| /* |
| * Sleepable Read-Copy Update mechanism for mutual exclusion, |
| * tiny version for non-preemptible single-CPU use. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * 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. |
| * |
| * Copyright (C) IBM Corporation, 2017 |
| * |
| * Author: Paul McKenney <paulmck@us.ibm.com> |
| */ |
| |
| #include <linux/export.h> |
| #include <linux/mutex.h> |
| #include <linux/preempt.h> |
| #include <linux/rcupdate_wait.h> |
| #include <linux/sched.h> |
| #include <linux/delay.h> |
| #include <linux/srcu.h> |
| |
| #include <linux/rcu_node_tree.h> |
| #include "rcu_segcblist.h" |
| #include "rcu.h" |
| |
| int rcu_scheduler_active __read_mostly; |
| static LIST_HEAD(srcu_boot_list); |
| static bool srcu_init_done; |
| |
| static int init_srcu_struct_fields(struct srcu_struct *sp) |
| { |
| sp->srcu_lock_nesting[0] = 0; |
| sp->srcu_lock_nesting[1] = 0; |
| init_swait_queue_head(&sp->srcu_wq); |
| sp->srcu_cb_head = NULL; |
| sp->srcu_cb_tail = &sp->srcu_cb_head; |
| sp->srcu_gp_running = false; |
| sp->srcu_gp_waiting = false; |
| sp->srcu_idx = 0; |
| INIT_WORK(&sp->srcu_work, srcu_drive_gp); |
| INIT_LIST_HEAD(&sp->srcu_work.entry); |
| return 0; |
| } |
| |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| |
| int __init_srcu_struct(struct srcu_struct *sp, const char *name, |
| struct lock_class_key *key) |
| { |
| /* Don't re-initialize a lock while it is held. */ |
| debug_check_no_locks_freed((void *)sp, sizeof(*sp)); |
| lockdep_init_map(&sp->dep_map, name, key, 0); |
| return init_srcu_struct_fields(sp); |
| } |
| EXPORT_SYMBOL_GPL(__init_srcu_struct); |
| |
| #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| |
| /* |
| * init_srcu_struct - initialize a sleep-RCU structure |
| * @sp: structure to initialize. |
| * |
| * Must invoke this on a given srcu_struct before passing that srcu_struct |
| * to any other function. Each srcu_struct represents a separate domain |
| * of SRCU protection. |
| */ |
| int init_srcu_struct(struct srcu_struct *sp) |
| { |
| return init_srcu_struct_fields(sp); |
| } |
| EXPORT_SYMBOL_GPL(init_srcu_struct); |
| |
| #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ |
| |
| /* |
| * cleanup_srcu_struct - deconstruct a sleep-RCU structure |
| * @sp: structure to clean up. |
| * |
| * Must invoke this after you are finished using a given srcu_struct that |
| * was initialized via init_srcu_struct(), else you leak memory. |
| */ |
| void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) |
| { |
| WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]); |
| if (quiesced) |
| WARN_ON(work_pending(&sp->srcu_work)); |
| else |
| flush_work(&sp->srcu_work); |
| WARN_ON(sp->srcu_gp_running); |
| WARN_ON(sp->srcu_gp_waiting); |
| WARN_ON(sp->srcu_cb_head); |
| WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail); |
| } |
| EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); |
| |
| /* |
| * Removes the count for the old reader from the appropriate element of |
| * the srcu_struct. |
| */ |
| void __srcu_read_unlock(struct srcu_struct *sp, int idx) |
| { |
| int newval = sp->srcu_lock_nesting[idx] - 1; |
| |
| WRITE_ONCE(sp->srcu_lock_nesting[idx], newval); |
| if (!newval && READ_ONCE(sp->srcu_gp_waiting)) |
| swake_up_one(&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_head *lh; |
| struct rcu_head *rhp; |
| struct srcu_struct *sp; |
| |
| sp = container_of(wp, struct srcu_struct, srcu_work); |
| if (sp->srcu_gp_running || !READ_ONCE(sp->srcu_cb_head)) |
| return; /* Already running or nothing to do. */ |
| |
| /* Remove recently arrived callbacks and wait for readers. */ |
| WRITE_ONCE(sp->srcu_gp_running, true); |
| local_irq_disable(); |
| lh = sp->srcu_cb_head; |
| sp->srcu_cb_head = NULL; |
| sp->srcu_cb_tail = &sp->srcu_cb_head; |
| local_irq_enable(); |
| 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_exclusive(sp->srcu_wq, !READ_ONCE(sp->srcu_lock_nesting[idx])); |
| WRITE_ONCE(sp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */ |
| |
| /* Invoke the callbacks we removed above. */ |
| while (lh) { |
| rhp = lh; |
| lh = lh->next; |
| local_bh_disable(); |
| rhp->func(rhp); |
| local_bh_enable(); |
| } |
| |
| /* |
| * Enable rescheduling, and if there are more callbacks, |
| * reschedule ourselves. This can race with a call_srcu() |
| * at interrupt level, but the ->srcu_gp_running checks will |
| * straighten that out. |
| */ |
| WRITE_ONCE(sp->srcu_gp_running, false); |
| if (READ_ONCE(sp->srcu_cb_head)) |
| 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 *rhp, |
| rcu_callback_t func) |
| { |
| unsigned long flags; |
| |
| rhp->func = func; |
| rhp->next = NULL; |
| local_irq_save(flags); |
| *sp->srcu_cb_tail = rhp; |
| sp->srcu_cb_tail = &rhp->next; |
| local_irq_restore(flags); |
| if (!READ_ONCE(sp->srcu_gp_running)) { |
| if (likely(srcu_init_done)) |
| schedule_work(&sp->srcu_work); |
| else if (list_empty(&sp->srcu_work.entry)) |
| list_add(&sp->srcu_work.entry, &srcu_boot_list); |
| } |
| } |
| 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); |
| |
| /* Lockdep diagnostics. */ |
| void __init rcu_scheduler_starting(void) |
| { |
| rcu_scheduler_active = RCU_SCHEDULER_RUNNING; |
| } |
| |
| /* |
| * Queue work for srcu_struct structures with early boot callbacks. |
| * The work won't actually execute until the workqueue initialization |
| * phase that takes place after the scheduler starts. |
| */ |
| void __init srcu_init(void) |
| { |
| struct srcu_struct *sp; |
| |
| srcu_init_done = true; |
| while (!list_empty(&srcu_boot_list)) { |
| sp = list_first_entry(&srcu_boot_list, |
| struct srcu_struct, srcu_work.entry); |
| list_del_init(&sp->srcu_work.entry); |
| schedule_work(&sp->srcu_work); |
| } |
| } |