• Paul E. McKenney's avatar
    time: RCU permitted to stop idle entry via softirq · 803b0eba
    Paul E. McKenney authored
    The can_stop_idle_tick() function complains if a softirq vector is
    raised too late in the idle-entry process, presumably in order to
    prevent dangling softirq invocations from being delayed across the
    full idle period, which might be indefinitely long -- and if softirq
    was asserted any later than the call to this function, such a delay
    might well happen.
    
    However, RCU needs to be able to use softirq to stop idle entry in
    order to be able to drain RCU callbacks from the current CPU, which in
    turn enables faster entry into dyntick-idle mode, which in turn reduces
    power consumption.  Because RCU takes this action at a well-defined
    point in the idle-entry path, it is safe for RCU to take this approach.
    
    This commit therefore silences the error message that is sometimes
    produced when the going-idle CPU suddenly finds that it has an RCU_SOFTIRQ
    to process.  The error message will continue to be issued for other
    softirq vectors.
    Reported-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
    Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
    Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
    803b0eba
tick-sched.c 24.1 KB