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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>
This commit is contained in:
Paul E. McKenney
Ingo Molnar
parent
e0ecfa7917
commit
e260be673a
13 changed files with 1395 additions and 8 deletions
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@ -2130,4 +2130,3 @@ source "fs/nls/Kconfig"
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source "fs/dlm/Kconfig"
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endmenu
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@ -157,5 +157,8 @@ 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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extern long rcu_batches_completed_bh(void);
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#endif /* __KERNEL__ */
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#endif /* __LINUX_RCUCLASSIC_H */
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@ -53,7 +53,11 @@ struct rcu_head {
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void (*func)(struct rcu_head *head);
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};
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#ifdef CONFIG_CLASSIC_RCU
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#include <linux/rcuclassic.h>
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#else /* #ifdef CONFIG_CLASSIC_RCU */
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#include <linux/rcupreempt.h>
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#endif /* #else #ifdef CONFIG_CLASSIC_RCU */
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#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
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#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
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@ -231,13 +235,12 @@ extern void call_rcu_bh(struct rcu_head *head,
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/* Exported common interfaces */
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extern void synchronize_rcu(void);
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extern void rcu_barrier(void);
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/* Internal to kernel */
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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 long rcu_batches_completed(void);
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extern long rcu_batches_completed_bh(void);
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/* Internal to kernel */
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extern void rcu_init(void);
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extern int rcu_needs_cpu(int cpu);
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#endif /* __KERNEL__ */
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#endif /* __LINUX_RCUPDATE_H */
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86
include/linux/rcupreempt.h
Normal file
86
include/linux/rcupreempt.h
Normal file
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@ -0,0 +1,86 @@
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/*
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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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99
include/linux/rcupreempt_trace.h
Normal file
99
include/linux/rcupreempt_trace.h
Normal file
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@ -0,0 +1,99 @@
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/*
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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 the Preemptible Read-Copy Update mechanism see -
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* http://lwn.net/Articles/253651/
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*/
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#ifndef __LINUX_RCUPREEMPT_TRACE_H
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#define __LINUX_RCUPREEMPT_TRACE_H
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#ifdef __KERNEL__
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <asm/atomic.h>
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/*
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* PREEMPT_RCU data structures.
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*/
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struct rcupreempt_trace {
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long next_length;
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long next_add;
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long wait_length;
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long wait_add;
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long done_length;
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long done_add;
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long done_remove;
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atomic_t done_invoked;
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long rcu_check_callbacks;
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atomic_t rcu_try_flip_1;
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atomic_t rcu_try_flip_e1;
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long rcu_try_flip_i1;
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long rcu_try_flip_ie1;
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long rcu_try_flip_g1;
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long rcu_try_flip_a1;
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long rcu_try_flip_ae1;
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long rcu_try_flip_a2;
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long rcu_try_flip_z1;
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long rcu_try_flip_ze1;
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long rcu_try_flip_z2;
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long rcu_try_flip_m1;
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long rcu_try_flip_me1;
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long rcu_try_flip_m2;
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};
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#ifdef CONFIG_RCU_TRACE
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#define RCU_TRACE(fn, arg) fn(arg);
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#else
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#define RCU_TRACE(fn, arg)
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#endif
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extern void rcupreempt_trace_move2done(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_invoke(struct rcupreempt_trace *trace);
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extern void rcupreempt_trace_next_add(struct rcupreempt_trace *trace);
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#endif /* __KERNEL__ */
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#endif /* __LINUX_RCUPREEMPT_TRACE_H */
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@ -974,6 +974,11 @@ struct task_struct {
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int nr_cpus_allowed;
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unsigned int time_slice;
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#ifdef CONFIG_PREEMPT_RCU
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int rcu_read_lock_nesting;
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int rcu_flipctr_idx;
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#endif /* #ifdef CONFIG_PREEMPT_RCU */
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#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
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struct sched_info sched_info;
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#endif
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28
init/Kconfig
28
init/Kconfig
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@ -763,3 +763,31 @@ source "block/Kconfig"
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config PREEMPT_NOTIFIERS
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bool
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choice
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prompt "RCU implementation type:"
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default CLASSIC_RCU
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config CLASSIC_RCU
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bool "Classic RCU"
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help
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This option selects the classic RCU implementation that is
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designed for best read-side performance on non-realtime
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systems.
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Say Y if you are unsure.
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config PREEMPT_RCU
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bool "Preemptible RCU"
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depends on PREEMPT
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help
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This option reduces the latency of the kernel by making certain
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RCU sections preemptible. Normally RCU code is non-preemptible, if
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this option is selected then read-only RCU sections become
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preemptible. This helps latency, but may expose bugs due to
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now-naive assumptions about each RCU read-side critical section
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remaining on a given CPU through its execution.
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Say N if you are unsure.
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endchoice
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@ -63,3 +63,13 @@ config PREEMPT_BKL
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Say Y here if you are building a kernel for a desktop system.
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Say N if you are unsure.
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config RCU_TRACE
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bool "Enable tracing for RCU - currently stats in debugfs"
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select DEBUG_FS
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default y
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help
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This option provides tracing in RCU which presents stats
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in debugfs for debugging RCU implementation.
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Say Y here if you want to enable RCU tracing
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Say N if you are unsure.
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@ -6,7 +6,7 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
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exit.o itimer.o time.o softirq.o resource.o \
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sysctl.o capability.o ptrace.o timer.o user.o user_namespace.o \
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signal.o sys.o kmod.o workqueue.o pid.o \
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rcupdate.o rcuclassic.o extable.o params.o posix-timers.o \
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rcupdate.o extable.o params.o posix-timers.o \
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kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
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hrtimer.o rwsem.o latency.o nsproxy.o srcu.o \
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utsname.o notifier.o
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@ -52,6 +52,11 @@ obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
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obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
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obj-$(CONFIG_SECCOMP) += seccomp.o
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obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
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obj-$(CONFIG_CLASSIC_RCU) += rcuclassic.o
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obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o
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ifeq ($(CONFIG_PREEMPT_RCU),y)
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obj-$(CONFIG_RCU_TRACE) += rcupreempt_trace.o
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endif
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obj-$(CONFIG_RELAY) += relay.o
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obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
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obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
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@ -1045,6 +1045,10 @@ static struct task_struct *copy_process(unsigned long clone_flags,
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copy_flags(clone_flags, p);
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INIT_LIST_HEAD(&p->children);
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INIT_LIST_HEAD(&p->sibling);
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#ifdef CONFIG_PREEMPT_RCU
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p->rcu_read_lock_nesting = 0;
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p->rcu_flipctr_idx = 0;
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#endif /* #ifdef CONFIG_PREEMPT_RCU */
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p->vfork_done = NULL;
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spin_lock_init(&p->alloc_lock);
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@ -45,7 +45,6 @@
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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/* #include <linux/rcupdate.h> @@@ */
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#include <linux/cpu.h>
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#include <linux/mutex.h>
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816
kernel/rcupreempt.c
Normal file
816
kernel/rcupreempt.c
Normal file
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@ -0,0 +1,816 @@
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/*
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* Read-Copy Update mechanism for mutual exclusion, realtime 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
|
||||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
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* 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
|
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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 IBM Corporation, 2006
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*
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* Authors: Paul E. McKenney <paulmck@us.ibm.com>
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* With thanks to Esben Nielsen, Bill Huey, and Ingo Molnar
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* for pushing me away from locks and towards counters, and
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* to Suparna Bhattacharya for pushing me completely away
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* from atomic instructions on the read side.
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*
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* Papers: http://www.rdrop.com/users/paulmck/RCU
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*
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* Design Document: http://lwn.net/Articles/253651/
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU/ *.txt
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*
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/rcupdate.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <asm/atomic.h>
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#include <linux/bitops.h>
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#include <linux/module.h>
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#include <linux/completion.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/rcupdate.h>
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#include <linux/cpu.h>
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#include <linux/random.h>
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#include <linux/delay.h>
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#include <linux/byteorder/swabb.h>
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#include <linux/cpumask.h>
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#include <linux/rcupreempt_trace.h>
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/*
|
||||
* Macro that prevents the compiler from reordering accesses, but does
|
||||
* absolutely -nothing- to prevent CPUs from reordering. This is used
|
||||
* only to mediate communication between mainline code and hardware
|
||||
* interrupt and NMI handlers.
|
||||
*/
|
||||
#define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
|
||||
|
||||
/*
|
||||
* PREEMPT_RCU data structures.
|
||||
*/
|
||||
|
||||
/*
|
||||
* GP_STAGES specifies the number of times the state machine has
|
||||
* to go through the all the rcu_try_flip_states (see below)
|
||||
* in a single Grace Period.
|
||||
*
|
||||
* GP in GP_STAGES stands for Grace Period ;)
|
||||
*/
|
||||
#define GP_STAGES 2
|
||||
struct rcu_data {
|
||||
spinlock_t lock; /* Protect rcu_data fields. */
|
||||
long completed; /* Number of last completed batch. */
|
||||
int waitlistcount;
|
||||
struct tasklet_struct rcu_tasklet;
|
||||
struct rcu_head *nextlist;
|
||||
struct rcu_head **nexttail;
|
||||
struct rcu_head *waitlist[GP_STAGES];
|
||||
struct rcu_head **waittail[GP_STAGES];
|
||||
struct rcu_head *donelist;
|
||||
struct rcu_head **donetail;
|
||||
long rcu_flipctr[2];
|
||||
#ifdef CONFIG_RCU_TRACE
|
||||
struct rcupreempt_trace trace;
|
||||
#endif /* #ifdef CONFIG_RCU_TRACE */
|
||||
};
|
||||
|
||||
/*
|
||||
* States for rcu_try_flip() and friends.
|
||||
*/
|
||||
|
||||
enum rcu_try_flip_states {
|
||||
|
||||
/*
|
||||
* Stay here if nothing is happening. Flip the counter if somthing
|
||||
* starts happening. Denoted by "I"
|
||||
*/
|
||||
rcu_try_flip_idle_state,
|
||||
|
||||
/*
|
||||
* Wait here for all CPUs to notice that the counter has flipped. This
|
||||
* prevents the old set of counters from ever being incremented once
|
||||
* we leave this state, which in turn is necessary because we cannot
|
||||
* test any individual counter for zero -- we can only check the sum.
|
||||
* Denoted by "A".
|
||||
*/
|
||||
rcu_try_flip_waitack_state,
|
||||
|
||||
/*
|
||||
* Wait here for the sum of the old per-CPU counters to reach zero.
|
||||
* Denoted by "Z".
|
||||
*/
|
||||
rcu_try_flip_waitzero_state,
|
||||
|
||||
/*
|
||||
* Wait here for each of the other CPUs to execute a memory barrier.
|
||||
* This is necessary to ensure that these other CPUs really have
|
||||
* completed executing their RCU read-side critical sections, despite
|
||||
* their CPUs wildly reordering memory. Denoted by "M".
|
||||
*/
|
||||
rcu_try_flip_waitmb_state,
|
||||
};
|
||||
|
||||
struct rcu_ctrlblk {
|
||||
spinlock_t fliplock; /* Protect state-machine transitions. */
|
||||
long completed; /* Number of last completed batch. */
|
||||
enum rcu_try_flip_states rcu_try_flip_state; /* The current state of
|
||||
the rcu state machine */
|
||||
};
|
||||
|
||||
static DEFINE_PER_CPU(struct rcu_data, rcu_data);
|
||||
static struct rcu_ctrlblk rcu_ctrlblk = {
|
||||
.fliplock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.fliplock),
|
||||
.completed = 0,
|
||||
.rcu_try_flip_state = rcu_try_flip_idle_state,
|
||||
};
|
||||
|
||||
|
||||
#ifdef CONFIG_RCU_TRACE
|
||||
static char *rcu_try_flip_state_names[] =
|
||||
{ "idle", "waitack", "waitzero", "waitmb" };
|
||||
#endif /* #ifdef CONFIG_RCU_TRACE */
|
||||
|
||||
/*
|
||||
* Enum and per-CPU flag to determine when each CPU has seen
|
||||
* the most recent counter flip.
|
||||
*/
|
||||
|
||||
enum rcu_flip_flag_values {
|
||||
rcu_flip_seen, /* Steady/initial state, last flip seen. */
|
||||
/* Only GP detector can update. */
|
||||
rcu_flipped /* Flip just completed, need confirmation. */
|
||||
/* Only corresponding CPU can update. */
|
||||
};
|
||||
static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_flip_flag_values, rcu_flip_flag)
|
||||
= rcu_flip_seen;
|
||||
|
||||
/*
|
||||
* Enum and per-CPU flag to determine when each CPU has executed the
|
||||
* needed memory barrier to fence in memory references from its last RCU
|
||||
* read-side critical section in the just-completed grace period.
|
||||
*/
|
||||
|
||||
enum rcu_mb_flag_values {
|
||||
rcu_mb_done, /* Steady/initial state, no mb()s required. */
|
||||
/* Only GP detector can update. */
|
||||
rcu_mb_needed /* Flip just completed, need an mb(). */
|
||||
/* Only corresponding CPU can update. */
|
||||
};
|
||||
static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_mb_flag_values, rcu_mb_flag)
|
||||
= rcu_mb_done;
|
||||
|
||||
/*
|
||||
* RCU_DATA_ME: find the current CPU's rcu_data structure.
|
||||
* RCU_DATA_CPU: find the specified CPU's rcu_data structure.
|
||||
*/
|
||||
#define RCU_DATA_ME() (&__get_cpu_var(rcu_data))
|
||||
#define RCU_DATA_CPU(cpu) (&per_cpu(rcu_data, cpu))
|
||||
|
||||
/*
|
||||
* Helper macro for tracing when the appropriate rcu_data is not
|
||||
* cached in a local variable, but where the CPU number is so cached.
|
||||
*/
|
||||
#define RCU_TRACE_CPU(f, cpu) RCU_TRACE(f, &(RCU_DATA_CPU(cpu)->trace));
|
||||
|
||||
/*
|
||||
* Helper macro for tracing when the appropriate rcu_data is not
|
||||
* cached in a local variable.
|
||||
*/
|
||||
#define RCU_TRACE_ME(f) RCU_TRACE(f, &(RCU_DATA_ME()->trace));
|
||||
|
||||
/*
|
||||
* Helper macro for tracing when the appropriate rcu_data is pointed
|
||||
* to by a local variable.
|
||||
*/
|
||||
#define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace));
|
||||
|
||||
/*
|
||||
* Return the number of RCU batches processed thus far. Useful
|
||||
* for debug and statistics.
|
||||
*/
|
||||
long rcu_batches_completed(void)
|
||||
{
|
||||
return rcu_ctrlblk.completed;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcu_batches_completed);
|
||||
|
||||
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
|
||||
|
||||
void __rcu_read_lock(void)
|
||||
{
|
||||
int idx;
|
||||
struct task_struct *t = current;
|
||||
int nesting;
|
||||
|
||||
nesting = ACCESS_ONCE(t->rcu_read_lock_nesting);
|
||||
if (nesting != 0) {
|
||||
|
||||
/* An earlier rcu_read_lock() covers us, just count it. */
|
||||
|
||||
t->rcu_read_lock_nesting = nesting + 1;
|
||||
|
||||
} else {
|
||||
unsigned long flags;
|
||||
|
||||
/*
|
||||
* We disable interrupts for the following reasons:
|
||||
* - If we get scheduling clock interrupt here, and we
|
||||
* end up acking the counter flip, it's like a promise
|
||||
* that we will never increment the old counter again.
|
||||
* Thus we will break that promise if that
|
||||
* scheduling clock interrupt happens between the time
|
||||
* we pick the .completed field and the time that we
|
||||
* increment our counter.
|
||||
*
|
||||
* - We don't want to be preempted out here.
|
||||
*
|
||||
* NMIs can still occur, of course, and might themselves
|
||||
* contain rcu_read_lock().
|
||||
*/
|
||||
|
||||
local_irq_save(flags);
|
||||
|
||||
/*
|
||||
* Outermost nesting of rcu_read_lock(), so increment
|
||||
* the current counter for the current CPU. Use volatile
|
||||
* casts to prevent the compiler from reordering.
|
||||
*/
|
||||
|
||||
idx = ACCESS_ONCE(rcu_ctrlblk.completed) & 0x1;
|
||||
ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])++;
|
||||
|
||||
/*
|
||||
* Now that the per-CPU counter has been incremented, we
|
||||
* are protected from races with rcu_read_lock() invoked
|
||||
* from NMI handlers on this CPU. We can therefore safely
|
||||
* increment the nesting counter, relieving further NMIs
|
||||
* of the need to increment the per-CPU counter.
|
||||
*/
|
||||
|
||||
ACCESS_ONCE(t->rcu_read_lock_nesting) = nesting + 1;
|
||||
|
||||
/*
|
||||
* Now that we have preventing any NMIs from storing
|
||||
* to the ->rcu_flipctr_idx, we can safely use it to
|
||||
* remember which counter to decrement in the matching
|
||||
* rcu_read_unlock().
|
||||
*/
|
||||
|
||||
ACCESS_ONCE(t->rcu_flipctr_idx) = idx;
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__rcu_read_lock);
|
||||
|
||||
void __rcu_read_unlock(void)
|
||||
{
|
||||
int idx;
|
||||
struct task_struct *t = current;
|
||||
int nesting;
|
||||
|
||||
nesting = ACCESS_ONCE(t->rcu_read_lock_nesting);
|
||||
if (nesting > 1) {
|
||||
|
||||
/*
|
||||
* We are still protected by the enclosing rcu_read_lock(),
|
||||
* so simply decrement the counter.
|
||||
*/
|
||||
|
||||
t->rcu_read_lock_nesting = nesting - 1;
|
||||
|
||||
} else {
|
||||
unsigned long flags;
|
||||
|
||||
/*
|
||||
* Disable local interrupts to prevent the grace-period
|
||||
* detection state machine from seeing us half-done.
|
||||
* NMIs can still occur, of course, and might themselves
|
||||
* contain rcu_read_lock() and rcu_read_unlock().
|
||||
*/
|
||||
|
||||
local_irq_save(flags);
|
||||
|
||||
/*
|
||||
* Outermost nesting of rcu_read_unlock(), so we must
|
||||
* decrement the current counter for the current CPU.
|
||||
* This must be done carefully, because NMIs can
|
||||
* occur at any point in this code, and any rcu_read_lock()
|
||||
* and rcu_read_unlock() pairs in the NMI handlers
|
||||
* must interact non-destructively with this code.
|
||||
* Lots of volatile casts, and -very- careful ordering.
|
||||
*
|
||||
* Changes to this code, including this one, must be
|
||||
* inspected, validated, and tested extremely carefully!!!
|
||||
*/
|
||||
|
||||
/*
|
||||
* First, pick up the index.
|
||||
*/
|
||||
|
||||
idx = ACCESS_ONCE(t->rcu_flipctr_idx);
|
||||
|
||||
/*
|
||||
* Now that we have fetched the counter index, it is
|
||||
* safe to decrement the per-task RCU nesting counter.
|
||||
* After this, any interrupts or NMIs will increment and
|
||||
* decrement the per-CPU counters.
|
||||
*/
|
||||
ACCESS_ONCE(t->rcu_read_lock_nesting) = nesting - 1;
|
||||
|
||||
/*
|
||||
* It is now safe to decrement this task's nesting count.
|
||||
* NMIs that occur after this statement will route their
|
||||
* rcu_read_lock() calls through this "else" clause, and
|
||||
* will thus start incrementing the per-CPU counter on
|
||||
* their own. They will also clobber ->rcu_flipctr_idx,
|
||||
* but that is OK, since we have already fetched it.
|
||||
*/
|
||||
|
||||
ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])--;
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
|
||||
|
||||
/*
|
||||
* If a global counter flip has occurred since the last time that we
|
||||
* advanced callbacks, advance them. Hardware interrupts must be
|
||||
* disabled when calling this function.
|
||||
*/
|
||||
static void __rcu_advance_callbacks(struct rcu_data *rdp)
|
||||
{
|
||||
int cpu;
|
||||
int i;
|
||||
int wlc = 0;
|
||||
|
||||
if (rdp->completed != rcu_ctrlblk.completed) {
|
||||
if (rdp->waitlist[GP_STAGES - 1] != NULL) {
|
||||
*rdp->donetail = rdp->waitlist[GP_STAGES - 1];
|
||||
rdp->donetail = rdp->waittail[GP_STAGES - 1];
|
||||
RCU_TRACE_RDP(rcupreempt_trace_move2done, rdp);
|
||||
}
|
||||
for (i = GP_STAGES - 2; i >= 0; i--) {
|
||||
if (rdp->waitlist[i] != NULL) {
|
||||
rdp->waitlist[i + 1] = rdp->waitlist[i];
|
||||
rdp->waittail[i + 1] = rdp->waittail[i];
|
||||
wlc++;
|
||||
} else {
|
||||
rdp->waitlist[i + 1] = NULL;
|
||||
rdp->waittail[i + 1] =
|
||||
&rdp->waitlist[i + 1];
|
||||
}
|
||||
}
|
||||
if (rdp->nextlist != NULL) {
|
||||
rdp->waitlist[0] = rdp->nextlist;
|
||||
rdp->waittail[0] = rdp->nexttail;
|
||||
wlc++;
|
||||
rdp->nextlist = NULL;
|
||||
rdp->nexttail = &rdp->nextlist;
|
||||
RCU_TRACE_RDP(rcupreempt_trace_move2wait, rdp);
|
||||
} else {
|
||||
rdp->waitlist[0] = NULL;
|
||||
rdp->waittail[0] = &rdp->waitlist[0];
|
||||
}
|
||||
rdp->waitlistcount = wlc;
|
||||
rdp->completed = rcu_ctrlblk.completed;
|
||||
}
|
||||
|
||||
/*
|
||||
* Check to see if this CPU needs to report that it has seen
|
||||
* the most recent counter flip, thereby declaring that all
|
||||
* subsequent rcu_read_lock() invocations will respect this flip.
|
||||
*/
|
||||
|
||||
cpu = raw_smp_processor_id();
|
||||
if (per_cpu(rcu_flip_flag, cpu) == rcu_flipped) {
|
||||
smp_mb(); /* Subsequent counter accesses must see new value */
|
||||
per_cpu(rcu_flip_flag, cpu) = rcu_flip_seen;
|
||||
smp_mb(); /* Subsequent RCU read-side critical sections */
|
||||
/* seen -after- acknowledgement. */
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Get here when RCU is idle. Decide whether we need to
|
||||
* move out of idle state, and return non-zero if so.
|
||||
* "Straightforward" approach for the moment, might later
|
||||
* use callback-list lengths, grace-period duration, or
|
||||
* some such to determine when to exit idle state.
|
||||
* Might also need a pre-idle test that does not acquire
|
||||
* the lock, but let's get the simple case working first...
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_idle(void)
|
||||
{
|
||||
int cpu;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_i1);
|
||||
if (!rcu_pending(smp_processor_id())) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_ie1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Do the flip.
|
||||
*/
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_g1);
|
||||
rcu_ctrlblk.completed++; /* stands in for rcu_try_flip_g2 */
|
||||
|
||||
/*
|
||||
* Need a memory barrier so that other CPUs see the new
|
||||
* counter value before they see the subsequent change of all
|
||||
* the rcu_flip_flag instances to rcu_flipped.
|
||||
*/
|
||||
|
||||
smp_mb(); /* see above block comment. */
|
||||
|
||||
/* Now ask each CPU for acknowledgement of the flip. */
|
||||
|
||||
for_each_possible_cpu(cpu)
|
||||
per_cpu(rcu_flip_flag, cpu) = rcu_flipped;
|
||||
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for CPUs to acknowledge the flip.
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_waitack(void)
|
||||
{
|
||||
int cpu;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_a1);
|
||||
for_each_possible_cpu(cpu)
|
||||
if (per_cpu(rcu_flip_flag, cpu) != rcu_flip_seen) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_ae1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* Make sure our checks above don't bleed into subsequent
|
||||
* waiting for the sum of the counters to reach zero.
|
||||
*/
|
||||
|
||||
smp_mb(); /* see above block comment. */
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_a2);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for collective ``last'' counter to reach zero,
|
||||
* then tell all CPUs to do an end-of-grace-period memory barrier.
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_waitzero(void)
|
||||
{
|
||||
int cpu;
|
||||
int lastidx = !(rcu_ctrlblk.completed & 0x1);
|
||||
int sum = 0;
|
||||
|
||||
/* Check to see if the sum of the "last" counters is zero. */
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_z1);
|
||||
for_each_possible_cpu(cpu)
|
||||
sum += RCU_DATA_CPU(cpu)->rcu_flipctr[lastidx];
|
||||
if (sum != 0) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/*
|
||||
* This ensures that the other CPUs see the call for
|
||||
* memory barriers -after- the sum to zero has been
|
||||
* detected here
|
||||
*/
|
||||
smp_mb(); /* ^^^^^^^^^^^^ */
|
||||
|
||||
/* Call for a memory barrier from each CPU. */
|
||||
for_each_possible_cpu(cpu)
|
||||
per_cpu(rcu_mb_flag, cpu) = rcu_mb_needed;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_z2);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Wait for all CPUs to do their end-of-grace-period memory barrier.
|
||||
* Return 0 once all CPUs have done so.
|
||||
*/
|
||||
|
||||
static int
|
||||
rcu_try_flip_waitmb(void)
|
||||
{
|
||||
int cpu;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_m1);
|
||||
for_each_possible_cpu(cpu)
|
||||
if (per_cpu(rcu_mb_flag, cpu) != rcu_mb_done) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_me1);
|
||||
return 0;
|
||||
}
|
||||
|
||||
smp_mb(); /* Ensure that the above checks precede any following flip. */
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_m2);
|
||||
return 1;
|
||||
}
|
||||
|
||||
/*
|
||||
* Attempt a single flip of the counters. Remember, a single flip does
|
||||
* -not- constitute a grace period. Instead, the interval between
|
||||
* at least GP_STAGES consecutive flips is a grace period.
|
||||
*
|
||||
* If anyone is nuts enough to run this CONFIG_PREEMPT_RCU implementation
|
||||
* on a large SMP, they might want to use a hierarchical organization of
|
||||
* the per-CPU-counter pairs.
|
||||
*/
|
||||
static void rcu_try_flip(void)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_1);
|
||||
if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, flags))) {
|
||||
RCU_TRACE_ME(rcupreempt_trace_try_flip_e1);
|
||||
return;
|
||||
}
|
||||
|
||||
/*
|
||||
* Take the next transition(s) through the RCU grace-period
|
||||
* flip-counter state machine.
|
||||
*/
|
||||
|
||||
switch (rcu_ctrlblk.rcu_try_flip_state) {
|
||||
case rcu_try_flip_idle_state:
|
||||
if (rcu_try_flip_idle())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_waitack_state;
|
||||
break;
|
||||
case rcu_try_flip_waitack_state:
|
||||
if (rcu_try_flip_waitack())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_waitzero_state;
|
||||
break;
|
||||
case rcu_try_flip_waitzero_state:
|
||||
if (rcu_try_flip_waitzero())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_waitmb_state;
|
||||
break;
|
||||
case rcu_try_flip_waitmb_state:
|
||||
if (rcu_try_flip_waitmb())
|
||||
rcu_ctrlblk.rcu_try_flip_state =
|
||||
rcu_try_flip_idle_state;
|
||||
}
|
||||
spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags);
|
||||
}
|
||||
|
||||
/*
|
||||
* Check to see if this CPU needs to do a memory barrier in order to
|
||||
* ensure that any prior RCU read-side critical sections have committed
|
||||
* their counter manipulations and critical-section memory references
|
||||
* before declaring the grace period to be completed.
|
||||
*/
|
||||
static void rcu_check_mb(int cpu)
|
||||
{
|
||||
if (per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed) {
|
||||
smp_mb(); /* Ensure RCU read-side accesses are visible. */
|
||||
per_cpu(rcu_mb_flag, cpu) = rcu_mb_done;
|
||||
}
|
||||
}
|
||||
|
||||
void rcu_check_callbacks(int cpu, int user)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
rcu_check_mb(cpu);
|
||||
if (rcu_ctrlblk.completed == rdp->completed)
|
||||
rcu_try_flip();
|
||||
spin_lock_irqsave(&rdp->lock, flags);
|
||||
RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
|
||||
__rcu_advance_callbacks(rdp);
|
||||
if (rdp->donelist == NULL) {
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
} else {
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
raise_softirq(RCU_SOFTIRQ);
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Needed by dynticks, to make sure all RCU processing has finished
|
||||
* when we go idle:
|
||||
*/
|
||||
void rcu_advance_callbacks(int cpu, int user)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
if (rcu_ctrlblk.completed == rdp->completed) {
|
||||
rcu_try_flip();
|
||||
if (rcu_ctrlblk.completed == rdp->completed)
|
||||
return;
|
||||
}
|
||||
spin_lock_irqsave(&rdp->lock, flags);
|
||||
RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp);
|
||||
__rcu_advance_callbacks(rdp);
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
}
|
||||
|
||||
static void rcu_process_callbacks(struct softirq_action *unused)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_head *next, *list;
|
||||
struct rcu_data *rdp = RCU_DATA_ME();
|
||||
|
||||
spin_lock_irqsave(&rdp->lock, flags);
|
||||
list = rdp->donelist;
|
||||
if (list == NULL) {
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
return;
|
||||
}
|
||||
rdp->donelist = NULL;
|
||||
rdp->donetail = &rdp->donelist;
|
||||
RCU_TRACE_RDP(rcupreempt_trace_done_remove, rdp);
|
||||
spin_unlock_irqrestore(&rdp->lock, flags);
|
||||
while (list) {
|
||||
next = list->next;
|
||||
list->func(list);
|
||||
list = next;
|
||||
RCU_TRACE_ME(rcupreempt_trace_invoke);
|
||||
}
|
||||
}
|
||||
|
||||
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
|
||||
{
|
||||
unsigned long flags;
|
||||
struct rcu_data *rdp;
|
||||
|
||||
head->func = func;
|
||||
head->next = NULL;
|
||||
local_irq_save(flags);
|
||||
rdp = RCU_DATA_ME();
|
||||
spin_lock(&rdp->lock);
|
||||
__rcu_advance_callbacks(rdp);
|
||||
*rdp->nexttail = head;
|
||||
rdp->nexttail = &head->next;
|
||||
RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp);
|
||||
spin_unlock(&rdp->lock);
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(call_rcu);
|
||||
|
||||
/*
|
||||
* Wait until all currently running preempt_disable() code segments
|
||||
* (including hardware-irq-disable segments) complete. Note that
|
||||
* in -rt this does -not- necessarily result in all currently executing
|
||||
* interrupt -handlers- having completed.
|
||||
*/
|
||||
void __synchronize_sched(void)
|
||||
{
|
||||
cpumask_t oldmask;
|
||||
int cpu;
|
||||
|
||||
if (sched_getaffinity(0, &oldmask) < 0)
|
||||
oldmask = cpu_possible_map;
|
||||
for_each_online_cpu(cpu) {
|
||||
sched_setaffinity(0, cpumask_of_cpu(cpu));
|
||||
schedule();
|
||||
}
|
||||
sched_setaffinity(0, oldmask);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(__synchronize_sched);
|
||||
|
||||
/*
|
||||
* Check to see if any future RCU-related work will need to be done
|
||||
* by the current CPU, even if none need be done immediately, returning
|
||||
* 1 if so. Assumes that notifiers would take care of handling any
|
||||
* outstanding requests from the RCU core.
|
||||
*
|
||||
* This function is part of the RCU implementation; it is -not-
|
||||
* an exported member of the RCU API.
|
||||
*/
|
||||
int rcu_needs_cpu(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
return (rdp->donelist != NULL ||
|
||||
!!rdp->waitlistcount ||
|
||||
rdp->nextlist != NULL);
|
||||
}
|
||||
|
||||
int rcu_pending(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
/* The CPU has at least one callback queued somewhere. */
|
||||
|
||||
if (rdp->donelist != NULL ||
|
||||
!!rdp->waitlistcount ||
|
||||
rdp->nextlist != NULL)
|
||||
return 1;
|
||||
|
||||
/* The RCU core needs an acknowledgement from this CPU. */
|
||||
|
||||
if ((per_cpu(rcu_flip_flag, cpu) == rcu_flipped) ||
|
||||
(per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed))
|
||||
return 1;
|
||||
|
||||
/* This CPU has fallen behind the global grace-period number. */
|
||||
|
||||
if (rdp->completed != rcu_ctrlblk.completed)
|
||||
return 1;
|
||||
|
||||
/* Nothing needed from this CPU. */
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
void __init __rcu_init(void)
|
||||
{
|
||||
int cpu;
|
||||
int i;
|
||||
struct rcu_data *rdp;
|
||||
|
||||
printk(KERN_NOTICE "Preemptible RCU implementation.\n");
|
||||
for_each_possible_cpu(cpu) {
|
||||
rdp = RCU_DATA_CPU(cpu);
|
||||
spin_lock_init(&rdp->lock);
|
||||
rdp->completed = 0;
|
||||
rdp->waitlistcount = 0;
|
||||
rdp->nextlist = NULL;
|
||||
rdp->nexttail = &rdp->nextlist;
|
||||
for (i = 0; i < GP_STAGES; i++) {
|
||||
rdp->waitlist[i] = NULL;
|
||||
rdp->waittail[i] = &rdp->waitlist[i];
|
||||
}
|
||||
rdp->donelist = NULL;
|
||||
rdp->donetail = &rdp->donelist;
|
||||
rdp->rcu_flipctr[0] = 0;
|
||||
rdp->rcu_flipctr[1] = 0;
|
||||
}
|
||||
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
|
||||
}
|
||||
|
||||
/*
|
||||
* Deprecated, use synchronize_rcu() or synchronize_sched() instead.
|
||||
*/
|
||||
void synchronize_kernel(void)
|
||||
{
|
||||
synchronize_rcu();
|
||||
}
|
||||
|
||||
#ifdef CONFIG_RCU_TRACE
|
||||
long *rcupreempt_flipctr(int cpu)
|
||||
{
|
||||
return &RCU_DATA_CPU(cpu)->rcu_flipctr[0];
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_flipctr);
|
||||
|
||||
int rcupreempt_flip_flag(int cpu)
|
||||
{
|
||||
return per_cpu(rcu_flip_flag, cpu);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_flip_flag);
|
||||
|
||||
int rcupreempt_mb_flag(int cpu)
|
||||
{
|
||||
return per_cpu(rcu_mb_flag, cpu);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_mb_flag);
|
||||
|
||||
char *rcupreempt_try_flip_state_name(void)
|
||||
{
|
||||
return rcu_try_flip_state_names[rcu_ctrlblk.rcu_try_flip_state];
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_try_flip_state_name);
|
||||
|
||||
struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu)
|
||||
{
|
||||
struct rcu_data *rdp = RCU_DATA_CPU(cpu);
|
||||
|
||||
return &rdp->trace;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(rcupreempt_trace_cpu);
|
||||
|
||||
#endif /* #ifdef RCU_TRACE */
|
||||
330
kernel/rcupreempt_trace.c
Normal file
330
kernel/rcupreempt_trace.c
Normal file
|
|
@ -0,0 +1,330 @@
|
|||
/*
|
||||
* Read-Copy Update tracing for realtime 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 IBM Corporation, 2006
|
||||
*
|
||||
* Papers: http://www.rdrop.com/users/paulmck/RCU
|
||||
*
|
||||
* For detailed explanation of Read-Copy Update mechanism see -
|
||||
* Documentation/RCU/ *.txt
|
||||
*
|
||||
*/
|
||||
#include <linux/types.h>
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/init.h>
|
||||
#include <linux/spinlock.h>
|
||||
#include <linux/smp.h>
|
||||
#include <linux/rcupdate.h>
|
||||
#include <linux/interrupt.h>
|
||||
#include <linux/sched.h>
|
||||
#include <asm/atomic.h>
|
||||
#include <linux/bitops.h>
|
||||
#include <linux/module.h>
|
||||
#include <linux/completion.h>
|
||||
#include <linux/moduleparam.h>
|
||||
#include <linux/percpu.h>
|
||||
#include <linux/notifier.h>
|
||||
#include <linux/rcupdate.h>
|
||||
#include <linux/cpu.h>
|
||||
#include <linux/mutex.h>
|
||||
#include <linux/rcupreempt_trace.h>
|
||||
#include <linux/debugfs.h>
|
||||
|
||||
static struct mutex rcupreempt_trace_mutex;
|
||||
static char *rcupreempt_trace_buf;
|
||||
#define RCUPREEMPT_TRACE_BUF_SIZE 4096
|
||||
|
||||
void rcupreempt_trace_move2done(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->done_length += trace->wait_length;
|
||||
trace->done_add += trace->wait_length;
|
||||
trace->wait_length = 0;
|
||||
}
|
||||
void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->wait_length += trace->next_length;
|
||||
trace->wait_add += trace->next_length;
|
||||
trace->next_length = 0;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
atomic_inc(&trace->rcu_try_flip_1);
|
||||
}
|
||||
void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
atomic_inc(&trace->rcu_try_flip_e1);
|
||||
}
|
||||
void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_i1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_ie1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_g1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_a1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_ae1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_a2++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_z1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_ze1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_z2++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_m1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_me1++;
|
||||
}
|
||||
void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_try_flip_m2++;
|
||||
}
|
||||
void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->rcu_check_callbacks++;
|
||||
}
|
||||
void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->done_remove += trace->done_length;
|
||||
trace->done_length = 0;
|
||||
}
|
||||
void rcupreempt_trace_invoke(struct rcupreempt_trace *trace)
|
||||
{
|
||||
atomic_inc(&trace->done_invoked);
|
||||
}
|
||||
void rcupreempt_trace_next_add(struct rcupreempt_trace *trace)
|
||||
{
|
||||
trace->next_add++;
|
||||
trace->next_length++;
|
||||
}
|
||||
|
||||
static void rcupreempt_trace_sum(struct rcupreempt_trace *sp)
|
||||
{
|
||||
struct rcupreempt_trace *cp;
|
||||
int cpu;
|
||||
|
||||
memset(sp, 0, sizeof(*sp));
|
||||
for_each_possible_cpu(cpu) {
|
||||
cp = rcupreempt_trace_cpu(cpu);
|
||||
sp->next_length += cp->next_length;
|
||||
sp->next_add += cp->next_add;
|
||||
sp->wait_length += cp->wait_length;
|
||||
sp->wait_add += cp->wait_add;
|
||||
sp->done_length += cp->done_length;
|
||||
sp->done_add += cp->done_add;
|
||||
sp->done_remove += cp->done_remove;
|
||||
atomic_set(&sp->done_invoked, atomic_read(&cp->done_invoked));
|
||||
sp->rcu_check_callbacks += cp->rcu_check_callbacks;
|
||||
atomic_set(&sp->rcu_try_flip_1,
|
||||
atomic_read(&cp->rcu_try_flip_1));
|
||||
atomic_set(&sp->rcu_try_flip_e1,
|
||||
atomic_read(&cp->rcu_try_flip_e1));
|
||||
sp->rcu_try_flip_i1 += cp->rcu_try_flip_i1;
|
||||
sp->rcu_try_flip_ie1 += cp->rcu_try_flip_ie1;
|
||||
sp->rcu_try_flip_g1 += cp->rcu_try_flip_g1;
|
||||
sp->rcu_try_flip_a1 += cp->rcu_try_flip_a1;
|
||||
sp->rcu_try_flip_ae1 += cp->rcu_try_flip_ae1;
|
||||
sp->rcu_try_flip_a2 += cp->rcu_try_flip_a2;
|
||||
sp->rcu_try_flip_z1 += cp->rcu_try_flip_z1;
|
||||
sp->rcu_try_flip_ze1 += cp->rcu_try_flip_ze1;
|
||||
sp->rcu_try_flip_z2 += cp->rcu_try_flip_z2;
|
||||
sp->rcu_try_flip_m1 += cp->rcu_try_flip_m1;
|
||||
sp->rcu_try_flip_me1 += cp->rcu_try_flip_me1;
|
||||
sp->rcu_try_flip_m2 += cp->rcu_try_flip_m2;
|
||||
}
|
||||
}
|
||||
|
||||
static ssize_t rcustats_read(struct file *filp, char __user *buffer,
|
||||
size_t count, loff_t *ppos)
|
||||
{
|
||||
struct rcupreempt_trace trace;
|
||||
ssize_t bcount;
|
||||
int cnt = 0;
|
||||
|
||||
rcupreempt_trace_sum(&trace);
|
||||
mutex_lock(&rcupreempt_trace_mutex);
|
||||
snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt,
|
||||
"ggp=%ld rcc=%ld\n",
|
||||
rcu_batches_completed(),
|
||||
trace.rcu_check_callbacks);
|
||||
snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt,
|
||||
"na=%ld nl=%ld wa=%ld wl=%ld da=%ld dl=%ld dr=%ld di=%d\n"
|
||||
"1=%d e1=%d i1=%ld ie1=%ld g1=%ld a1=%ld ae1=%ld a2=%ld\n"
|
||||
"z1=%ld ze1=%ld z2=%ld m1=%ld me1=%ld m2=%ld\n",
|
||||
|
||||
trace.next_add, trace.next_length,
|
||||
trace.wait_add, trace.wait_length,
|
||||
trace.done_add, trace.done_length,
|
||||
trace.done_remove, atomic_read(&trace.done_invoked),
|
||||
atomic_read(&trace.rcu_try_flip_1),
|
||||
atomic_read(&trace.rcu_try_flip_e1),
|
||||
trace.rcu_try_flip_i1, trace.rcu_try_flip_ie1,
|
||||
trace.rcu_try_flip_g1,
|
||||
trace.rcu_try_flip_a1, trace.rcu_try_flip_ae1,
|
||||
trace.rcu_try_flip_a2,
|
||||
trace.rcu_try_flip_z1, trace.rcu_try_flip_ze1,
|
||||
trace.rcu_try_flip_z2,
|
||||
trace.rcu_try_flip_m1, trace.rcu_try_flip_me1,
|
||||
trace.rcu_try_flip_m2);
|
||||
bcount = simple_read_from_buffer(buffer, count, ppos,
|
||||
rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
|
||||
mutex_unlock(&rcupreempt_trace_mutex);
|
||||
return bcount;
|
||||
}
|
||||
|
||||
static ssize_t rcugp_read(struct file *filp, char __user *buffer,
|
||||
size_t count, loff_t *ppos)
|
||||
{
|
||||
long oldgp = rcu_batches_completed();
|
||||
ssize_t bcount;
|
||||
|
||||
mutex_lock(&rcupreempt_trace_mutex);
|
||||
synchronize_rcu();
|
||||
snprintf(rcupreempt_trace_buf, RCUPREEMPT_TRACE_BUF_SIZE,
|
||||
"oldggp=%ld newggp=%ld\n", oldgp, rcu_batches_completed());
|
||||
bcount = simple_read_from_buffer(buffer, count, ppos,
|
||||
rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
|
||||
mutex_unlock(&rcupreempt_trace_mutex);
|
||||
return bcount;
|
||||
}
|
||||
|
||||
static ssize_t rcuctrs_read(struct file *filp, char __user *buffer,
|
||||
size_t count, loff_t *ppos)
|
||||
{
|
||||
int cnt = 0;
|
||||
int cpu;
|
||||
int f = rcu_batches_completed() & 0x1;
|
||||
ssize_t bcount;
|
||||
|
||||
mutex_lock(&rcupreempt_trace_mutex);
|
||||
|
||||
cnt += snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE,
|
||||
"CPU last cur F M\n");
|
||||
for_each_online_cpu(cpu) {
|
||||
long *flipctr = rcupreempt_flipctr(cpu);
|
||||
cnt += snprintf(&rcupreempt_trace_buf[cnt],
|
||||
RCUPREEMPT_TRACE_BUF_SIZE - cnt,
|
||||
"%3d %4ld %3ld %d %d\n",
|
||||
cpu,
|
||||
flipctr[!f],
|
||||
flipctr[f],
|
||||
rcupreempt_flip_flag(cpu),
|
||||
rcupreempt_mb_flag(cpu));
|
||||
}
|
||||
cnt += snprintf(&rcupreempt_trace_buf[cnt],
|
||||
RCUPREEMPT_TRACE_BUF_SIZE - cnt,
|
||||
"ggp = %ld, state = %s\n",
|
||||
rcu_batches_completed(),
|
||||
rcupreempt_try_flip_state_name());
|
||||
cnt += snprintf(&rcupreempt_trace_buf[cnt],
|
||||
RCUPREEMPT_TRACE_BUF_SIZE - cnt,
|
||||
"\n");
|
||||
bcount = simple_read_from_buffer(buffer, count, ppos,
|
||||
rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
|
||||
mutex_unlock(&rcupreempt_trace_mutex);
|
||||
return bcount;
|
||||
}
|
||||
|
||||
static struct file_operations rcustats_fops = {
|
||||
.owner = THIS_MODULE,
|
||||
.read = rcustats_read,
|
||||
};
|
||||
|
||||
static struct file_operations rcugp_fops = {
|
||||
.owner = THIS_MODULE,
|
||||
.read = rcugp_read,
|
||||
};
|
||||
|
||||
static struct file_operations rcuctrs_fops = {
|
||||
.owner = THIS_MODULE,
|
||||
.read = rcuctrs_read,
|
||||
};
|
||||
|
||||
static struct dentry *rcudir, *statdir, *ctrsdir, *gpdir;
|
||||
static int rcupreempt_debugfs_init(void)
|
||||
{
|
||||
rcudir = debugfs_create_dir("rcu", NULL);
|
||||
if (!rcudir)
|
||||
goto out;
|
||||
statdir = debugfs_create_file("rcustats", 0444, rcudir,
|
||||
NULL, &rcustats_fops);
|
||||
if (!statdir)
|
||||
goto free_out;
|
||||
|
||||
gpdir = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
|
||||
if (!gpdir)
|
||||
goto free_out;
|
||||
|
||||
ctrsdir = debugfs_create_file("rcuctrs", 0444, rcudir,
|
||||
NULL, &rcuctrs_fops);
|
||||
if (!ctrsdir)
|
||||
goto free_out;
|
||||
return 0;
|
||||
free_out:
|
||||
if (statdir)
|
||||
debugfs_remove(statdir);
|
||||
if (gpdir)
|
||||
debugfs_remove(gpdir);
|
||||
debugfs_remove(rcudir);
|
||||
out:
|
||||
return 1;
|
||||
}
|
||||
|
||||
static int __init rcupreempt_trace_init(void)
|
||||
{
|
||||
mutex_init(&rcupreempt_trace_mutex);
|
||||
rcupreempt_trace_buf = kmalloc(RCUPREEMPT_TRACE_BUF_SIZE, GFP_KERNEL);
|
||||
if (!rcupreempt_trace_buf)
|
||||
return 1;
|
||||
return rcupreempt_debugfs_init();
|
||||
}
|
||||
|
||||
static void __exit rcupreempt_trace_cleanup(void)
|
||||
{
|
||||
debugfs_remove(statdir);
|
||||
debugfs_remove(gpdir);
|
||||
debugfs_remove(ctrsdir);
|
||||
debugfs_remove(rcudir);
|
||||
kfree(rcupreempt_trace_buf);
|
||||
}
|
||||
|
||||
|
||||
module_init(rcupreempt_trace_init);
|
||||
module_exit(rcupreempt_trace_cleanup);
|
||||
Loading…
Reference in a new issue