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authorTim Pepper <lnxninja@linux.vnet.ibm.com>2007-10-11 22:11:11 +0200
committerPeter Zijlstra <a.p.zijlstra@chello.nl>2007-10-11 22:11:11 +0200
commit94c61c0aeffe64452e742087cf803d0347ef8418 (patch)
tree95d836151d8239bb0303d4903d31b4c5180aa40b
parent512e67f991c8886de75a65b854d7c19a55fb5b8a (diff)
downloadlwn-94c61c0aeffe64452e742087cf803d0347ef8418.tar.gz
lwn-94c61c0aeffe64452e742087cf803d0347ef8418.zip
lockdep: Avoid /proc/lockdep & lock_stat infinite output
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>
-rw-r--r--kernel/lockdep_proc.c61
1 files changed, 42 insertions, 19 deletions
diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c
index c851b2dcc685..8a135bd163c2 100644
--- a/kernel/lockdep_proc.c
+++ b/kernel/lockdep_proc.c
@@ -25,28 +25,38 @@
static void *l_next(struct seq_file *m, void *v, loff_t *pos)
{
- struct lock_class *class = v;
+ struct lock_class *class;
(*pos)++;
- if (class->lock_entry.next != &all_lock_classes)
- class = list_entry(class->lock_entry.next, struct lock_class,
- lock_entry);
- else
- class = NULL;
- m->private = class;
+ 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);
+ else
+ class = NULL;
+ }
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;
- return class;
+ 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)++;
- data->iter = v;
- data->iter++;
+ 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;
}