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![Hugh Dickins](/assets/img/avatar_default.png)
Miles Lane tailing /sys files hit a BUG which Pekka Enberg has tracked
to my 966c8c12dc
sprint_symbol(): use
less stack exposing a bug in slub's list_locations() -
kallsyms_lookup() writes a 0 to namebuf[KSYM_NAME_LEN-1], but that was
beyond the end of page provided.
The 100 slop which list_locations() allows at end of page looks roughly
enough for all the other stuff it might print after the symbol before
it checks again: break out KSYM_SYMBOL_LEN earlier than before.
Latencytop and ftrace and are using KSYM_NAME_LEN buffers where they
need KSYM_SYMBOL_LEN buffers, and vmallocinfo a 2*KSYM_NAME_LEN buffer
where it wants a KSYM_SYMBOL_LEN buffer: fix those before anyone copies
them.
[akpm@linux-foundation.org: ftrace.h needs module.h]
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc Miles Lane <miles.lane@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
239 lines
5.2 KiB
C
239 lines
5.2 KiB
C
/*
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* latencytop.c: Latency display infrastructure
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*
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* (C) Copyright 2008 Intel Corporation
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* Author: Arjan van de Ven <arjan@linux.intel.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*/
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#include <linux/latencytop.h>
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#include <linux/kallsyms.h>
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#include <linux/seq_file.h>
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#include <linux/notifier.h>
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#include <linux/spinlock.h>
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#include <linux/proc_fs.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/stacktrace.h>
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static DEFINE_SPINLOCK(latency_lock);
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#define MAXLR 128
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static struct latency_record latency_record[MAXLR];
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int latencytop_enabled;
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void clear_all_latency_tracing(struct task_struct *p)
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{
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unsigned long flags;
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if (!latencytop_enabled)
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return;
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spin_lock_irqsave(&latency_lock, flags);
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memset(&p->latency_record, 0, sizeof(p->latency_record));
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p->latency_record_count = 0;
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spin_unlock_irqrestore(&latency_lock, flags);
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}
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static void clear_global_latency_tracing(void)
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{
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unsigned long flags;
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spin_lock_irqsave(&latency_lock, flags);
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memset(&latency_record, 0, sizeof(latency_record));
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spin_unlock_irqrestore(&latency_lock, flags);
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}
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static void __sched
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account_global_scheduler_latency(struct task_struct *tsk, struct latency_record *lat)
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{
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int firstnonnull = MAXLR + 1;
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int i;
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if (!latencytop_enabled)
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return;
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/* skip kernel threads for now */
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if (!tsk->mm)
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return;
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for (i = 0; i < MAXLR; i++) {
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int q, same = 1;
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/* Nothing stored: */
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if (!latency_record[i].backtrace[0]) {
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if (firstnonnull > i)
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firstnonnull = i;
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continue;
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}
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for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
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unsigned long record = lat->backtrace[q];
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if (latency_record[i].backtrace[q] != record) {
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same = 0;
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break;
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}
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/* 0 and ULONG_MAX entries mean end of backtrace: */
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if (record == 0 || record == ULONG_MAX)
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break;
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}
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if (same) {
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latency_record[i].count++;
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latency_record[i].time += lat->time;
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if (lat->time > latency_record[i].max)
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latency_record[i].max = lat->time;
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return;
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}
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}
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i = firstnonnull;
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if (i >= MAXLR - 1)
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return;
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/* Allocted a new one: */
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memcpy(&latency_record[i], lat, sizeof(struct latency_record));
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}
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static inline void store_stacktrace(struct task_struct *tsk, struct latency_record *lat)
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{
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struct stack_trace trace;
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memset(&trace, 0, sizeof(trace));
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trace.max_entries = LT_BACKTRACEDEPTH;
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trace.entries = &lat->backtrace[0];
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trace.skip = 0;
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save_stack_trace_tsk(tsk, &trace);
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}
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void __sched
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account_scheduler_latency(struct task_struct *tsk, int usecs, int inter)
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{
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unsigned long flags;
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int i, q;
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struct latency_record lat;
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if (!latencytop_enabled)
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return;
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/* Long interruptible waits are generally user requested... */
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if (inter && usecs > 5000)
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return;
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memset(&lat, 0, sizeof(lat));
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lat.count = 1;
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lat.time = usecs;
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lat.max = usecs;
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store_stacktrace(tsk, &lat);
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spin_lock_irqsave(&latency_lock, flags);
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account_global_scheduler_latency(tsk, &lat);
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/*
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* short term hack; if we're > 32 we stop; future we recycle:
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*/
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tsk->latency_record_count++;
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if (tsk->latency_record_count >= LT_SAVECOUNT)
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goto out_unlock;
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for (i = 0; i < LT_SAVECOUNT ; i++) {
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struct latency_record *mylat;
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int same = 1;
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mylat = &tsk->latency_record[i];
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for (q = 0 ; q < LT_BACKTRACEDEPTH ; q++) {
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unsigned long record = lat.backtrace[q];
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if (mylat->backtrace[q] != record) {
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same = 0;
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break;
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}
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/* 0 and ULONG_MAX entries mean end of backtrace: */
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if (record == 0 || record == ULONG_MAX)
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break;
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}
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if (same) {
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mylat->count++;
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mylat->time += lat.time;
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if (lat.time > mylat->max)
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mylat->max = lat.time;
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goto out_unlock;
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}
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}
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/* Allocated a new one: */
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i = tsk->latency_record_count;
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memcpy(&tsk->latency_record[i], &lat, sizeof(struct latency_record));
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out_unlock:
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spin_unlock_irqrestore(&latency_lock, flags);
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}
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static int lstats_show(struct seq_file *m, void *v)
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{
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int i;
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seq_puts(m, "Latency Top version : v0.1\n");
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for (i = 0; i < MAXLR; i++) {
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if (latency_record[i].backtrace[0]) {
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int q;
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seq_printf(m, "%i %li %li ",
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latency_record[i].count,
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latency_record[i].time,
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latency_record[i].max);
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for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
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char sym[KSYM_SYMBOL_LEN];
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char *c;
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if (!latency_record[i].backtrace[q])
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break;
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if (latency_record[i].backtrace[q] == ULONG_MAX)
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break;
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sprint_symbol(sym, latency_record[i].backtrace[q]);
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c = strchr(sym, '+');
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if (c)
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*c = 0;
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seq_printf(m, "%s ", sym);
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}
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seq_printf(m, "\n");
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}
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}
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return 0;
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}
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static ssize_t
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lstats_write(struct file *file, const char __user *buf, size_t count,
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loff_t *offs)
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{
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clear_global_latency_tracing();
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return count;
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}
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static int lstats_open(struct inode *inode, struct file *filp)
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{
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return single_open(filp, lstats_show, NULL);
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}
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static struct file_operations lstats_fops = {
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.open = lstats_open,
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.read = seq_read,
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.write = lstats_write,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int __init init_lstats_procfs(void)
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{
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proc_create("latency_stats", 0644, NULL, &lstats_fops);
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return 0;
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}
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__initcall(init_lstats_procfs);
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