• Jon Hunter's avatar
    nohz: Allow 32-bit machines to sleep for more than 2.15 seconds · 97813f2f
    Jon Hunter authored
    In the dynamic tick code, "max_delta_ns" (member of the
    "clock_event_device" structure) represents the maximum sleep time
    that can occur between timer events in nanoseconds.
    
    The variable, "max_delta_ns", is defined as an unsigned long
    which is a 32-bit integer for 32-bit machines and a 64-bit
    integer for 64-bit machines (if -m64 option is used for gcc).
    The value of max_delta_ns is set by calling the function
    "clockevent_delta2ns()" which returns a maximum value of LONG_MAX.
    For a 32-bit machine LONG_MAX is equal to 0x7fffffff and in
    nanoseconds this equates to ~2.15 seconds. Hence, the maximum
    sleep time for a 32-bit machine is ~2.15 seconds, where as for
    a 64-bit machine it will be many years.
    
    This patch changes the type of max_delta_ns to be "u64" instead of
    "unsigned long" so that this variable is a 64-bit type for both 32-bit
    and 64-bit machines. It also changes the maximum value returned by
    clockevent_delta2ns() to KTIME_MAX.  Hence this allows a 32-bit
    machine to sleep for longer than ~2.15 seconds. Please note that this
    patch also changes "min_delta_ns" to be "u64" too and although this is
    unnecessary, it makes the patch simpler as it avoids to fixup all
    callers of clockevent_delta2ns().
    
    [ tglx: changed "unsigned long long" to u64 as we use this data type
      	through out the time code ]
    Signed-off-by: default avatarJon Hunter <jon-hunter@ti.com>
    Cc: John Stultz <johnstul@us.ibm.com>
    LKML-Reference: <1250617512-23567-3-git-send-email-jon-hunter@ti.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    97813f2f
tick-oneshot.c 3.73 KB