linux-kernel - [PATCH v2] alarmtimer: Fix unavailable wake-up source in sysfs

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Date:   Wed,  5 Jul 2017 14:08:35 +0200
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH v2] alarmtimer: Fix unavailable wake-up source in sysfs

Currently the alarmtimer registers a wake-up source unconditionally,
regardless of the system having a (wake-up capable) RTC or not.
Hence the alarmtimer will always show up in
/sys/kernel/debug/wakeup_sources, even if it is not available, and thus
cannot be a wake-up source.

To fix this, postpone registration until a wake-up capable RTC device is
added.

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
v2:
  - Move ws inside #ifdef CONFIG_RTC_CLASS to avoid a defined but not
    used warning if CONFIG_RTC_CLASS is disabled,
  - Reword.
---
 kernel/time/alarmtimer.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/time/alarmtimer.c b/kernel/time/alarmtimer.c
index e645dcc7d4ee2009..7290f45dbec8eb34 100644
--- a/kernel/time/alarmtimer.c
+++ b/kernel/time/alarmtimer.c
@@ -53,9 +53,9 @@ static ktime_t freezer_delta;
 static DEFINE_SPINLOCK(freezer_delta_lock);
 #endif
 
+#ifdef CONFIG_RTC_CLASS
 static struct wakeup_source *ws;
 
-#ifdef CONFIG_RTC_CLASS
 /* rtc timer and device for setting alarm wakeups at suspend */
 static struct rtc_timer		rtctimer;
 static struct rtc_device	*rtcdev;
@@ -86,6 +86,7 @@ static int alarmtimer_rtc_add_device(struct device *dev,
 {
 	unsigned long flags;
 	struct rtc_device *rtc = to_rtc_device(dev);
+	struct wakeup_source *__ws;
 
 	if (rtcdev)
 		return -EBUSY;
@@ -95,13 +96,20 @@ static int alarmtimer_rtc_add_device(struct device *dev,
 	if (!device_may_wakeup(rtc->dev.parent))
 		return -1;
 
+	__ws = wakeup_source_register("alarmtimer");
+
 	spin_lock_irqsave(&rtcdev_lock, flags);
 	if (!rtcdev) {
 		rtcdev = rtc;
 		/* hold a reference so it doesn't go away */
 		get_device(dev);
+		ws = __ws;
+		__ws = NULL;
 	}
 	spin_unlock_irqrestore(&rtcdev_lock, flags);
+
+	wakeup_source_unregister(__ws);
+
 	return 0;
 }
 
@@ -918,7 +926,6 @@ static int __init alarmtimer_init(void)
 		error = PTR_ERR(pdev);
 		goto out_drv;
 	}
-	ws = wakeup_source_register("alarmtimer");
 	return 0;
 
 out_drv:
-- 
2.7.4