linux/kernel/locking/lock_events.c

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * 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.
 *
 * Authors: Waiman Long <[email protected]>
 */

/*
 * Collect locking event counts
 */
#include <linux/debugfs.h>
#include <linux/sched.h>
#include <linux/sched/clock.h>
#include <linux/fs.h>

#include "lock_events.h"

#undef  LOCK_EVENT
#define LOCK_EVENT(name) …

#define LOCK_EVENTS_DIR …

/*
 * When CONFIG_LOCK_EVENT_COUNTS is enabled, event counts of different
 * types of locks will be reported under the <debugfs>/lock_event_counts/
 * directory. See lock_events_list.h for the list of available locking
 * events.
 *
 * Writing to the special ".reset_counts" file will reset all the above
 * locking event counts. This is a very slow operation and so should not
 * be done frequently.
 *
 * These event counts are implemented as per-cpu variables which are
 * summed and computed whenever the corresponding debugfs files are read. This
 * minimizes added overhead making the counts usable even in a production
 * environment.
 */
static const char * const lockevent_names[lockevent_num + 1] = …;

/*
 * Per-cpu counts
 */
DEFINE_PER_CPU(unsigned long, lockevents[lockevent_num]);

/*
 * The lockevent_read() function can be overridden.
 */
ssize_t __weak lockevent_read(struct file *file, char __user *user_buf,
			      size_t count, loff_t *ppos)
{ … }

/*
 * Function to handle write request
 *
 * When idx = reset_cnts, reset all the counts.
 */
static ssize_t lockevent_write(struct file *file, const char __user *user_buf,
			   size_t count, loff_t *ppos)
{ … }

/*
 * Debugfs data structures
 */
static const struct file_operations fops_lockevent = …;

#ifdef CONFIG_PARAVIRT_SPINLOCKS
#include <asm/paravirt.h>

static bool __init skip_lockevent(const char *name)
{ … }
#else
static inline bool skip_lockevent(const char *name)
{
	return false;
}
#endif

/*
 * Initialize debugfs for the locking event counts.
 */
static int __init init_lockevent_counts(void)
{ … }
fs_initcall(init_lockevent_counts);