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    SubjectRe: [PATCH] time: tick-sched: use bool for tick_stopped
    On Tue, Apr 10, 2018 at 06:07:17PM +0800, yuankuiz@codeaurora.org wrote:
    > > > > > @@ -48,8 +48,8 @@ struct tick_sched {
    > > > > > unsigned long check_clocks;
    > > > > > enum tick_nohz_mode nohz_mode;
    > > > > >
    > > > > > + bool tick_stopped : 1;
    > > > > > unsigned int inidle : 1;
    > > > > > - unsigned int tick_stopped : 1;
    > > > > > unsigned int idle_active : 1;
    > > > > > unsigned int do_timer_last : 1;
    > > > > > unsigned int got_idle_tick : 1;
    > > > >
    > > > > I don't think this is a good idea at all.
    > > > >
    > > > > Please see https://lkml.org/lkml/2017/11/21/384 for example.
    > > > [ZJ] Thanks for this sharing. Looks like, this patch fall into the
    > > > case of
    > > > "Maybe".
    > >
    > > This patch falls into the case 'pointless' because it adds extra storage
    > [ZJ] 1 bit vs 1 bit. no more.

    Since its a different type, the bitfields will not be merged. Also I'm
    surprised a bitfield with base-type _Bool is even allowed.

    > > for no benefit at all.
    > [ZJ] tick_stopped is returned by the tick_nohz_tick_stopped() which is bool.
    > The benefit is no any potiential type conversion could be minded.

    Do you have any actual evidence for that? Is there a compiler stupid
    enough to generate code to convert a bool to a 1bit value?

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