/* SPDX-License-Identifier: GPL-2.0+ */ /* * Sleepable Read-Copy Update mechanism for mutual exclusion, * tiny variant. * * Copyright (C) IBM Corporation, 2017 * * Author: Paul McKenney <paulmck@linux.ibm.com> */ #ifndef _LINUX_SRCU_TINY_H #define _LINUX_SRCU_TINY_H #include <linux/swait.h> struct srcu_struct { short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */ unsigned short srcu_idx; /* Current reader array element in bit 0x2. */ unsigned short srcu_idx_max; /* Furthest future srcu_idx request. */ u8 srcu_gp_running; /* GP workqueue running? */ u8 srcu_gp_waiting; /* GP waiting for readers? */ struct swait_queue_head srcu_wq; /* Last srcu_read_unlock() wakes GP. */ struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ struct work_struct srcu_work; /* For driving grace periods. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ }; void srcu_drive_gp(struct work_struct *wp); #define __SRCU_STRUCT_INIT(name, __ignored) \ { \ .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ .srcu_cb_tail = &name.srcu_cb_head, \ .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ __SRCU_DEP_MAP_INIT(name) \ } /* * This odd _STATIC_ arrangement is needed for API compatibility with * Tree SRCU, which needs some per-CPU data. */ #define DEFINE_SRCU(name) \ struct srcu_struct name = __SRCU_STRUCT_INIT(name, name) #define DEFINE_STATIC_SRCU(name) \ static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name) void synchronize_srcu(struct srcu_struct *ssp); /* * Counts the new reader in the appropriate per-CPU element of the * srcu_struct. Can be invoked from irq/bh handlers, but the matching * __srcu_read_unlock() must be in the same handler instance. Returns an * index that must be passed to the matching srcu_read_unlock(). */ static inline int __srcu_read_lock(struct srcu_struct *ssp) { int idx; idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1; WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1); return idx; } static inline void synchronize_srcu_expedited(struct srcu_struct *ssp) { synchronize_srcu(ssp); } static inline void srcu_barrier(struct srcu_struct *ssp) { synchronize_srcu(ssp); } /* Defined here to avoid size increase for non-torture kernels. */ static inline void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf) { int idx; idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1; pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n", tt, tf, idx, data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])), data_race(READ_ONCE(ssp->srcu_lock_nesting[idx]))); } #endif