Hi,

I found that today in dmesg after booting current git ( ec3b67c11df42362ccda81261d62829042f223f0 ) :

...

[  592.752777]
[  592.752781] ================================================
[  592.753478] [ BUG: lock held when returning to user space! ]
[  592.753880] ------------------------------------------------
[  592.754262] hwclock/1452 is leaving the kernel with locks still held!
[  592.754655] 1 lock held by hwclock/1452:
[  592.755007]  #0:  (&rtc->char_lock){--..}, at: [<c02a7ebb>] rtc_dev_open+0x2e/0x7e                                        

...

(gdb) l *rtc_dev_open+0x2e
0xc02a7ebb is in rtc_dev_open (drivers/rtc/rtc-dev.c:32).
27              const struct rtc_class_ops *ops = rtc->ops;
28
29              /* We keep the lock as long as the device is in use
30               * and return immediately if busy
31               */
32              if (!(mutex_trylock(&rtc->char_lock)))
33                      return -EBUSY;
34
35              file->private_data = rtc;
36
(gdb)


config is attached.

Regards,

Gabriel