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/*
* Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition
* Internal non-public definitions that provide either classic
* or preemptible semantics.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (c) 2010 Linaro
*
* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
RCU_TRACE(long qlen); /* Number of pending CBs. */
RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
RCU_TRACE(char *name); /* Name of RCU type. */
};
/* Definition for rcupdate control block. */
static struct rcu_ctrlblk rcu_sched_ctrlblk = {
.donetail = &rcu_sched_ctrlblk.rcucblist,
.curtail = &rcu_sched_ctrlblk.rcucblist,
RCU_TRACE(.name = "rcu_sched")
};
static struct rcu_ctrlblk rcu_bh_ctrlblk = {
.donetail = &rcu_bh_ctrlblk.rcucblist,
.curtail = &rcu_bh_ctrlblk.rcucblist,
RCU_TRACE(.name = "rcu_bh")
};
#ifdef CONFIG_DEBUG_LOCK_ALLOC
int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#ifdef CONFIG_RCU_TRACE
static void check_cpu_stall(struct rcu_ctrlblk *rcp)
{
unsigned long j;
unsigned long js;
if (rcu_cpu_stall_suppress)
return;
rcp->ticks_this_gp++;
j = jiffies;
js = rcp->jiffies_stall;
if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
jiffies - rcp->gp_start, rcp->qlen);
dump_stack();
}
if (*rcp->curtail && ULONG_CMP_GE(j, js))
rcp->jiffies_stall = jiffies +
3 * rcu_jiffies_till_stall_check() + 3;
else if (ULONG_CMP_GE(j, js))
rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
}
static void check_cpu_stall_preempt(void);
#endif /* #ifdef CONFIG_RCU_TRACE */
static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
{
#ifdef CONFIG_RCU_TRACE
rcp->ticks_this_gp = 0;
rcp->gp_start = jiffies;
rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
#endif /* #ifdef CONFIG_RCU_TRACE */
}
static void check_cpu_stalls(void)
{
RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
RCU_TRACE(check_cpu_stall_preempt());
}
/*
* Because preemptible RCU does not exist, it never has any callbacks
* to process.
*/
static void rcu_preempt_process_callbacks(void)
{
}
/* Hold off callback invocation until early_initcall() time. */
static int rcu_scheduler_fully_active __read_mostly;
/*
* Start up softirq processing of callbacks.
*/
void invoke_rcu_callbacks(void)
{
if (rcu_scheduler_fully_active)
raise_softirq(RCU_SOFTIRQ);
}
#ifdef CONFIG_RCU_TRACE
/*
* There is no callback kthread, so this thread is never it.
*/
static bool rcu_is_callbacks_kthread(void)
{
return false;
}
#endif /* #ifdef CONFIG_RCU_TRACE */
static int __init rcu_scheduler_really_started(void)
{
rcu_scheduler_fully_active = 1;
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
raise_softirq(RCU_SOFTIRQ); /* Invoke any callbacks from early boot. */
return 0;
}
early_initcall(rcu_scheduler_really_started);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#include <linux/kernel_stat.h>
/*
* During boot, we forgive RCU lockdep issues. After this function is
* invoked, we start taking RCU lockdep issues seriously.
*/
void __init rcu_scheduler_starting(void)
{
WARN_ON(nr_context_switches() > 0);
rcu_scheduler_active = 1;
}
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#ifdef CONFIG_RCU_TRACE
static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
{
unsigned long flags;
local_irq_save(flags);
rcp->qlen -= n;
local_irq_restore(flags);
}
/*
* Dump statistics for TINY_RCU, such as they are.
*/
static int show_tiny_stats(struct seq_file *m, void *unused)
{
seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen);
seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen);
return 0;
}
static int show_tiny_stats_open(struct inode *inode, struct file *file)
{
return single_open(file, show_tiny_stats, NULL);
}
static const struct file_operations show_tiny_stats_fops = {
.owner = THIS_MODULE,
.open = show_tiny_stats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static struct dentry *rcudir;
static int __init rcutiny_trace_init(void)
{
struct dentry *retval;
rcudir = debugfs_create_dir("rcu", NULL);
if (!rcudir)
goto free_out;
retval = debugfs_create_file("rcudata", 0444, rcudir,
NULL, &show_tiny_stats_fops);
if (!retval)
goto free_out;
return 0;
free_out:
debugfs_remove_recursive(rcudir);
return 1;
}
static void __exit rcutiny_trace_cleanup(void)
{
debugfs_remove_recursive(rcudir);
}
module_init(rcutiny_trace_init);
module_exit(rcutiny_trace_cleanup);
MODULE_AUTHOR("Paul E. McKenney");
MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
MODULE_LICENSE("GPL");
static void check_cpu_stall_preempt(void)
{
}
#endif /* #ifdef CONFIG_RCU_TRACE */
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