Ubuntu
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  1. Bug #571977
  2. Comment #7

Comment 7 for bug 571977

Revision history for this message
Colin Ian King (colin-king) wrote : Re: [Lucid] Possible race condition involving rtc wakealarm when hibernating a system

I'm not entirely sure we can trust the CMOS RTC alarm state getting propagated through to the /proc/driver/rtc interface on all hardware. Perhaps one should use the rtc ioctl() interface to set/get RTC status. There is some sketchy documentation in the kernel source tree under Documentation/rtc.txt

Specifically, perhaps probing the RTC alarm date using the RTC_ALM_READ ioctl() may fetch a date that shows that the alarm has fired or not.

The documentation illustrates how to read the current alarm setting using:

        /* Read the current alarm settings */
        retval = ioctl(fd, RTC_ALM_READ, &rtc_tm);
        if (retval == -1) {
                perror("RTC_ALM_READ ioctl");
                exit(errno);
        }

        fprintf(stderr, "Alarm time now set to %02d:%02d:%02d.\n",
                rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);

Maybe this is a more reliable method rather than checking the state via /proc/driver/rtc