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SubjectRe: [PATCH] pm / wakeup: simplify the output logic of pm_show_wakelocks()
On Thu, 13 Jan 2022, Greg Kroah-Hartman wrote:

> The buffer handling in pm_show_wakelocks() is tricky, and hopefully
> correct. Ensure it really is correct by using sysfs_emit_at() which
> handles all of the tricky string handling logic in a PAGE_SIZE buffer
> for us automatically as this is a sysfs file being read from.
>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Pavel Machek <pavel@ucw.cz>
> Cc: Len Brown <len.brown@intel.com>
> Cc: linux-pm@vger.kernel.org
> Cc: Lee Jones <lee.jones@linaro.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> kernel/power/wakelock.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)

Reviewed-by: Lee Jones <lee.jones@linaro.org>

> diff --git a/kernel/power/wakelock.c b/kernel/power/wakelock.c
> index 105df4dfc783..52571dcad768 100644
> --- a/kernel/power/wakelock.c
> +++ b/kernel/power/wakelock.c
> @@ -39,23 +39,20 @@ ssize_t pm_show_wakelocks(char *buf, bool show_active)
> {
> struct rb_node *node;
> struct wakelock *wl;
> - char *str = buf;
> - char *end = buf + PAGE_SIZE;
> + int len = 0;
>
> mutex_lock(&wakelocks_lock);
>
> for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
> wl = rb_entry(node, struct wakelock, node);
> if (wl->ws->active == show_active)
> - str += scnprintf(str, end - str, "%s ", wl->name);
> + len += sysfs_emit_at(buf, len, "%s ", wl->name);
> }
> - if (str > buf)
> - str--;
>
> - str += scnprintf(str, end - str, "\n");
> + len += sysfs_emit_at(buf, len, "\n");
>
> mutex_unlock(&wakelocks_lock);
> - return (str - buf);
> + return len;
> }
>
> #if CONFIG_PM_WAKELOCKS_LIMIT > 0

--
Lee Jones [李琼斯]
Principal Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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