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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2008-01-25 15:08:24 -0500
committerIngo Molnar <mingo@elte.hu>2008-01-25 15:08:24 -0500
commite260be673a15b6125068270e0216a3bfbfc12f87 (patch)
treef50760606d395bf6faa9e865f814761a3c88d32c /include/linux/rcupreempt.h
parente0ecfa7917cafe72f4a75f87e8bb5d8d51dc534f (diff)
Preempt-RCU: implementation
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>
Diffstat (limited to 'include/linux/rcupreempt.h')
-rw-r--r--include/linux/rcupreempt.h86
1 files changed, 86 insertions, 0 deletions
diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
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1/*
2 * Read-Copy Update mechanism for mutual exclusion (RT implementation)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright (C) IBM Corporation, 2006
19 *
20 * Author: Paul McKenney <paulmck@us.ibm.com>
21 *
22 * Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
23 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
24 * Papers:
25 * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
26 * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
27 *
28 * For detailed explanation of Read-Copy Update mechanism see -
29 * Documentation/RCU
30 *
31 */
32
33#ifndef __LINUX_RCUPREEMPT_H
34#define __LINUX_RCUPREEMPT_H
35
36#ifdef __KERNEL__
37
38#include <linux/cache.h>
39#include <linux/spinlock.h>
40#include <linux/threads.h>
41#include <linux/percpu.h>
42#include <linux/cpumask.h>
43#include <linux/seqlock.h>
44
45#define rcu_qsctr_inc(cpu)
46#define rcu_bh_qsctr_inc(cpu)
47#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
48
49extern void __rcu_read_lock(void);
50extern void __rcu_read_unlock(void);
51extern int rcu_pending(int cpu);
52extern int rcu_needs_cpu(int cpu);
53
54#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
55#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
56
57extern void __synchronize_sched(void);
58
59extern void __rcu_init(void);
60extern void rcu_check_callbacks(int cpu, int user);
61extern void rcu_restart_cpu(int cpu);
62extern long rcu_batches_completed(void);
63
64/*
65 * Return the number of RCU batches processed thus far. Useful for debug
66 * and statistic. The _bh variant is identifcal to straight RCU
67 */
68static inline long rcu_batches_completed_bh(void)
69{
70 return rcu_batches_completed();
71}
72
73#ifdef CONFIG_RCU_TRACE
74struct rcupreempt_trace;
75extern long *rcupreempt_flipctr(int cpu);
76extern long rcupreempt_data_completed(void);
77extern int rcupreempt_flip_flag(int cpu);
78extern int rcupreempt_mb_flag(int cpu);
79extern char *rcupreempt_try_flip_state_name(void);
80extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
81#endif
82
83struct softirq_action;
84
85#endif /* __KERNEL__ */
86#endif /* __LINUX_RCUPREEMPT_H */