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![Paul E. McKenney](/assets/img/avatar_default.png)
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>
330 lines
9.3 KiB
C
330 lines
9.3 KiB
C
/*
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* Read-Copy Update tracing for 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
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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 IBM Corporation, 2006
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*
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* Papers: http://www.rdrop.com/users/paulmck/RCU
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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/mutex.h>
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#include <linux/rcupreempt_trace.h>
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#include <linux/debugfs.h>
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static struct mutex rcupreempt_trace_mutex;
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static char *rcupreempt_trace_buf;
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#define RCUPREEMPT_TRACE_BUF_SIZE 4096
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void rcupreempt_trace_move2done(struct rcupreempt_trace *trace)
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{
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trace->done_length += trace->wait_length;
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trace->done_add += trace->wait_length;
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trace->wait_length = 0;
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}
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void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace)
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{
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trace->wait_length += trace->next_length;
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trace->wait_add += trace->next_length;
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trace->next_length = 0;
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}
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void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace)
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{
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atomic_inc(&trace->rcu_try_flip_1);
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}
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void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace)
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{
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atomic_inc(&trace->rcu_try_flip_e1);
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}
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void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_i1++;
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}
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void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_ie1++;
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}
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void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_g1++;
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}
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void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_a1++;
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}
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void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_ae1++;
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}
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void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_a2++;
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}
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void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_z1++;
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}
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void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_ze1++;
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}
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void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_z2++;
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}
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void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_m1++;
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}
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void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_me1++;
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}
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void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace)
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{
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trace->rcu_try_flip_m2++;
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}
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void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace)
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{
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trace->rcu_check_callbacks++;
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}
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void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace)
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{
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trace->done_remove += trace->done_length;
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trace->done_length = 0;
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}
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void rcupreempt_trace_invoke(struct rcupreempt_trace *trace)
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{
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atomic_inc(&trace->done_invoked);
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}
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void rcupreempt_trace_next_add(struct rcupreempt_trace *trace)
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{
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trace->next_add++;
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trace->next_length++;
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}
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static void rcupreempt_trace_sum(struct rcupreempt_trace *sp)
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{
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struct rcupreempt_trace *cp;
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int cpu;
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memset(sp, 0, sizeof(*sp));
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for_each_possible_cpu(cpu) {
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cp = rcupreempt_trace_cpu(cpu);
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sp->next_length += cp->next_length;
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sp->next_add += cp->next_add;
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sp->wait_length += cp->wait_length;
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sp->wait_add += cp->wait_add;
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sp->done_length += cp->done_length;
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sp->done_add += cp->done_add;
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sp->done_remove += cp->done_remove;
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atomic_set(&sp->done_invoked, atomic_read(&cp->done_invoked));
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sp->rcu_check_callbacks += cp->rcu_check_callbacks;
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atomic_set(&sp->rcu_try_flip_1,
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atomic_read(&cp->rcu_try_flip_1));
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atomic_set(&sp->rcu_try_flip_e1,
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atomic_read(&cp->rcu_try_flip_e1));
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sp->rcu_try_flip_i1 += cp->rcu_try_flip_i1;
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sp->rcu_try_flip_ie1 += cp->rcu_try_flip_ie1;
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sp->rcu_try_flip_g1 += cp->rcu_try_flip_g1;
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sp->rcu_try_flip_a1 += cp->rcu_try_flip_a1;
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sp->rcu_try_flip_ae1 += cp->rcu_try_flip_ae1;
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sp->rcu_try_flip_a2 += cp->rcu_try_flip_a2;
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sp->rcu_try_flip_z1 += cp->rcu_try_flip_z1;
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sp->rcu_try_flip_ze1 += cp->rcu_try_flip_ze1;
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sp->rcu_try_flip_z2 += cp->rcu_try_flip_z2;
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sp->rcu_try_flip_m1 += cp->rcu_try_flip_m1;
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sp->rcu_try_flip_me1 += cp->rcu_try_flip_me1;
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sp->rcu_try_flip_m2 += cp->rcu_try_flip_m2;
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}
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}
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static ssize_t rcustats_read(struct file *filp, char __user *buffer,
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size_t count, loff_t *ppos)
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{
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struct rcupreempt_trace trace;
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ssize_t bcount;
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int cnt = 0;
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rcupreempt_trace_sum(&trace);
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mutex_lock(&rcupreempt_trace_mutex);
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snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt,
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"ggp=%ld rcc=%ld\n",
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rcu_batches_completed(),
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trace.rcu_check_callbacks);
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snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt,
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"na=%ld nl=%ld wa=%ld wl=%ld da=%ld dl=%ld dr=%ld di=%d\n"
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"1=%d e1=%d i1=%ld ie1=%ld g1=%ld a1=%ld ae1=%ld a2=%ld\n"
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"z1=%ld ze1=%ld z2=%ld m1=%ld me1=%ld m2=%ld\n",
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trace.next_add, trace.next_length,
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trace.wait_add, trace.wait_length,
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trace.done_add, trace.done_length,
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trace.done_remove, atomic_read(&trace.done_invoked),
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atomic_read(&trace.rcu_try_flip_1),
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atomic_read(&trace.rcu_try_flip_e1),
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trace.rcu_try_flip_i1, trace.rcu_try_flip_ie1,
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trace.rcu_try_flip_g1,
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trace.rcu_try_flip_a1, trace.rcu_try_flip_ae1,
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trace.rcu_try_flip_a2,
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trace.rcu_try_flip_z1, trace.rcu_try_flip_ze1,
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trace.rcu_try_flip_z2,
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trace.rcu_try_flip_m1, trace.rcu_try_flip_me1,
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trace.rcu_try_flip_m2);
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bcount = simple_read_from_buffer(buffer, count, ppos,
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rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
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mutex_unlock(&rcupreempt_trace_mutex);
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return bcount;
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}
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static ssize_t rcugp_read(struct file *filp, char __user *buffer,
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size_t count, loff_t *ppos)
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{
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long oldgp = rcu_batches_completed();
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ssize_t bcount;
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mutex_lock(&rcupreempt_trace_mutex);
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synchronize_rcu();
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snprintf(rcupreempt_trace_buf, RCUPREEMPT_TRACE_BUF_SIZE,
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"oldggp=%ld newggp=%ld\n", oldgp, rcu_batches_completed());
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bcount = simple_read_from_buffer(buffer, count, ppos,
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rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
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mutex_unlock(&rcupreempt_trace_mutex);
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return bcount;
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}
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static ssize_t rcuctrs_read(struct file *filp, char __user *buffer,
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size_t count, loff_t *ppos)
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{
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int cnt = 0;
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int cpu;
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int f = rcu_batches_completed() & 0x1;
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ssize_t bcount;
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mutex_lock(&rcupreempt_trace_mutex);
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cnt += snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE,
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"CPU last cur F M\n");
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for_each_online_cpu(cpu) {
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long *flipctr = rcupreempt_flipctr(cpu);
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cnt += snprintf(&rcupreempt_trace_buf[cnt],
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RCUPREEMPT_TRACE_BUF_SIZE - cnt,
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"%3d %4ld %3ld %d %d\n",
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cpu,
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flipctr[!f],
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flipctr[f],
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rcupreempt_flip_flag(cpu),
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rcupreempt_mb_flag(cpu));
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}
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cnt += snprintf(&rcupreempt_trace_buf[cnt],
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RCUPREEMPT_TRACE_BUF_SIZE - cnt,
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"ggp = %ld, state = %s\n",
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rcu_batches_completed(),
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rcupreempt_try_flip_state_name());
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cnt += snprintf(&rcupreempt_trace_buf[cnt],
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RCUPREEMPT_TRACE_BUF_SIZE - cnt,
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"\n");
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bcount = simple_read_from_buffer(buffer, count, ppos,
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rcupreempt_trace_buf, strlen(rcupreempt_trace_buf));
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mutex_unlock(&rcupreempt_trace_mutex);
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return bcount;
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}
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static struct file_operations rcustats_fops = {
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.owner = THIS_MODULE,
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.read = rcustats_read,
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};
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static struct file_operations rcugp_fops = {
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.owner = THIS_MODULE,
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.read = rcugp_read,
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};
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static struct file_operations rcuctrs_fops = {
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.owner = THIS_MODULE,
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.read = rcuctrs_read,
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};
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static struct dentry *rcudir, *statdir, *ctrsdir, *gpdir;
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static int rcupreempt_debugfs_init(void)
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{
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rcudir = debugfs_create_dir("rcu", NULL);
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if (!rcudir)
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goto out;
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statdir = debugfs_create_file("rcustats", 0444, rcudir,
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NULL, &rcustats_fops);
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if (!statdir)
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goto free_out;
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gpdir = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
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if (!gpdir)
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goto free_out;
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ctrsdir = debugfs_create_file("rcuctrs", 0444, rcudir,
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NULL, &rcuctrs_fops);
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if (!ctrsdir)
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goto free_out;
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return 0;
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free_out:
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if (statdir)
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debugfs_remove(statdir);
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if (gpdir)
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debugfs_remove(gpdir);
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debugfs_remove(rcudir);
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out:
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return 1;
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}
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static int __init rcupreempt_trace_init(void)
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{
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mutex_init(&rcupreempt_trace_mutex);
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rcupreempt_trace_buf = kmalloc(RCUPREEMPT_TRACE_BUF_SIZE, GFP_KERNEL);
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if (!rcupreempt_trace_buf)
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return 1;
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return rcupreempt_debugfs_init();
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}
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static void __exit rcupreempt_trace_cleanup(void)
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{
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debugfs_remove(statdir);
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debugfs_remove(gpdir);
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debugfs_remove(ctrsdir);
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debugfs_remove(rcudir);
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kfree(rcupreempt_trace_buf);
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}
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module_init(rcupreempt_trace_init);
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module_exit(rcupreempt_trace_cleanup);
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