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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180/* 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 <waiman.long@hpe.com> */
/* * 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) [LOCKEVENT_ ## name] = #name,
#define LOCK_EVENTS_DIR "lock_event_counts"
/* * 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] = {
#include "lock_events_list.h"
[LOCKEVENT_reset_cnts] = ".reset_counts",};
/* * 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){ char buf[64]; int cpu, id, len; u64 sum = 0;
/* * Get the counter ID stored in file->f_inode->i_private */ id = (long)file_inode(file)->i_private;
if (id >= lockevent_num) return -EBADF;
for_each_possible_cpu(cpu) sum += per_cpu(lockevents[id], cpu); len = snprintf(buf, sizeof(buf) - 1, "%llu\n", sum);
return simple_read_from_buffer(user_buf, count, ppos, buf, len);}
/* * 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){ int cpu;
/* * Get the counter ID stored in file->f_inode->i_private */ if ((long)file_inode(file)->i_private != LOCKEVENT_reset_cnts) return count;
for_each_possible_cpu(cpu) { int i; unsigned long *ptr = per_cpu_ptr(lockevents, cpu);
for (i = 0 ; i < lockevent_num; i++) WRITE_ONCE(ptr[i], 0); } return count;}
/* * Debugfs data structures */static const struct file_operations fops_lockevent = { .read = lockevent_read, .write = lockevent_write, .llseek = default_llseek,};
#ifdef CONFIG_PARAVIRT_SPINLOCKS#include <asm/paravirt.h>
static bool __init skip_lockevent(const char *name){ static int pv_on __initdata = -1;
if (pv_on < 0) pv_on = !pv_is_native_spin_unlock(); /* * Skip PV qspinlock events on bare metal. */ if (!pv_on && !memcmp(name, "pv_", 3)) return true; return false;}#elsestatic inline bool skip_lockevent(const char *name){ return false;}#endif
/* * Initialize debugfs for the locking event counts. */static int __init init_lockevent_counts(void){ struct dentry *d_counts = debugfs_create_dir(LOCK_EVENTS_DIR, NULL); int i;
if (IS_ERR(d_counts)) goto out;
/* * Create the debugfs files * * As reading from and writing to the stat files can be slow, only * root is allowed to do the read/write to limit impact to system * performance. */ for (i = 0; i < lockevent_num; i++) { if (skip_lockevent(lockevent_names[i])) continue; if (IS_ERR(debugfs_create_file(lockevent_names[i], 0400, d_counts, (void *)(long)i, &fops_lockevent))) goto fail_undo; }
if (IS_ERR(debugfs_create_file(lockevent_names[LOCKEVENT_reset_cnts], 0200, d_counts, (void *)(long)LOCKEVENT_reset_cnts, &fops_lockevent))) goto fail_undo;
return 0;fail_undo: debugfs_remove_recursive(d_counts);out: pr_warn("Could not create '%s' debugfs entries\n", LOCK_EVENTS_DIR); return -ENOMEM;}fs_initcall(init_lockevent_counts);