• Heiko Carstens's avatar
    s390/time: fix sched_clock() overflow · ed4f2094
    Heiko Carstens authored
    Converting a 64 Bit TOD format value to nanoseconds means that the value
    must be divided by 4.096. In order to achieve that we multiply with 125
    and divide by 512.
    When used within sched_clock() this triggers an overflow after appr.
    417 days. Resulting in a sched_clock() return value that is much smaller
    than previously and therefore may cause all sort of weird things in
    subsystems that rely on a monotonic sched_clock() behaviour.
    
    To fix this implement a tod_to_ns() helper function which converts TOD
    values without overflow and call this function from both places that
    open coded the conversion: sched_clock() and kvm_s390_handle_wait().
    
    Cc: stable@kernel.org
    Reviewed-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    ed4f2094
time.c 45.8 KB