srcu: Create a tiny SRCU
In response to automated complaints about modifications to SRCU increasing its size, this commit creates a tiny SRCU that is used in SMP=n && PREEMPT=n builds. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
Родитель
dde8da6cff
Коммит
d8be81735a
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@ -34,28 +34,7 @@
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#include <linux/workqueue.h>
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#include <linux/rcu_segcblist.h>
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struct srcu_array {
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unsigned long lock_count[2];
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unsigned long unlock_count[2];
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};
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struct srcu_struct {
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unsigned long completed;
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unsigned long srcu_gp_seq;
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atomic_t srcu_exp_cnt;
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struct srcu_array __percpu *per_cpu_ref;
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spinlock_t queue_lock; /* protect ->srcu_cblist */
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struct rcu_segcblist srcu_cblist;
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struct delayed_work work;
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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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/* Values for -> state variable. */
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#define SRCU_STATE_IDLE 0
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#define SRCU_STATE_SCAN1 1
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#define SRCU_STATE_SCAN2 2
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struct srcu_struct;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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@ -77,42 +56,13 @@ int init_srcu_struct(struct srcu_struct *sp);
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#define __SRCU_DEP_MAP_INIT(srcu_name)
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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void process_srcu(struct work_struct *work);
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#define __SRCU_STRUCT_INIT(name) \
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{ \
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.completed = -300, \
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.per_cpu_ref = &name##_srcu_array, \
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.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
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.srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist),\
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.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
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__SRCU_DEP_MAP_INIT(name) \
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}
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/*
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* Define and initialize a srcu struct at build time.
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* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
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*
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* Note that although DEFINE_STATIC_SRCU() hides the name from other
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* files, the per-CPU variable rules nevertheless require that the
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* chosen name be globally unique. These rules also prohibit use of
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* DEFINE_STATIC_SRCU() within a function. If these rules are too
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* restrictive, declare the srcu_struct manually. For example, in
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* each file:
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*
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* static struct srcu_struct my_srcu;
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*
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* Then, before the first use of each my_srcu, manually initialize it:
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*
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* init_srcu_struct(&my_srcu);
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*
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* See include/linux/percpu-defs.h for the rules on per-CPU variables.
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*/
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#define __DEFINE_SRCU(name, is_static) \
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static DEFINE_PER_CPU(struct srcu_array, name##_srcu_array);\
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is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
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#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
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#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
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#ifdef CONFIG_TINY_SRCU
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#include <linux/srcutiny.h>
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#elif defined(CONFIG_TREE_SRCU)
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#include <linux/srcutree.h>
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#else
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#error "Unknown SRCU implementation specified to kernel configuration"
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#endif
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/**
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* call_srcu() - Queue a callback for invocation after an SRCU grace period
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@ -138,9 +88,6 @@ void cleanup_srcu_struct(struct srcu_struct *sp);
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int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
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void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
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void synchronize_srcu(struct srcu_struct *sp);
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void synchronize_srcu_expedited(struct srcu_struct *sp);
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unsigned long srcu_batches_completed(struct srcu_struct *sp);
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void srcu_barrier(struct srcu_struct *sp);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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@ -0,0 +1,81 @@
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/*
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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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int srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */
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struct swait_queue_head srcu_wq;
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/* Last srcu_read_unlock() wakes GP. */
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unsigned long srcu_gp_seq; /* GP seq # for callback tagging. */
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struct rcu_segcblist srcu_cblist;
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/* Pending SRCU callbacks. */
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int srcu_idx; /* Current reader array element. */
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bool srcu_gp_running; /* GP workqueue running? */
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bool srcu_gp_waiting; /* GP waiting for readers? */
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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) \
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{ \
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.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
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.srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist), \
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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)
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#define DEFINE_STATIC_SRCU(name) \
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static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
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void synchronize_srcu(struct srcu_struct *sp);
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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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static inline unsigned long srcu_batches_completed(struct srcu_struct *sp)
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{
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return 0;
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}
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#endif
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@ -0,0 +1,91 @@
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/*
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* Sleepable Read-Copy Update mechanism for mutual exclusion,
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* tree 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_TREE_H
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#define _LINUX_SRCU_TREE_H
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struct srcu_array {
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unsigned long lock_count[2];
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unsigned long unlock_count[2];
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};
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struct srcu_struct {
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unsigned long completed;
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unsigned long srcu_gp_seq;
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atomic_t srcu_exp_cnt;
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struct srcu_array __percpu *per_cpu_ref;
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spinlock_t queue_lock; /* protect ->srcu_cblist */
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struct rcu_segcblist srcu_cblist;
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struct delayed_work work;
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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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/* Values for -> state variable. */
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#define SRCU_STATE_IDLE 0
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#define SRCU_STATE_SCAN1 1
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#define SRCU_STATE_SCAN2 2
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void process_srcu(struct work_struct *work);
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#define __SRCU_STRUCT_INIT(name) \
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{ \
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.completed = -300, \
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.per_cpu_ref = &name##_srcu_array, \
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.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
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.srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist),\
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.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
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__SRCU_DEP_MAP_INIT(name) \
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}
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/*
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* Define and initialize a srcu struct at build time.
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* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
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*
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* Note that although DEFINE_STATIC_SRCU() hides the name from other
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* files, the per-CPU variable rules nevertheless require that the
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* chosen name be globally unique. These rules also prohibit use of
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* DEFINE_STATIC_SRCU() within a function. If these rules are too
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* restrictive, declare the srcu_struct manually. For example, in
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* each file:
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*
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* static struct srcu_struct my_srcu;
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*
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* Then, before the first use of each my_srcu, manually initialize it:
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*
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* init_srcu_struct(&my_srcu);
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*
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* See include/linux/percpu-defs.h for the rules on per-CPU variables.
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*/
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#define __DEFINE_SRCU(name, is_static) \
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static DEFINE_PER_CPU(struct srcu_array, name##_srcu_array);\
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is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
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#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
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#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
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void synchronize_srcu_expedited(struct srcu_struct *sp);
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void srcu_barrier(struct srcu_struct *sp);
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unsigned long srcu_batches_completed(struct srcu_struct *sp);
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#endif
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12
init/Kconfig
12
init/Kconfig
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@ -526,6 +526,18 @@ config SRCU
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permits arbitrary sleeping or blocking within RCU read-side critical
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sections.
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config TINY_SRCU
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bool
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default y if TINY_RCU
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help
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This option selects the single-CPU non-preemptible version of SRCU.
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config TREE_SRCU
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bool
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default y if !TINY_RCU
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help
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This option selects the full-fledged version of SRCU.
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config TASKS_RCU
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bool
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default n
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@ -3,7 +3,8 @@
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KCOV_INSTRUMENT := n
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obj-y += update.o sync.o
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obj-$(CONFIG_SRCU) += srcu.o
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obj-$(CONFIG_TREE_SRCU) += srcu.o
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obj-$(CONFIG_TINY_SRCU) += srcutiny.o
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obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
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obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
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obj-$(CONFIG_TREE_RCU) += tree.o
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@ -559,6 +559,7 @@ static void srcu_torture_barrier(void)
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static void srcu_torture_stats(void)
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{
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#ifdef CONFIG_TREE_SRCU
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int cpu;
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int idx = srcu_ctlp->completed & 0x1;
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@ -587,6 +588,7 @@ static void srcu_torture_stats(void)
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pr_cont(" %d(%ld,%ld)", cpu, c0, c1);
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}
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pr_cont("\n");
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#endif
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}
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static void srcu_torture_synchronize_expedited(void)
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@ -0,0 +1,215 @@
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/*
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* Sleepable Read-Copy Update mechanism for mutual exclusion,
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* tiny version for non-preemptible single-CPU use.
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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
|
||||
* the Free Software Foundation; either version 2 of the License, or
|
||||
* (at your option) any later version.
|
||||
*
|
||||
* This program is distributed in the hope that it will be useful,
|
||||
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
* GNU General Public License for more details.
|
||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with this program; if not, you can access it online at
|
||||
* 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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#include <linux/export.h>
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#include <linux/mutex.h>
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#include <linux/preempt.h>
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#include <linux/rcupdate_wait.h>
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#include <linux/sched.h>
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#include <linux/delay.h>
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#include <linux/srcu.h>
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#include <linux/rcu_node_tree.h>
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#include "rcu.h"
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static int init_srcu_struct_fields(struct srcu_struct *sp)
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{
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sp->srcu_lock_nesting[0] = 0;
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sp->srcu_lock_nesting[1] = 0;
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init_swait_queue_head(&sp->srcu_wq);
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sp->srcu_gp_seq = 0;
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rcu_segcblist_init(&sp->srcu_cblist);
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sp->srcu_gp_running = false;
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sp->srcu_gp_waiting = false;
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sp->srcu_idx = 0;
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INIT_WORK(&sp->srcu_work, srcu_drive_gp);
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return 0;
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}
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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int __init_srcu_struct(struct srcu_struct *sp, const char *name,
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struct lock_class_key *key)
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{
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/* Don't re-initialize a lock while it is held. */
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debug_check_no_locks_freed((void *)sp, sizeof(*sp));
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lockdep_init_map(&sp->dep_map, name, key, 0);
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return init_srcu_struct_fields(sp);
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}
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EXPORT_SYMBOL_GPL(__init_srcu_struct);
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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/*
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* init_srcu_struct - initialize a sleep-RCU structure
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* @sp: structure to initialize.
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*
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* Must invoke this on a given srcu_struct before passing that srcu_struct
|
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* to any other function. Each srcu_struct represents a separate domain
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* of SRCU protection.
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*/
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int init_srcu_struct(struct srcu_struct *sp)
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{
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return init_srcu_struct_fields(sp);
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}
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EXPORT_SYMBOL_GPL(init_srcu_struct);
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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/*
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* cleanup_srcu_struct - deconstruct a sleep-RCU structure
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* @sp: structure to clean up.
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*
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* Must invoke this after you are finished using a given srcu_struct that
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* was initialized via init_srcu_struct(), else you leak memory.
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*/
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void cleanup_srcu_struct(struct srcu_struct *sp)
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{
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WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]);
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flush_work(&sp->srcu_work);
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WARN_ON(rcu_seq_state(sp->srcu_gp_seq));
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WARN_ON(sp->srcu_gp_running);
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WARN_ON(sp->srcu_gp_waiting);
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WARN_ON(!rcu_segcblist_empty(&sp->srcu_cblist));
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}
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EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
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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. Must be called from process context.
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* Returns an index that must be passed to the matching srcu_read_unlock().
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*/
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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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EXPORT_SYMBOL_GPL(__srcu_read_lock);
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/*
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* Removes the count for the old reader from the appropriate element of
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* the srcu_struct. Must be called from process context.
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*/
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void __srcu_read_unlock(struct srcu_struct *sp, int idx)
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{
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int newval = sp->srcu_lock_nesting[idx] - 1;
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WRITE_ONCE(sp->srcu_lock_nesting[idx], newval);
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if (!newval && READ_ONCE(sp->srcu_gp_waiting))
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swake_up(&sp->srcu_wq);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
|
||||
|
||||
/*
|
||||
* Workqueue handler to drive one grace period and invoke any callbacks
|
||||
* that become ready as a result. Single-CPU and !PREEMPT operation
|
||||
* means that we get away with murder on synchronization. ;-)
|
||||
*/
|
||||
void srcu_drive_gp(struct work_struct *wp)
|
||||
{
|
||||
int idx;
|
||||
struct rcu_cblist ready_cbs;
|
||||
struct srcu_struct *sp;
|
||||
struct rcu_head *rhp;
|
||||
|
||||
sp = container_of(wp, struct srcu_struct, srcu_work);
|
||||
if (sp->srcu_gp_running || rcu_segcblist_empty(&sp->srcu_cblist))
|
||||
return; /* Already running or nothing to do. */
|
||||
|
||||
/* Tag recently arrived callbacks and wait for readers. */
|
||||
WRITE_ONCE(sp->srcu_gp_running, true);
|
||||
rcu_segcblist_accelerate(&sp->srcu_cblist,
|
||||
rcu_seq_snap(&sp->srcu_gp_seq));
|
||||
rcu_seq_start(&sp->srcu_gp_seq);
|
||||
idx = sp->srcu_idx;
|
||||
WRITE_ONCE(sp->srcu_idx, !sp->srcu_idx);
|
||||
WRITE_ONCE(sp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */
|
||||
swait_event(sp->srcu_wq, !READ_ONCE(sp->srcu_lock_nesting[idx]));
|
||||
WRITE_ONCE(sp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */
|
||||
rcu_seq_end(&sp->srcu_gp_seq);
|
||||
|
||||
/* Update callback list based on GP, and invoke ready callbacks. */
|
||||
rcu_segcblist_advance(&sp->srcu_cblist,
|
||||
rcu_seq_current(&sp->srcu_gp_seq));
|
||||
if (rcu_segcblist_ready_cbs(&sp->srcu_cblist)) {
|
||||
rcu_cblist_init(&ready_cbs);
|
||||
local_irq_disable();
|
||||
rcu_segcblist_extract_done_cbs(&sp->srcu_cblist, &ready_cbs);
|
||||
local_irq_enable();
|
||||
rhp = rcu_cblist_dequeue(&ready_cbs);
|
||||
for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) {
|
||||
local_bh_disable();
|
||||
rhp->func(rhp);
|
||||
local_bh_enable();
|
||||
}
|
||||
local_irq_disable();
|
||||
rcu_segcblist_insert_count(&sp->srcu_cblist, &ready_cbs);
|
||||
local_irq_enable();
|
||||
}
|
||||
WRITE_ONCE(sp->srcu_gp_running, false);
|
||||
|
||||
/*
|
||||
* If more callbacks, reschedule ourselves. This can race with
|
||||
* a call_srcu() at interrupt level, but the ->srcu_gp_running
|
||||
* checks will straighten that out.
|
||||
*/
|
||||
if (!rcu_segcblist_empty(&sp->srcu_cblist))
|
||||
schedule_work(&sp->srcu_work);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(srcu_drive_gp);
|
||||
|
||||
/*
|
||||
* Enqueue an SRCU callback on the specified srcu_struct structure,
|
||||
* initiating grace-period processing if it is not already running.
|
||||
*/
|
||||
void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
|
||||
rcu_callback_t func)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
head->func = func;
|
||||
local_irq_save(flags);
|
||||
rcu_segcblist_enqueue(&sp->srcu_cblist, head, false);
|
||||
local_irq_restore(flags);
|
||||
if (!READ_ONCE(sp->srcu_gp_running))
|
||||
schedule_work(&sp->srcu_work);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(call_srcu);
|
||||
|
||||
/*
|
||||
* synchronize_srcu - wait for prior SRCU read-side critical-section completion
|
||||
*/
|
||||
void synchronize_srcu(struct srcu_struct *sp)
|
||||
{
|
||||
struct rcu_synchronize rs;
|
||||
|
||||
init_rcu_head_on_stack(&rs.head);
|
||||
init_completion(&rs.completion);
|
||||
call_srcu(sp, &rs.head, wakeme_after_rcu);
|
||||
wait_for_completion(&rs.completion);
|
||||
destroy_rcu_head_on_stack(&rs.head);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(synchronize_srcu);
|
||||
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