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Subject[PATCH v3] PM / wakeup: use seq_open() to show wakeup stats
Date
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)
--
1.9.1
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