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lockdep: Avoid /proc/lockdep & lock_stat infinite output

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Both /proc/lockdep and /proc/lock_stat output may loop infinitely.

When a read() requests an amount of data smaller than the amount of data
that the seq_file's foo_show() outputs, the output starts looping and
outputs the "stuck" element's data infinitely.  There may be multiple
sequential calls to foo_start(), foo_next()/foo_show(), and foo_stop()
for a single open with sequential read of the file.  The _start() does not
have to start with the 0th element and _show() might be called multiple
times in a row for the same element for a given open/read of the seq_file.

Also header output should not be happening in _start().  All output should
be in _show(), which SEQ_START_TOKEN is meant to help.  Having output in
_start() may also negatively impact seq_file's seq_read() and traverse()
accounting.

Signed-off-by: Tim Pepper <lnxninja@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Al Viro <viro@ftp.linux.org.uk>
This commit is contained in:
Tim Pepper 2007-10-11 22:11:11 +02:00 committed by Peter Zijlstra
parent 512e67f991
commit 94c61c0aef
1 changed files with 42 additions and 19 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

49
kernel/lockdep_proc.c
View file

@ -25,29 +25,39 @@
static void *l_next(struct seq_file *m, void *v, loff_t *pos)
{
struct lock_class *class = v;
struct lock_class *class;
(*pos)++;
if (v == SEQ_START_TOKEN)
class = m->private;
else {
class = v;
if (class->lock_entry.next != &all_lock_classes)
class = list_entry(class->lock_entry.next, struct lock_class,
lock_entry);
class = list_entry(class->lock_entry.next,
struct lock_class, lock_entry);
else
class = NULL;
m->private = class;
}
return class;
}
static void *l_start(struct seq_file *m, loff_t *pos)
{
struct lock_class *class = m->private;
struct lock_class *class;
loff_t i = 0;
if (&class->lock_entry == all_lock_classes.next)
seq_printf(m, "all lock classes:\n");
if (*pos == 0)
return SEQ_START_TOKEN;
list_for_each_entry(class, &all_lock_classes, lock_entry) {
if (++i == *pos)
return class;
}
return NULL;
}
static void l_stop(struct seq_file *m, void *v)
{
@ -101,10 +111,15 @@ static void print_name(struct seq_file *m, struct lock_class *class)
static int l_show(struct seq_file *m, void *v)
{
unsigned long nr_forward_deps, nr_backward_deps;
struct lock_class *class = m->private;
struct lock_class *class = v;
struct lock_list *entry;
char c1, c2, c3, c4;
if (v == SEQ_START_TOKEN) {
seq_printf(m, "all lock classes:\n");
return 0;
}
seq_printf(m, "%p", class->key);
#ifdef CONFIG_DEBUG_LOCKDEP
seq_printf(m, " OPS:%8ld", class->ops);
@ -523,10 +538,11 @@ static void *ls_start(struct seq_file *m, loff_t *pos)
{
struct lock_stat_seq *data = m->private;
if (data->iter == data->stats)
seq_header(m);
if (*pos == 0)
return SEQ_START_TOKEN;
if (data->iter == data->iter_end)
data->iter = data->stats + *pos;
if (data->iter >= data->iter_end)
data->iter = NULL;
return data->iter;
@ -538,8 +554,13 @@ static void *ls_next(struct seq_file *m, void *v, loff_t *pos)
(*pos)++;
if (v == SEQ_START_TOKEN)
data->iter = data->stats;
else {
data->iter = v;
data->iter++;
}
if (data->iter == data->iter_end)
data->iter = NULL;
@ -552,9 +573,11 @@ static void ls_stop(struct seq_file *m, void *v)
static int ls_show(struct seq_file *m, void *v)
{
struct lock_stat_seq *data = m->private;
if (v == SEQ_START_TOKEN)
seq_header(m);
else
seq_stats(m, v);
seq_stats(m, data->iter);
return 0;
}