On Tue, 2007-10-09 at 02:30 +0100, Al Viro wrote:
> On Mon, Oct 08, 2007 at 06:15:51PM -0700, Tim Pepper wrote:
> >
> > 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.
> >
> > 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)
> > + if (*pos == 0)
> > seq_printf(m, "all lock classes:\n");
>
> Do not generate output outside of ->show() and you won't have these
> problems. That's where your infinite output crap comes from.
>
> IOW, NAK - fix the underlying problem.
FWIW I had to do Tim's bits too. Just moving all output from the start
into the show method didn't fix it.
Signed-off-by: Tim Pepper <[EMAIL PROTECTED]>
Signed-off-by: Peter Zijlstra <[EMAIL PROTECTED]>
---
kernel/lockdep_proc.c | 69 +++++++++++++++++++++++---------------------------
1 file changed, 33 insertions(+), 36 deletions(-)
Index: linux-2.6/kernel/lockdep_proc.c
===================================================================
--- linux-2.6.orig/kernel/lockdep_proc.c
+++ linux-2.6/kernel/lockdep_proc.c
@@ -23,32 +23,25 @@
#include "lockdep_internals.h"
-static void *l_next(struct seq_file *m, void *v, loff_t *pos)
+static void *l_start(struct seq_file *m, loff_t *pos)
{
- struct lock_class *class = v;
-
- (*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;
+ struct lock_class *class;
+ int i = 0;
- return class;
+ list_for_each_entry(class, &all_lock_classes, lock_entry) {
+ if (i++ == *pos)
+ return class;
+ }
+ return NULL;
}
-static void *l_start(struct seq_file *m, loff_t *pos)
+static void *l_next(struct seq_file *m, void *v, loff_t *pos)
{
- struct lock_class *class = m->private;
-
- if (&class->lock_entry == all_lock_classes.next)
- seq_printf(m, "all lock classes:\n");
-
- return class;
+ (*pos)++;
+ return l_start(m, pos);
}
+
static void l_stop(struct seq_file *m, void *v)
{
}
@@ -101,10 +94,16 @@ static void print_name(struct seq_file *
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 (WARN_ON(class == NULL))
+ return 0;
+
+ if (&class->lock_entry == all_lock_classes.next)
+ seq_printf(m, "all lock classes:\n");
+
seq_printf(m, "%p", class->key);
#ifdef CONFIG_DEBUG_LOCKDEP
seq_printf(m, " OPS:%8ld", class->ops);
@@ -522,28 +521,19 @@ static void seq_header(struct seq_file *
static void *ls_start(struct seq_file *m, loff_t *pos)
{
struct lock_stat_seq *data = m->private;
+ struct lock_stat_data *iter;
- if (data->iter == data->stats)
- seq_header(m);
-
- if (data->iter == data->iter_end)
- data->iter = NULL;
+ iter = data->iter + *pos;
+ if (iter >= data->iter_end)
+ iter = NULL;
- return data->iter;
+ return iter;
}
static void *ls_next(struct seq_file *m, void *v, loff_t *pos)
{
- struct lock_stat_seq *data = m->private;
-
(*pos)++;
-
- data->iter = v;
- data->iter++;
- if (data->iter == data->iter_end)
- data->iter = NULL;
-
- return data->iter;
+ return ls_start(m, pos);
}
static void ls_stop(struct seq_file *m, void *v)
@@ -553,8 +543,15 @@ static void ls_stop(struct seq_file *m,
static int ls_show(struct seq_file *m, void *v)
{
struct lock_stat_seq *data = m->private;
+ struct lock_stat_data *iter = v;
+
+ if (WARN_ON(iter == NULL))
+ return 0;
+
+ if (iter == data->iter)
+ seq_header(m);
- seq_stats(m, data->iter);
+ seq_stats(m, iter);
return 0;
}
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