linux - Contrib clone of linux

Age	Commit message (Expand)	Author
2019-05-21	treewide: Add SPDX license identifier - Makefile/Kconfig	Thomas Gleixner
2013-01-17	drivers/vlynq: remove depends on CONFIG_EXPERIMENTAL	Kees Cook
2010-05-14	vlynq: make whole Kconfig-menu dependant on architecture	Wolfram Sang
2009-07-06	vlynq: fix typo in Kconfig to enable debugging	Florian Fainelli
2009-06-16	drivers: add support for the TI VLYNQ bus	Florian Fainelli

/* * RCU-based infrastructure for lightweight reader-writer locking * * 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) 2015, Red Hat, Inc. * * Author: Oleg Nesterov <oleg@redhat.com> */ #include <linux/rcu_sync.h> #include <linux/sched.h> #ifdef CONFIG_PROVE_RCU #define __INIT_HELD(func) .held = func, #else #define __INIT_HELD(func) #endif static const struct { void (*sync)(void); void (*call)(struct rcu_head *, void (*)(struct rcu_head *)); void (*wait)(void); #ifdef CONFIG_PROVE_RCU int (*held)(void); #endif } gp_ops[] = { [RCU_SYNC] = { .sync = synchronize_rcu, .call = call_rcu, .wait = rcu_barrier, __INIT_HELD(rcu_read_lock_held) }, [RCU_SCHED_SYNC] = { .sync = synchronize_sched, .call = call_rcu_sched, .wait = rcu_barrier_sched, __INIT_HELD(rcu_read_lock_sched_held) }, [RCU_BH_SYNC] = { .sync = synchronize_rcu_bh, .call = call_rcu_bh, .wait = rcu_barrier_bh, __INIT_HELD(rcu_read_lock_bh_held) }, }; enum { GP_IDLE = 0, GP_PENDING, GP_PASSED }; enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY }; #define rss_lock gp_wait.lock #ifdef CONFIG_PROVE_RCU void rcu_sync_lockdep_assert(struct rcu_sync *rsp) { RCU_LOCKDEP_WARN(!gp_ops[rsp->gp_type].held(), "suspicious rcu_sync_is_idle() usage"); } EXPORT_SYMBOL_GPL(rcu_sync_lockdep_assert); #endif /** * rcu_sync_init() - Initialize an rcu_sync structure * @rsp: Pointer to rcu_sync structure to be initialized * @type: Flavor of RCU with which to synchronize rcu_sync structure */ void rcu_sync_init(struct rcu_sync *rsp, enum rcu_sync_type type) { memset(rsp, 0, sizeof(*rsp)); init_waitqueue_head(&rsp->gp_wait); rsp->gp_type = type; } /** * Must be called after rcu_sync_init() and before first use. * * Ensures rcu_sync_is_idle() returns false and rcu_sync_{enter,exit}() * pairs turn into NO-OPs. */ void rcu_sync_enter_start(struct rcu_sync *rsp) { rsp->gp_count++; rsp->gp_state = GP_PASSED; } /** * rcu_sync_enter() - Force readers onto slowpath * @rsp: Pointer to rcu_sync structure to use for synchronization * * This function is used by updaters who need readers to make use of * a slowpath during the update. After this function returns, all * subsequent calls to rcu_sync_is_idle() will return false, which * tells readers to stay off their fastpaths. A later call to * rcu_sync_exit() re-enables reader slowpaths. * * When called in isolation, rcu_sync_enter() must wait for a grace * period, however, closely spaced calls to rcu_sync_enter() can * optimize away the grace-period wait via a state machine implemented * by rcu_sync_enter(), rcu_sync_exit(), and rcu_sync_func(). */ void rcu_sync_enter(struct rcu_sync *rsp) { bool need_wait, need_sync; spin_lock_irq(&rsp->rss_lock); need_wait = rsp->gp_count++; need_sync = rsp->gp_state == GP_IDLE; if (need_sync) rsp->gp_state = GP_PENDING; spin_unlock_irq(&rsp->rss_lock); BUG_ON(need_wait && need_sync); if (need_sync) { gp_ops[rsp->gp_type].sync(); rsp->gp_state = GP_PASSED; wake_up_all(&rsp->gp_wait); } else if (need_wait) { wait_event(rsp->gp_wait, rsp->gp_state == GP_PASSED); } else { /* * Possible when there's a pending CB from a rcu_sync_exit(). * Nobody has yet been allowed the 'fast' path and thus we can * avoid doing any sync(). The callback will get 'dropped'. */ BUG_ON(rsp->gp_state != GP_PASSED); } } /** * rcu_sync_func() - Callback function managing reader access to fastpath * @rsp: Pointer to rcu_sync structure to use for synchronization * * This function is passed to one of the call_rcu() functions by * rcu_sync_exit(), so that it is invoked after a grace period following the * that invocation of rcu_sync_exit(). It takes action based on events that * have taken place in the meantime, so that closely spaced rcu_sync_enter() * and rcu_sync_exit() pairs need not wait for a grace period. * * If another rcu_sync_enter() is invoked before the grace period * ended, reset state to allow the next rcu_sync_exit() to let the * readers back onto their fastpaths (after a grace period). If both * another rcu_sync_enter() and its matching rcu_sync_exit() are invoked * before the grace period ended, re-invoke call_rcu() on behalf of that * rcu_sync_exit(). Otherwise, set all state back to idle so that readers * can again use their fastpaths. */ static void rcu_sync_func(struct rcu_head *rcu) { struct rcu_sync *rsp = container_of(rcu, struct rcu_sync, cb_head); unsigned long flags; BUG_ON(rsp->gp_state != GP_PASSED); BUG_ON(rsp->cb_state == CB_IDLE); spin_lock_irqsave(&rsp->rss_lock, flags); if (rsp->gp_count) { /* * A new rcu_sync_begin() has happened; drop the callback. */ rsp->cb_state = CB_IDLE; } else if (rsp->cb_state == CB_REPLAY) { /* * A new rcu_sync_exit() has happened; requeue the callback * to catch a later GP. */ rsp->cb_state = CB_PENDING; gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func); } else { /* * We're at least a GP after rcu_sync_exit(); eveybody will now * have observed the write side critical section. Let 'em rip!. */ rsp->cb_state = CB_IDLE; rsp->gp_state = GP_IDLE; } spin_unlock_irqrestore(&rsp->rss_lock, flags); } /** * rcu_sync_exit() - Allow readers back onto fast patch after grace period * @rsp: Pointer to rcu_sync structure to use for synchronization * * This function is used by updaters who have completed, and can therefore * now allow readers to make use of their fastpaths after a grace period * has elapsed. After this grace period has completed, all subsequent * calls to rcu_sync_is_idle() will return true, which tells readers that * they can once again use their fastpaths. */ void rcu_sync_exit(struct rcu_sync *rsp) { spin_lock_irq(&rsp->rss_lock); if (!--rsp->gp_count) { if (rsp->cb_state == CB_IDLE) { rsp->cb_state = CB_PENDING; gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func); } else if (rsp->cb_state == CB_PENDING) { rsp->cb_state = CB_REPLAY; } } spin_unlock_irq(&rsp->rss_lock); } /** * rcu_sync_dtor() - Clean up an rcu_sync structure * @rsp: Pointer to rcu_sync structure to be cleaned up */ void rcu_sync_dtor(struct rcu_sync *rsp) { int cb_state; BUG_ON(rsp->gp_count); spin_lock_irq(&rsp->rss_lock); if (rsp->cb_state == CB_REPLAY) rsp->cb_state = CB_PENDING; cb_state = rsp->cb_state; spin_unlock_irq(&rsp->rss_lock); if (cb_state != CB_IDLE) { gp_ops[rsp->gp_type].wait(); BUG_ON(rsp->cb_state != CB_IDLE); } }