rtc: cmos: Cancel alarm timer if alarm time is equal to now+1 seconds
Steps to reproduce the problem:
1) Enable RTC wake-up option in BIOS Setup
2) Issue one of these commands in the OS: "poweroff"
or "shutdown -h now"
3) System will shut down and then reboot automatically
Root-cause of the issue:
1) During the shutdown process, the hwclock utility is used
to save the system clock to hardware clock (RTC).
2) The hwclock utility invokes ioctl() with RTC_UIE_ON. The
kernel configures the RTC alarm for the periodic interrupt
(every 1 second).
3) The hwclock uitlity closes the /dev/rtc0 device, and the
kernel disables the RTC alarm irq (AIE bit of Register B)
via ioctl() with RTC_UIE_OFF. But, the configured alarm
time is the current_time + 1.
4) After the next 1 second is elapsed, the AF (alarm
interrupt flag) of Register C is set.
5) The S5 handler in BIOS is invoked to configure alarm
registers (enable AIE bit and configure alarm date/time).
But, BIOS does not clear the previous interrupt status
during alarm configuration. Therefore, "AF=AIE=1" causes
the rtc device to trigger an interrupt.
6) So, the machine reboots automatically right after shutdown.
This patch cancels the alarm timer if the following condictions are
met (suggested by Alexandre):
1) The configured alarm time is equal to current_time + 1
seconds.
2) The AIE timer is not in use.
The member 'alarm_expires' is introduced in struct cmos_rtc because
of the following reasons:
1) The configured alarm time can be retrieved from
cmos_read_alarm(), but we need to take the 'wrapped
timestamp' and 'time rollover' into consideration. The
function __rtc_read_alarm() eliminates the concerns. To
avoid the duplicated code in the lower level RTC driver,
invoking __rtc_read_alarm from the lower level RTC driver
is not encouraged. Moreover, the compilation error 'the
undefined __rtc_read_alarm" is observed if the lower level
RTC driver is compiled as a kernel module.
2) The uie_rtctimer.node.expires and aie_timer.node.expires can
be retrieved for the configured alarm time. But, the problem
is that either of them might configure the CMOS alarm time.
We cannot make sure UIE timer or AIE tiemr configured the
CMOS alarm time before. (uie_rtctimer or aie_timer is enabled
and then is disabled).
3) The patch introduces the member 'alarm_expires' to keep the
newly configured alarm time, so the above-mentioned concerns
can be eliminated.
The issue goes away after 20-time shutdown tests.
Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
Tested-by: Egbert Eich <eich@suse.de>
Tested-by: Diego Ercolani <diego.ercolani@gmail.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
1 file changed