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194 lines
7.7 KiB
C
194 lines
7.7 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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* tree variant.
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*
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* Copyright (C) IBM Corporation, 2017
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*
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* Author: Paul McKenney <paulmck@linux.ibm.com>
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*/
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#ifndef _LINUX_SRCU_TREE_H
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#define _LINUX_SRCU_TREE_H
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#include <linux/rcu_node_tree.h>
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#include <linux/completion.h>
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struct srcu_node;
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struct srcu_struct;
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/*
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* Per-CPU structure feeding into leaf srcu_node, similar in function
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* to rcu_node.
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*/
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struct srcu_data {
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/* Read-side state. */
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atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */
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atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */
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int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */
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/* Update-side state. */
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spinlock_t __private lock ____cacheline_internodealigned_in_smp;
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struct rcu_segcblist srcu_cblist; /* List of callbacks.*/
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unsigned long srcu_gp_seq_needed; /* Furthest future GP needed. */
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unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
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bool srcu_cblist_invoking; /* Invoking these CBs? */
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struct timer_list delay_work; /* Delay for CB invoking */
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struct work_struct work; /* Context for CB invoking. */
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struct rcu_head srcu_barrier_head; /* For srcu_barrier() use. */
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struct srcu_node *mynode; /* Leaf srcu_node. */
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unsigned long grpmask; /* Mask for leaf srcu_node */
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/* ->srcu_data_have_cbs[]. */
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int cpu;
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struct srcu_struct *ssp;
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};
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/*
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* Node in SRCU combining tree, similar in function to rcu_data.
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*/
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struct srcu_node {
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spinlock_t __private lock;
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unsigned long srcu_have_cbs[4]; /* GP seq for children having CBs, but only */
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/* if greater than ->srcu_gp_seq. */
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unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs have CBs for given GP? */
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unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
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struct srcu_node *srcu_parent; /* Next up in tree. */
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int grplo; /* Least CPU for node. */
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int grphi; /* Biggest CPU for node. */
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};
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/*
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* Per-SRCU-domain structure, update-side data linked from srcu_struct.
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*/
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struct srcu_usage {
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struct srcu_node *node; /* Combining tree. */
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struct srcu_node *level[RCU_NUM_LVLS + 1];
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/* First node at each level. */
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int srcu_size_state; /* Small-to-big transition state. */
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struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
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spinlock_t __private lock; /* Protect counters and size state. */
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struct mutex srcu_gp_mutex; /* Serialize GP work. */
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unsigned long srcu_gp_seq; /* Grace-period seq #. */
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unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */
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unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
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unsigned long srcu_gp_start; /* Last GP start timestamp (jiffies) */
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unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */
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unsigned long srcu_size_jiffies; /* Current contention-measurement interval. */
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unsigned long srcu_n_lock_retries; /* Contention events in current interval. */
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unsigned long srcu_n_exp_nodelay; /* # expedited no-delays in current GP phase. */
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bool sda_is_static; /* May ->sda be passed to free_percpu()? */
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unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
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struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */
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struct completion srcu_barrier_completion;
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/* Awaken barrier rq at end. */
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atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */
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/* callback for the barrier */
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/* operation. */
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unsigned long reschedule_jiffies;
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unsigned long reschedule_count;
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struct delayed_work work;
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struct srcu_struct *srcu_ssp;
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};
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/*
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* Per-SRCU-domain structure, similar in function to rcu_state.
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*/
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struct srcu_struct {
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unsigned int srcu_idx; /* Current rdr array element. */
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struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
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struct lockdep_map dep_map;
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struct srcu_usage *srcu_sup; /* Update-side data. */
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};
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// Values for size state variable (->srcu_size_state). Once the state
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// has been set to SRCU_SIZE_ALLOC, the grace-period code advances through
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// this state machine one step per grace period until the SRCU_SIZE_BIG state
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// is reached. Otherwise, the state machine remains in the SRCU_SIZE_SMALL
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// state indefinitely.
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#define SRCU_SIZE_SMALL 0 // No srcu_node combining tree, ->node == NULL
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#define SRCU_SIZE_ALLOC 1 // An srcu_node tree is being allocated, initialized,
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// and then referenced by ->node. It will not be used.
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#define SRCU_SIZE_WAIT_BARRIER 2 // The srcu_node tree starts being used by everything
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// except call_srcu(), especially by srcu_barrier().
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// By the end of this state, all CPUs and threads
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// are aware of this tree's existence.
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#define SRCU_SIZE_WAIT_CALL 3 // The srcu_node tree starts being used by call_srcu().
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// By the end of this state, all of the call_srcu()
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// invocations that were running on a non-boot CPU
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// and using the boot CPU's callback queue will have
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// completed.
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#define SRCU_SIZE_WAIT_CBS1 4 // Don't trust the ->srcu_have_cbs[] grace-period
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#define SRCU_SIZE_WAIT_CBS2 5 // sequence elements or the ->srcu_data_have_cbs[]
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#define SRCU_SIZE_WAIT_CBS3 6 // CPU-bitmask elements until all four elements of
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#define SRCU_SIZE_WAIT_CBS4 7 // each array have been initialized.
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#define SRCU_SIZE_BIG 8 // The srcu_node combining tree is fully initialized
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// and all aspects of it are being put to use.
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/* Values for state variable (bottom bits of ->srcu_gp_seq). */
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#define SRCU_STATE_IDLE 0
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#define SRCU_STATE_SCAN1 1
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#define SRCU_STATE_SCAN2 2
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#define __SRCU_USAGE_INIT(name) \
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{ \
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.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
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.srcu_gp_seq_needed = -1UL, \
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.work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \
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}
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#define __SRCU_STRUCT_INIT_COMMON(name, usage_name) \
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.srcu_sup = &usage_name, \
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__SRCU_DEP_MAP_INIT(name)
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#define __SRCU_STRUCT_INIT_MODULE(name, usage_name) \
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{ \
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__SRCU_STRUCT_INIT_COMMON(name, usage_name) \
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}
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#define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name) \
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{ \
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.sda = &pcpu_name, \
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__SRCU_STRUCT_INIT_COMMON(name, usage_name) \
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}
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/*
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* Define and initialize a srcu struct at build time.
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* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
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*
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* Note that although DEFINE_STATIC_SRCU() hides the name from other
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* files, the per-CPU variable rules nevertheless require that the
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* chosen name be globally unique. These rules also prohibit use of
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* DEFINE_STATIC_SRCU() within a function. If these rules are too
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* restrictive, declare the srcu_struct manually. For example, in
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* each file:
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*
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* static struct srcu_struct my_srcu;
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*
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* Then, before the first use of each my_srcu, manually initialize it:
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*
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* init_srcu_struct(&my_srcu);
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*
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* See include/linux/percpu-defs.h for the rules on per-CPU variables.
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*/
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#ifdef MODULE
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# define __DEFINE_SRCU(name, is_static) \
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static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \
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is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage); \
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extern struct srcu_struct * const __srcu_struct_##name; \
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struct srcu_struct * const __srcu_struct_##name \
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__section("___srcu_struct_ptrs") = &name
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#else
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# define __DEFINE_SRCU(name, is_static) \
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static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \
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static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \
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is_static struct srcu_struct name = \
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__SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data)
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#endif
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#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
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#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
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void synchronize_srcu_expedited(struct srcu_struct *ssp);
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void srcu_barrier(struct srcu_struct *ssp);
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void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf);
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#endif
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