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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
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13
include/linux/rcupdate.h
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@ -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 */