Re: [PATCH v3] PM / wakeup: use seq_open() to show wakeup stats

Rafael J. Wysocki
2018-05-13T08:46:57Z

On Wednesday, April 25, 2018 12:59:31 PM CEST Ganesh Mahendran wrote:
> single_open() interface requires that the whole output must
> fit into a single buffer. This will lead to timeout when
> system memory is not in a good situation.
>
> This patch use seq_open() to show wakeup stats. This method
> need only one page, so timeout will not be observed.
>
> Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
> ----
> v3: simplify wakeup_sources_stats_seq_start
> v2: use srcu_read_lock instead of rcu_read_lock
> ---
> drivers/base/power/wakeup.c | 75 +++++++++++++++++++++++++++++++++++----------
> 1 file changed, 59 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> index ea01621..5872705 100644
> --- a/drivers/base/power/wakeup.c
> +++ b/drivers/base/power/wakeup.c
> @@ -1029,32 +1029,75 @@ static int print_wakeup_source_stats(struct seq_file *m,
> return 0;
> }
>
> -/**
> - * wakeup_sources_stats_show - Print wakeup sources statistics information.
> - * @m: seq_file to print the statistics into.
> - */
> -static int wakeup_sources_stats_show(struct seq_file *m, void *unused)
> +static void *wakeup_sources_stats_seq_start(struct seq_file *m,
> + loff_t *pos)
> {
> struct wakeup_source *ws;
> - int srcuidx;
> + loff_t n = *pos;
> + int *srcuidx = m->private;
>
> - seq_puts(m, "name\t\tactive_count\tevent_count\twakeup_count\t"
> - "expire_count\tactive_since\ttotal_time\tmax_time\t"
> - "last_change\tprevent_suspend_time\n");
> + if (n == 0) {
> + seq_puts(m, "name\t\tactive_count\tevent_count\twakeup_count\t"
> + "expire_count\tactive_since\ttotal_time\tmax_time\t"
> + "last_change\tprevent_suspend_time\n");
> + }
>
> - srcuidx = srcu_read_lock(&wakeup_srcu);
> - list_for_each_entry_rcu(ws, &wakeup_sources, entry)
> - print_wakeup_source_stats(m, ws);
> - srcu_read_unlock(&wakeup_srcu, srcuidx);
> + *srcuidx = srcu_read_lock(&wakeup_srcu);
> + list_for_each_entry_rcu(ws, &wakeup_sources, entry) {
> + if (n-- <= 0)
> + return ws;
> + }
> +
> + return NULL;
> +}
> +
> +static void *wakeup_sources_stats_seq_next(struct seq_file *m,
> + void *v, loff_t *pos)
> +{
> + struct wakeup_source *ws = v;
> + struct wakeup_source *next_ws = NULL;
> +
> + ++(*pos);
>
> - print_wakeup_source_stats(m, &deleted_ws);
> + list_for_each_entry_continue_rcu(ws, &wakeup_sources, entry) {
> + next_ws = ws;
> + break;
> + }
> +
> + return next_ws;
> +}
> +
> +static void wakeup_sources_stats_seq_stop(struct seq_file *m, void *v)
> +{
> + int *srcuidx = m->private;
> +
> + srcu_read_unlock(&wakeup_srcu, *srcuidx);
> +}
> +
> +/**
> + * wakeup_sources_stats_seq_show - Print wakeup sources statistics information.
> + * @m: seq_file to print the statistics into.
> + * @v: wakeup_source of each iteration
> + */
> +static int wakeup_sources_stats_seq_show(struct seq_file *m, void *v)
> +{
> + struct wakeup_source *ws = v;
> +
> + print_wakeup_source_stats(m, ws);
>
> return 0;
> }
>
> +static const struct seq_operations wakeup_sources_stats_seq_ops = {
> + .start = wakeup_sources_stats_seq_start,
> + .next = wakeup_sources_stats_seq_next,
> + .stop = wakeup_sources_stats_seq_stop,
> + .show = wakeup_sources_stats_seq_show,
> +};
> +
> static int wakeup_sources_stats_open(struct inode *inode, struct file *file)
> {
> - return single_open(file, wakeup_sources_stats_show, NULL);
> + return seq_open_private(file, &wakeup_sources_stats_seq_ops, sizeof(int));
> }
>
> static const struct file_operations wakeup_sources_stats_fops = {
> @@ -1062,7 +1105,7 @@ static int wakeup_sources_stats_open(struct inode *inode, struct file *file)
> .open = wakeup_sources_stats_open,
> .read = seq_read,
> .llseek = seq_lseek,
> - .release = single_release,
> + .release = seq_release_private,
> };
>
> static int __init wakeup_sources_debugfs_init(void)
>

Applied, thanks!