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 unsigned short srcu_idx; /* Current reader array element in bit 0x2. */ 19 unsigned short srcu_idx_max; /* Furthest future srcu_idx request. */ 20 u8 srcu_gp_running; /* GP workqueue running? */ 21 u8 srcu_gp_waiting; /* GP waiting for readers? */ 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) \ 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) 48 #define DEFINE_STATIC_SRCU(name) \ 49 static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name) 50 51 void synchronize_srcu(struct srcu_struct *ssp); 52 53 /* 54 * Counts the new reader in the appropriate per-CPU element of the 55 * srcu_struct. Can be invoked from irq/bh handlers, but the matching 56 * __srcu_read_unlock() must be in the same handler instance. Returns an 57 * index that must be passed to the matching srcu_read_unlock(). 58 */ 59 static inline int __srcu_read_lock(struct srcu_struct *ssp) 60 { 61 int idx; 62 63 idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1; 64 WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1); 65 return idx; 66 } 67 68 static inline void synchronize_srcu_expedited(struct srcu_struct *ssp) 69 { 70 synchronize_srcu(ssp); 71 } 72 73 static inline void srcu_barrier(struct srcu_struct *ssp) 74 { 75 synchronize_srcu(ssp); 76 } 77 78 /* Defined here to avoid size increase for non-torture kernels. */ 79 static inline void srcu_torture_stats_print(struct srcu_struct *ssp, 80 char *tt, char *tf) 81 { 82 int idx; 83 84 idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1; 85 pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n", 86 tt, tf, idx, 87 data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])), 88 data_race(READ_ONCE(ssp->srcu_lock_nesting[idx]))); 89 } 90 91 #endif 92