d28139c4e9
One necessary step towards consolidating the three flavors of RCU is to make sure that the resulting consolidated "one flavor to rule them all" correctly handles networking denial-of-service attacks. One thing that allows RCU-bh to do so is that __do_softirq() invokes rcu_bh_qs() every so often, and so something similar has to happen for consolidated RCU. This must be done carefully. For example, if a preemption-disabled region of code takes an interrupt which does softirq processing before returning, consolidated RCU must ignore the resulting rcu_bh_qs() invocations -- preemption is still disabled, and that means an RCU reader for the consolidated flavor. This commit therefore creates a new rcu_softirq_qs() that is called only from the ksoftirqd task, thus avoiding the interrupted-a-preempted-region problem. This new rcu_softirq_qs() function invokes rcu_sched_qs(), rcu_preempt_qs(), and rcu_preempt_deferred_qs(). The latter call handles any deferred quiescent states. Note that __do_softirq() still invokes rcu_bh_qs(). It will continue to do so until a later stage of cleanup when the RCU-bh flavor is removed. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Fix !SMP issue located by kbuild test robot. ]
148 lines
3.8 KiB
C
148 lines
3.8 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
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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 IBM Corporation, 2008
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*
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* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*/
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#ifndef __LINUX_TINY_H
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#define __LINUX_TINY_H
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#include <linux/ktime.h>
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struct rcu_dynticks;
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static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
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{
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return 0;
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}
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/* Never flag non-existent other CPUs! */
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static inline bool rcu_eqs_special_set(int cpu) { return false; }
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static inline unsigned long get_state_synchronize_rcu(void)
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{
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return 0;
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}
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static inline void cond_synchronize_rcu(unsigned long oldstate)
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{
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might_sleep();
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}
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static inline unsigned long get_state_synchronize_sched(void)
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{
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return 0;
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}
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static inline void cond_synchronize_sched(unsigned long oldstate)
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{
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might_sleep();
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}
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extern void rcu_barrier_bh(void);
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extern void rcu_barrier_sched(void);
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static inline void synchronize_rcu_expedited(void)
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{
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synchronize_sched(); /* Only one CPU, so pretty fast anyway!!! */
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}
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static inline void rcu_barrier(void)
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{
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rcu_barrier_sched(); /* Only one CPU, so only one list of callbacks! */
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}
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static inline void synchronize_rcu_bh(void)
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{
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synchronize_sched();
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}
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static inline void synchronize_rcu_bh_expedited(void)
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{
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synchronize_sched();
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}
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static inline void synchronize_sched_expedited(void)
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{
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synchronize_sched();
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}
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static inline void kfree_call_rcu(struct rcu_head *head,
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rcu_callback_t func)
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{
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call_rcu(head, func);
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}
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static inline void rcu_softirq_qs(void)
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{
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rcu_sched_qs();
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}
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#define rcu_note_context_switch(preempt) \
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do { \
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rcu_sched_qs(); \
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rcu_tasks_qs(current); \
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} while (0)
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static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt)
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{
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*nextevt = KTIME_MAX;
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return 0;
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}
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/*
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* Take advantage of the fact that there is only one CPU, which
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* allows us to ignore virtualization-based context switches.
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*/
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static inline void rcu_virt_note_context_switch(int cpu) { }
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static inline void rcu_cpu_stall_reset(void) { }
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static inline void rcu_idle_enter(void) { }
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static inline void rcu_idle_exit(void) { }
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static inline void rcu_irq_enter(void) { }
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static inline void rcu_irq_exit_irqson(void) { }
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static inline void rcu_irq_enter_irqson(void) { }
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static inline void rcu_irq_exit(void) { }
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static inline void exit_rcu(void) { }
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static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
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{
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return false;
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}
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static inline void rcu_preempt_deferred_qs(struct task_struct *t) { }
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#ifdef CONFIG_SRCU
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void rcu_scheduler_starting(void);
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#else /* #ifndef CONFIG_SRCU */
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static inline void rcu_scheduler_starting(void) { }
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#endif /* #else #ifndef CONFIG_SRCU */
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static inline void rcu_end_inkernel_boot(void) { }
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static inline bool rcu_is_watching(void) { return true; }
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/* Avoid RCU read-side critical sections leaking across. */
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static inline void rcu_all_qs(void) { barrier(); }
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/* RCUtree hotplug events */
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#define rcutree_prepare_cpu NULL
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#define rcutree_online_cpu NULL
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#define rcutree_offline_cpu NULL
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#define rcutree_dead_cpu NULL
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#define rcutree_dying_cpu NULL
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static inline void rcu_cpu_starting(unsigned int cpu) { }
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#endif /* __LINUX_RCUTINY_H */
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