Re: [PATCH 2/4] nohz: Split extended quiescent state handling fromnohz switch
From: David Miller
Date: Mon Jun 06 2011 - 00:01:38 EST
From: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Date: Mon, 6 Jun 2011 05:10:56 +0200
> It is assumed that rcu won't be used once we switch to tickless
> mode and until we restart the tick. However this is not always
> true, as in x86-64 where we dereference the idle notifiers after
> the tick is stopped.
> To prepare for fixing this, split the tickless mode switching and
> RCU extended quiescent state logics.
> Make tick_nohz_stop/restart_sched_tick() RCU agnostic but provide
> a new pair of APIs tick_nohz_enter/exit_idle() that keep the
> old behaviour by handling both the nohz mode and RCU extended
> quiescent states, then convert every archs to use these.
> Archs that want to switch to extended QS to some custom points
> can do it later by using tick_nohz_stop_sched_tick() and
> rcu_enter_nohz() seperately.
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Acked-by: David S. Miller <davem@xxxxxxxxxxxxx>
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