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| 1 | /* SPDX-License-Identifier: GPL-2.0+ */ |
|---|---|
| 2 | /* |
| 3 | * Sleepable Read-Copy Update mechanism for mutual exclusion, |
| 4 | * tiny variant. |
| 5 | * |
| 6 | * Copyright (C) IBM Corporation, 2017 |
| 7 | * |
| 8 | * Author: Paul McKenney <paulmck@linux.ibm.com> |
| 9 | */ |
| 10 | |
| 11 | #ifndef _LINUX_SRCU_TINY_H |
| 12 | #define _LINUX_SRCU_TINY_H |
| 13 | |
| 14 | #include <linux/swait.h> |
| 15 | |
| 16 | struct srcu_struct { |
| 17 | short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */ |
| 18 | u8 srcu_gp_running; /* GP workqueue running? */ |
| 19 | u8 srcu_gp_waiting; /* GP waiting for readers? */ |
| 20 | unsigned long srcu_idx; /* Current reader array element in bit 0x2. */ |
| 21 | unsigned long srcu_idx_max; /* Furthest future srcu_idx request. */ |
| 22 | struct swait_queue_head srcu_wq; |
| 23 | /* Last srcu_read_unlock() wakes GP. */ |
| 24 | struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ |
| 25 | struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ |
| 26 | struct work_struct srcu_work; /* For driving grace periods. */ |
| 27 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| 28 | struct lockdep_map dep_map; |
| 29 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| 30 | }; |
| 31 | |
| 32 | void srcu_drive_gp(struct work_struct *wp); |
| 33 | |
| 34 | #define __SRCU_STRUCT_INIT(name, __ignored, ___ignored) \ |
| 35 | { \ |
| 36 | .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ |
| 37 | .srcu_cb_tail = &name.srcu_cb_head, \ |
| 38 | .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ |
| 39 | __SRCU_DEP_MAP_INIT(name) \ |
| 40 | } |
| 41 | |
| 42 | /* |
| 43 | * This odd _STATIC_ arrangement is needed for API compatibility with |
| 44 | * Tree SRCU, which needs some per-CPU data. |
| 45 | */ |
| 46 | #define DEFINE_SRCU(name) \ |
| 47 | struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name) |
| 48 | #define DEFINE_STATIC_SRCU(name) \ |
| 49 | static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name) |
| 50 | |
| 51 | // Dummy structure for srcu_notifier_head. |
| 52 | struct srcu_usage { }; |
| 53 | #define __SRCU_USAGE_INIT(name) { } |
| 54 | |
| 55 | void synchronize_srcu(struct srcu_struct *ssp); |
| 56 | |
| 57 | /* |
| 58 | * Counts the new reader in the appropriate per-CPU element of the |
| 59 | * srcu_struct. Can be invoked from irq/bh handlers, but the matching |
| 60 | * __srcu_read_unlock() must be in the same handler instance. Returns an |
| 61 | * index that must be passed to the matching srcu_read_unlock(). |
| 62 | */ |
| 63 | static inline int __srcu_read_lock(struct srcu_struct *ssp) |
| 64 | { |
| 65 | int idx; |
| 66 | |
| 67 | idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1; |
| 68 | WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1); |
| 69 | return idx; |
| 70 | } |
| 71 | |
| 72 | static inline void synchronize_srcu_expedited(struct srcu_struct *ssp) |
| 73 | { |
| 74 | synchronize_srcu(ssp); |
| 75 | } |
| 76 | |
| 77 | static inline void srcu_barrier(struct srcu_struct *ssp) |
| 78 | { |
| 79 | synchronize_srcu(ssp); |
| 80 | } |
| 81 | |
| 82 | /* Defined here to avoid size increase for non-torture kernels. */ |
| 83 | static inline void srcu_torture_stats_print(struct srcu_struct *ssp, |
| 84 | char *tt, char *tf) |
| 85 | { |
| 86 | int idx; |
| 87 | |
| 88 | idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1; |
| 89 | pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd) gp: %lu->%lu\n", |
| 90 | tt, tf, idx, |
| 91 | data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])), |
| 92 | data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])), |
| 93 | data_race(READ_ONCE(ssp->srcu_idx)), |
| 94 | data_race(READ_ONCE(ssp->srcu_idx_max))); |
| 95 | } |
| 96 | |
| 97 | #endif |
| 98 |
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