104 lines
3.2 KiB
C
104 lines
3.2 KiB
C
/*
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* Sleepable Read-Copy Update mechanism for mutual exclusion,
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* tiny variant.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, you can access it online at
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* http://www.gnu.org/licenses/gpl-2.0.html.
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*
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* Copyright (C) IBM Corporation, 2017
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*
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* Author: Paul McKenney <paulmck@us.ibm.com>
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*/
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#ifndef _LINUX_SRCU_TINY_H
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#define _LINUX_SRCU_TINY_H
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#include <linux/swait.h>
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struct srcu_struct {
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short srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */
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short srcu_idx; /* Current reader array element. */
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u8 srcu_gp_running; /* GP workqueue running? */
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u8 srcu_gp_waiting; /* GP waiting for readers? */
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struct swait_queue_head srcu_wq;
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/* Last srcu_read_unlock() wakes GP. */
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struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */
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struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */
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struct work_struct srcu_work; /* For driving grace periods. */
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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};
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void srcu_drive_gp(struct work_struct *wp);
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#define __SRCU_STRUCT_INIT(name, __ignored) \
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{ \
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.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
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.srcu_cb_tail = &name.srcu_cb_head, \
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.srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \
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__SRCU_DEP_MAP_INIT(name) \
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}
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/*
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* This odd _STATIC_ arrangement is needed for API compatibility with
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* Tree SRCU, which needs some per-CPU data.
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*/
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#define DEFINE_SRCU(name) \
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struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
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#define DEFINE_STATIC_SRCU(name) \
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static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name)
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void synchronize_srcu(struct srcu_struct *sp);
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/*
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* Counts the new reader in the appropriate per-CPU element of the
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* srcu_struct. Can be invoked from irq/bh handlers, but the matching
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* __srcu_read_unlock() must be in the same handler instance. Returns an
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* index that must be passed to the matching srcu_read_unlock().
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*/
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static inline int __srcu_read_lock(struct srcu_struct *sp)
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{
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int idx;
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idx = READ_ONCE(sp->srcu_idx);
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WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1);
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return idx;
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}
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static inline void synchronize_srcu_expedited(struct srcu_struct *sp)
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{
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synchronize_srcu(sp);
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}
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static inline void srcu_barrier(struct srcu_struct *sp)
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{
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synchronize_srcu(sp);
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}
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/* Defined here to avoid size increase for non-torture kernels. */
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static inline void srcu_torture_stats_print(struct srcu_struct *sp,
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char *tt, char *tf)
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{
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int idx;
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idx = READ_ONCE(sp->srcu_idx) & 0x1;
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pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
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tt, tf, idx,
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READ_ONCE(sp->srcu_lock_nesting[!idx]),
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READ_ONCE(sp->srcu_lock_nesting[idx]));
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}
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#endif
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