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alarmtimer: Ensure RTC module is not unloaded

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When registering the rtc device to be used to handle alarm timers,
get_device is used to ensure the device doesn't go away but the module can
still be unloaded.

Call try_module_get to ensure the rtc driver will not go away.

Reported-and-tested-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Link: http://lkml.kernel.org/r/20170820220146.30969-1-alexandre.belloni@free-electrons.com
This commit is contained in:
Alexandre Belloni 2017-08-21 00:01:46 +02:00 committed by Thomas Gleixner
parent bc30658eff
commit 51218298a2
1 changed files with 6 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

6
kernel/time/alarmtimer.c
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@ -28,6 +28,7 @@
#include <linux/workqueue.h> #include <linux/workqueue.h>
#include <linux/freezer.h> #include <linux/freezer.h>
#include <linux/compat.h> #include <linux/compat.h>
#include <linux/module.h>
#include "posix-timers.h" #include "posix-timers.h"
@ -103,6 +104,11 @@ static int alarmtimer_rtc_add_device(struct device *dev,
spin_lock_irqsave(&rtcdev_lock, flags); spin_lock_irqsave(&rtcdev_lock, flags);
if (!rtcdev) { if (!rtcdev) {
if (!try_module_get(rtc->owner)) {
spin_unlock_irqrestore(&rtcdev_lock, flags);
return -1;
}
rtcdev = rtc; rtcdev = rtc;
/* hold a reference so it doesn't go away */ /* hold a reference so it doesn't go away */
get_device(dev); get_device(dev);