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Preempt-RCU: implementation

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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>
This commit is contained in:
Paul E. McKenney 2008-01-25 21:08:24 +01:00 • committed by Ingo Molnar
parent e0ecfa7917
commit e260be673a
13 changed files with 1395 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

3
include/linux/rcuclassic.h
View file

@ -157,5 +157,8 @@ extern void __rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
extern long rcu_batches_completed(void);
extern long rcu_batches_completed_bh(void);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUCLASSIC_H */

13
include/linux/rcupdate.h
View file

@ -53,7 +53,11 @@ struct rcu_head {
void (*func)(struct rcu_head *head);
};
#ifdef CONFIG_CLASSIC_RCU
#include <linux/rcuclassic.h>
#else /* #ifdef CONFIG_CLASSIC_RCU */
#include <linux/rcupreempt.h>
#endif /* #else #ifdef CONFIG_CLASSIC_RCU */
#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
@ -231,13 +235,12 @@ extern void call_rcu_bh(struct rcu_head *head,
/* Exported common interfaces */
extern void synchronize_rcu(void);
extern void rcu_barrier(void);
/* Internal to kernel */
extern void rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern long rcu_batches_completed(void);
extern long rcu_batches_completed_bh(void);
/* Internal to kernel */
extern void rcu_init(void);
extern int rcu_needs_cpu(int cpu);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPDATE_H */

86
include/linux/rcupreempt.h Normal file
View file

@ -0,0 +1,86 @@
/*
* Read-Copy Update mechanism for mutual exclusion (RT implementation)
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2006
*
* Author: Paul McKenney <paulmck@us.ibm.com>
*
* Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* Papers:
* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
*
* For detailed explanation of Read-Copy Update mechanism see -
* Documentation/RCU
*
*/
#ifndef __LINUX_RCUPREEMPT_H
#define __LINUX_RCUPREEMPT_H
#ifdef __KERNEL__
#include <linux/cache.h>
#include <linux/spinlock.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/cpumask.h>
#include <linux/seqlock.h>
#define rcu_qsctr_inc(cpu)
#define rcu_bh_qsctr_inc(cpu)
#define call_rcu_bh(head, rcu) call_rcu(head, rcu)
extern void __rcu_read_lock(void);
extern void __rcu_read_unlock(void);
extern int rcu_pending(int cpu);
extern int rcu_needs_cpu(int cpu);
#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); }
#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); }
extern void __synchronize_sched(void);
extern void __rcu_init(void);
extern void rcu_check_callbacks(int cpu, int user);
extern void rcu_restart_cpu(int cpu);
extern long rcu_batches_completed(void);
/*
* Return the number of RCU batches processed thus far. Useful for debug
* and statistic. The _bh variant is identifcal to straight RCU
*/
static inline long rcu_batches_completed_bh(void)
{
return rcu_batches_completed();
}
#ifdef CONFIG_RCU_TRACE
struct rcupreempt_trace;
extern long *rcupreempt_flipctr(int cpu);
extern long rcupreempt_data_completed(void);
extern int rcupreempt_flip_flag(int cpu);
extern int rcupreempt_mb_flag(int cpu);
extern char *rcupreempt_try_flip_state_name(void);
extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu);
#endif
struct softirq_action;
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPREEMPT_H */

99
include/linux/rcupreempt_trace.h Normal file
View file

@ -0,0 +1,99 @@
/*
* Read-Copy Update mechanism for mutual exclusion (RT implementation)
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2006
*
* Author: Paul McKenney <paulmck@us.ibm.com>
*
* Based on the original work by Paul McKenney <paul.mckenney@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* Papers:
* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
*
* For detailed explanation of the Preemptible Read-Copy Update mechanism see -
* http://lwn.net/Articles/253651/
*/
#ifndef __LINUX_RCUPREEMPT_TRACE_H
#define __LINUX_RCUPREEMPT_TRACE_H
#ifdef __KERNEL__
#include <linux/types.h>
#include <linux/kernel.h>
#include <asm/atomic.h>
/*
* PREEMPT_RCU data structures.
*/
struct rcupreempt_trace {
long next_length;
long next_add;
long wait_length;
long wait_add;
long done_length;
long done_add;
long done_remove;
atomic_t done_invoked;
long rcu_check_callbacks;
atomic_t rcu_try_flip_1;
atomic_t rcu_try_flip_e1;
long rcu_try_flip_i1;
long rcu_try_flip_ie1;
long rcu_try_flip_g1;
long rcu_try_flip_a1;
long rcu_try_flip_ae1;
long rcu_try_flip_a2;
long rcu_try_flip_z1;
long rcu_try_flip_ze1;
long rcu_try_flip_z2;
long rcu_try_flip_m1;
long rcu_try_flip_me1;
long rcu_try_flip_m2;
};
#ifdef CONFIG_RCU_TRACE
#define RCU_TRACE(fn, arg) fn(arg);
#else
#define RCU_TRACE(fn, arg)
#endif
extern void rcupreempt_trace_move2done(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_invoke(struct rcupreempt_trace *trace);
extern void rcupreempt_trace_next_add(struct rcupreempt_trace *trace);
#endif /* __KERNEL__ */
#endif /* __LINUX_RCUPREEMPT_TRACE_H */

5
include/linux/sched.h
View file

@ -974,6 +974,11 @@ struct task_struct {
int nr_cpus_allowed;
unsigned int time_slice;
#ifdef CONFIG_PREEMPT_RCU
int rcu_read_lock_nesting;
int rcu_flipctr_idx;
#endif /* #ifdef CONFIG_PREEMPT_RCU */
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
struct sched_info sched_info;
#endif