1 /* 2 * Sleepable Read-Copy Update mechanism for mutual exclusion, 3 * tiny variant. 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, you can access it online at 17 * http://www.gnu.org/licenses/gpl-2.0.html. 18 * 19 * Copyright (C) IBM Corporation, 2017 20 * 21 * Author: Paul McKenney <[email protected]> 22 */ 23 24 #ifndef _LINUX_SRCU_TINY_H 25 #define _LINUX_SRCU_TINY_H 26 27 #include <linux/swait.h> 28 29 struct srcu_struct { 30 short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */ 31 short srcu_idx; /* Current reader array element. */ 32 u8 srcu_gp_running; /* GP workqueue running? */ 33 u8 srcu_gp_waiting; /* GP waiting for readers? */ 34 struct swait_queue_head srcu_wq; 35 /* Last srcu_read_unlock() wakes GP. */ 36 unsigned long srcu_gp_seq; /* GP seq # for callback tagging. */ 37 struct rcu_segcblist srcu_cblist; 38 /* Pending SRCU callbacks. */ 39 struct work_struct srcu_work; /* For driving grace periods. */ 40 #ifdef CONFIG_DEBUG_LOCK_ALLOC 41 struct lockdep_map dep_map; 42 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ 43 }; 44 45 void srcu_drive_gp(struct work_struct *wp); 46 47 #define __SRCU_STRUCT_INIT(name) \ 48 { \ 49 .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ 50 .srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist), \ 51 .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ 52 __SRCU_DEP_MAP_INIT(name) \ 53 } 54 55 /* 56 * This odd _STATIC_ arrangement is needed for API compatibility with 57 * Tree SRCU, which needs some per-CPU data. 58 */ 59 #define DEFINE_SRCU(name) \ 60 struct srcu_struct name = __SRCU_STRUCT_INIT(name) 61 #define DEFINE_STATIC_SRCU(name) \ 62 static struct srcu_struct name = __SRCU_STRUCT_INIT(name) 63 64 void synchronize_srcu(struct srcu_struct *sp); 65 66 /* 67 * Counts the new reader in the appropriate per-CPU element of the 68 * srcu_struct. Can be invoked from irq/bh handlers, but the matching 69 * __srcu_read_unlock() must be in the same handler instance. Returns an 70 * index that must be passed to the matching srcu_read_unlock(). 71 */ 72 static inline int __srcu_read_lock(struct srcu_struct *sp) 73 { 74 int idx; 75 76 idx = READ_ONCE(sp->srcu_idx); 77 WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1); 78 return idx; 79 } 80 81 static inline void synchronize_srcu_expedited(struct srcu_struct *sp) 82 { 83 synchronize_srcu(sp); 84 } 85 86 static inline void srcu_barrier(struct srcu_struct *sp) 87 { 88 synchronize_srcu(sp); 89 } 90 91 static inline unsigned long srcu_batches_completed(struct srcu_struct *sp) 92 { 93 return 0; 94 } 95 96 static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, 97 struct srcu_struct *sp, int *flags, 98 unsigned long *gpnum, 99 unsigned long *completed) 100 { 101 if (test_type != SRCU_FLAVOR) 102 return; 103 *flags = 0; 104 *completed = sp->srcu_gp_seq; 105 *gpnum = *completed; 106 } 107 108 #endif 109