmi_safety(ssp, false);
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return __srcu_read_lock(ssp);
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}
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/**
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* srcu_read_unlock - unregister a old reader from an SRCU-protected structure.
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* @ssp: srcu_struct in which to unregister the old reader.
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* @idx: return value from corresponding srcu_read_lock().
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*
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* Exit an SRCU read-side critical section.
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*/
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static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
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__releases(ssp)
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{
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WARN_ON_ONCE(idx & ~0x1);
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srcu_check_nmi_safety(ssp, false);
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rcu_lock_release(&(ssp)->dep_map);
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__srcu_read_unlock(ssp, idx);
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}
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/**
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* srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure.
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* @ssp: srcu_struct in which to unregister the old reader.
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* @idx: return value from corresponding srcu_read_lock().
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*
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* Exit an SRCU read-side critical section, but in an NMI-safe manner.
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*/
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static inline void srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx)
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__releases(ssp)
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{
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WARN_ON_ONCE(idx & ~0x1);
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srcu_check_nmi_safety(ssp, true);
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rcu_lock_release(&(ssp)->dep_map);
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__srcu_read_unlock_nmisafe(ssp, idx);
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}
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/* Used by tracing, cannot be traced and cannot call lockdep. */
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static inline notrace void
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srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp)
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{
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srcu_check_nmi_safety(ssp, false);
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__srcu_read_unlock(ssp, idx);
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}
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/**
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* srcu_up_read - unregister a old reader from an SRCU-protected structure.
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* @ssp: srcu_struct in which to unregister the old reader.
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* @idx: return value from corresponding srcu_read_lock().
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*
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* Exit an SRCU read-side critical section, but not necessarily from
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* the same context as the maching srcu_down_read().
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*/
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static inline void srcu_up_read(struct srcu_struct *ssp, int idx)
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__releases(ssp)
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{
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WARN_ON_ONCE(idx & ~0x1);
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WARN_ON_ONCE(in_nmi());
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srcu_check_nmi_safety(ssp, false);
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__srcu_read_unlock(ssp, idx);
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}
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/**
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* smp_mb__after_srcu_read_unlock - ensure full ordering after srcu_read_unlock
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*
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* Converts the preceding srcu_read_unlock into a two-way memory barrier.
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*
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* Call this after srcu_read_unlock, to guarantee that all memory operations
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* that occur after smp_mb__after_srcu_read_unlock will appear to happen after
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* the preceding srcu_read_unlock.
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*/
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static inline void smp_mb__after_srcu_read_unlock(void)
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{
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/* __srcu_read_unlock has smp_mb() internally so nothing to do here. */
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}
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#endif
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