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 short srcu_idx; /* Current reader array element. */ 19 u8 srcu_gp_running; /* GP workqueue running? */ 20 u8 srcu_gp_waiting; /* GP waiting for readers? */ 21 struct swait_queue_head srcu_wq; 22 /* Last srcu_read_unlock() wakes GP. */ 23 struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ 24 struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ 25 struct work_struct srcu_work; /* For driving grace periods. */ 26 #ifdef CONFIG_DEBUG_LOCK_ALLOC 27 struct lockdep_map dep_map; 28 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 29 }; 30 31 void srcu_drive_gp(struct work_struct *wp); 32 33 #define __SRCU_STRUCT_INIT(name, __ignored) \ 34 { \ 35 .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ 36 .srcu_cb_tail = &name.srcu_cb_head, \ 37 .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ 38 __SRCU_DEP_MAP_INIT(name) \ 39 } 40 41 /* 42 * This odd _STATIC_ arrangement is needed for API compatibility with 43 * Tree SRCU, which needs some per-CPU data. 44 */ 45 #define DEFINE_SRCU(name) \ 46 struct srcu_struct name = __SRCU_STRUCT_INIT(name, name) 47 #define DEFINE_STATIC_SRCU(name) \ 48 static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name) 49 50 void synchronize_srcu(struct srcu_struct *ssp); 51 52 /* 53 * Counts the new reader in the appropriate per-CPU element of the 54 * srcu_struct. Can be invoked from irq/bh handlers, but the matching 55 * __srcu_read_unlock() must be in the same handler instance. Returns an 56 * index that must be passed to the matching srcu_read_unlock(). 57 */ 58 static inline int __srcu_read_lock(struct srcu_struct *ssp) 59 { 60 int idx; 61 62 idx = READ_ONCE(ssp->srcu_idx); 63 WRITE_ONCE(ssp->srcu_lock_nesting[idx], ssp->srcu_lock_nesting[idx] + 1); 64 return idx; 65 } 66 67 static inline void synchronize_srcu_expedited(struct srcu_struct *ssp) 68 { 69 synchronize_srcu(ssp); 70 } 71 72 static inline void srcu_barrier(struct srcu_struct *ssp) 73 { 74 synchronize_srcu(ssp); 75 } 76 77 /* Defined here to avoid size increase for non-torture kernels. */ 78 static inline void srcu_torture_stats_print(struct srcu_struct *ssp, 79 char *tt, char *tf) 80 { 81 int idx; 82 83 idx = READ_ONCE(ssp->srcu_idx) & 0x1; 84 pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n", 85 tt, tf, idx, 86 READ_ONCE(ssp->srcu_lock_nesting[!idx]), 87 READ_ONCE(ssp->srcu_lock_nesting[idx])); 88 } 89 90 #endif 91