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 <[email protected]>
----
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
On Wed 2018-04-25 18:59:31, 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.
Sounds like magic.
> -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)
> {
...
> - 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_stop(struct seq_file *m, void *v)
> +{
> + int *srcuidx = m->private;
> +
> + srcu_read_unlock(&wakeup_srcu, *srcuidx);
> +}
But you are holding srcu_lock over return to userspace, and somehow I
don't think that's permitted?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Hi, Pavel
Thanks for your review.
2018-04-29 22:30 GMT+08:00 Pavel Machek <[email protected]>:
> On Wed 2018-04-25 18:59:31, 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.
>
> Sounds like magic.
I did not explain clearly here.
If we use single_open() to open the file, a single buffer(physical
continious) will be allocated
to store the whole data of file /sys/kernel/debug/wakeup_sources.
When memory situation is not good(fragments...), long time may be used
to allocate
such buffer which may cause android watchdog timeout.
>
>> -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)
>> {
> ...
>> - 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_stop(struct seq_file *m, void *v)
>> +{
>> + int *srcuidx = m->private;
>> +
>> + srcu_read_unlock(&wakeup_srcu, *srcuidx);
>> +}
>
> But you are holding srcu_lock over return to userspace, and somehow I
> don't think that's permitted?
In seq_read(), the m->op->[start | stop] will be invoked as a pair.
So the srcu_lock will not be hold and return to userspace.
Thanks.
> Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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 <[email protected]>
> ----
> 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!