170 lines
4.9 KiB
C
170 lines
4.9 KiB
C
/*
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* Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition
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* Internal non-public definitions that provide either classic
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* or preemptible semantics.
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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, you can access it online at
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* http://www.gnu.org/licenses/gpl-2.0.html.
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*
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* Copyright (c) 2010 Linaro
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*
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* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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*/
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#include <linux/kthread.h>
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#include <linux/init.h>
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#include <linux/debugfs.h>
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#include <linux/seq_file.h>
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/* Global control variables for rcupdate callback mechanism. */
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struct rcu_ctrlblk {
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struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
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struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
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struct rcu_head **curtail; /* ->next pointer of last CB. */
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RCU_TRACE(long qlen); /* Number of pending CBs. */
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RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
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RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
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RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
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RCU_TRACE(const char *name); /* Name of RCU type. */
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};
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/* Definition for rcupdate control block. */
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static struct rcu_ctrlblk rcu_sched_ctrlblk = {
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.donetail = &rcu_sched_ctrlblk.rcucblist,
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.curtail = &rcu_sched_ctrlblk.rcucblist,
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RCU_TRACE(.name = "rcu_sched")
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};
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static struct rcu_ctrlblk rcu_bh_ctrlblk = {
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.donetail = &rcu_bh_ctrlblk.rcucblist,
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.curtail = &rcu_bh_ctrlblk.rcucblist,
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RCU_TRACE(.name = "rcu_bh")
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};
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#include <linux/kernel_stat.h>
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int rcu_scheduler_active __read_mostly;
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EXPORT_SYMBOL_GPL(rcu_scheduler_active);
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/*
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* During boot, we forgive RCU lockdep issues. After this function is
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* invoked, we start taking RCU lockdep issues seriously. Note that unlike
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* Tree RCU, Tiny RCU transitions directly from RCU_SCHEDULER_INACTIVE
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* to RCU_SCHEDULER_RUNNING, skipping the RCU_SCHEDULER_INIT stage.
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* The reason for this is that Tiny RCU does not need kthreads, so does
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* not have to care about the fact that the scheduler is half-initialized
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* at a certain phase of the boot process.
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*/
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void __init rcu_scheduler_starting(void)
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{
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WARN_ON(nr_context_switches() > 0);
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rcu_scheduler_active = RCU_SCHEDULER_RUNNING;
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}
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#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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#ifdef CONFIG_RCU_TRACE
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static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
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{
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unsigned long flags;
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local_irq_save(flags);
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rcp->qlen -= n;
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local_irq_restore(flags);
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}
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/*
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* Dump statistics for TINY_RCU, such as they are.
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*/
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static int show_tiny_stats(struct seq_file *m, void *unused)
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{
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seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen);
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seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen);
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return 0;
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}
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static int show_tiny_stats_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_tiny_stats, NULL);
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}
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static const struct file_operations show_tiny_stats_fops = {
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.owner = THIS_MODULE,
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.open = show_tiny_stats_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static struct dentry *rcudir;
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static int __init rcutiny_trace_init(void)
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{
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struct dentry *retval;
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rcudir = debugfs_create_dir("rcu", NULL);
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if (!rcudir)
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goto free_out;
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retval = debugfs_create_file("rcudata", 0444, rcudir,
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NULL, &show_tiny_stats_fops);
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if (!retval)
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goto free_out;
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return 0;
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free_out:
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debugfs_remove_recursive(rcudir);
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return 1;
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}
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device_initcall(rcutiny_trace_init);
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static void check_cpu_stall(struct rcu_ctrlblk *rcp)
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{
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unsigned long j;
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unsigned long js;
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if (rcu_cpu_stall_suppress)
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return;
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rcp->ticks_this_gp++;
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j = jiffies;
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js = READ_ONCE(rcp->jiffies_stall);
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if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {
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pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
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rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE,
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jiffies - rcp->gp_start, rcp->qlen);
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dump_stack();
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WRITE_ONCE(rcp->jiffies_stall,
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jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
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} else if (ULONG_CMP_GE(j, js)) {
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WRITE_ONCE(rcp->jiffies_stall,
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jiffies + rcu_jiffies_till_stall_check());
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}
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}
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static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
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{
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rcp->ticks_this_gp = 0;
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rcp->gp_start = jiffies;
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WRITE_ONCE(rcp->jiffies_stall,
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jiffies + rcu_jiffies_till_stall_check());
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}
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static void check_cpu_stalls(void)
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{
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RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
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RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
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}
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#endif /* #ifdef CONFIG_RCU_TRACE */
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