From 94c61c0aeffe64452e742087cf803d0347ef8418 Mon Sep 17 00:00:00 2001 From: Tim Pepper Date: Thu, 11 Oct 2007 22:11:11 +0200 Subject: 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 Signed-off-by: Peter Zijlstra Signed-off-by: Ingo Molnar Cc: Ingo Molnar Cc: Al Viro --- kernel/lockdep_proc.c | 61 +++++++++++++++++++++++++++++++++++---------------- 1 file changed, 42 insertions(+), 19 deletions(-) (limited to 'kernel/lockdep_proc.c') diff --git a/kernel/lockdep_proc.c b/kernel/lockdep_proc.c index c851b2dcc68..8a135bd163c 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; } -- cgit v1.2.3