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e260be673a
This patch implements a new version of RCU which allows its read-side critical sections to be preempted. It uses a set of counter pairs to keep track of the read-side critical sections and flips them when all tasks exit read-side critical section. The details of this implementation can be found in this paper - http://www.rdrop.com/users/paulmck/RCU/OLSrtRCU.2006.08.11a.pdf and the article- http://lwn.net/Articles/253651/ This patch was developed as a part of the -rt kernel development and meant to provide better latencies when read-side critical sections of RCU don't disable preemption. As a consequence of keeping track of RCU readers, the readers have a slight overhead (optimizations in the paper). This implementation co-exists with the "classic" RCU implementations and can be switched to at compiler. Also includes RCU tracing summarized in debugfs. [ akpm@linux-foundation.org: build fixes on non-preempt architectures ] Signed-off-by: Gautham R Shenoy <ego@in.ibm.com> Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com> Signed-off-by: Paul E. McKenney <paulmck@us.ibm.com> Reviewed-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion (RT implementation)
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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, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright (C) IBM Corporation, 2006
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*
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* Author: Paul McKenney <paulmck@us.ibm.com>
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*
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* Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
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* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
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* Papers:
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* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
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* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
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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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*/
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#ifndef __LINUX_RCUPREEMPT_H
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#define __LINUX_RCUPREEMPT_H
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#ifdef __KERNEL__
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#include <linux/cache.h>
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#include <linux/spinlock.h>
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#include <linux/threads.h>
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#include <linux/percpu.h>
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#include <linux/cpumask.h>
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#include <linux/seqlock.h>
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#define rcu_qsctr_inc(cpu)
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#define rcu_bh_qsctr_inc(cpu)
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#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
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extern void __rcu_read_lock(void);
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extern void __rcu_read_unlock(void);
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extern int rcu_pending(int cpu);
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extern int rcu_needs_cpu(int cpu);
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#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
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#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
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extern void __synchronize_sched(void);
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extern void __rcu_init(void);
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extern void rcu_check_callbacks(int cpu, int user);
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extern void rcu_restart_cpu(int cpu);
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extern long rcu_batches_completed(void);
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/*
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* Return the number of RCU batches processed thus far. Useful for debug
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* and statistic. The _bh variant is identifcal to straight RCU
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*/
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static inline long rcu_batches_completed_bh(void)
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{
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return rcu_batches_completed();
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}
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#ifdef CONFIG_RCU_TRACE
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struct rcupreempt_trace;
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extern long *rcupreempt_flipctr(int cpu);
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extern long rcupreempt_data_completed(void);
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extern int rcupreempt_flip_flag(int cpu);
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extern int rcupreempt_mb_flag(int cpu);
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extern char *rcupreempt_try_flip_state_name(void);
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extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
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#endif
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struct softirq_action;
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#endif /* __KERNEL__ */
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#endif /* __LINUX_RCUPREEMPT_H */
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