[lkml]   [2011]   [Nov]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH RFC tip/core/rcu 19/28] nohz: Allow rcu extended quiescent state handling seperately from tick stop
On Wed, Nov 02, 2011 at 09:00:03PM -0700, Josh Triplett wrote:
> On Wed, Nov 02, 2011 at 01:30:40PM -0700, Paul E. McKenney wrote:
> > From: Frederic Weisbecker <>
> >
> > 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, add two new APIs:
> > tick_nohz_idle_enter_norcu() and tick_nohz_idle_exit_norcu().
> >
> > If no use of RCU is made in the idle loop between
> > tick_nohz_enter_idle() and tick_nohz_exit_idle() calls, the arch
> > must instead call the new *_norcu() version such that the arch doesn't
> > need to call rcu_idle_enter() and rcu_idle_exit().
> The _norcu names confused me a bit. At first, I thought they meant
> "idle but not RCU idle, so you can use RCU", but from re-reading the
> commit message, apparently they mean "idle and RCU idle, so don't use
> RCU". What about something like _forbid_rcu instead? Or,
> alternatively, why not just go ahead and separate the two types of idle
> entirely rather than introducing the _norcu variants first?

Or tick_nohz_idle_enter_rcu_stop() and tick_nohz_idle_exit_rcu_restart()?

Sounds clear but too long. May be we can shorten the tick_nohz thing in the

 \ /
  Last update: 2011-11-03 12:57    [W:0.075 / U:2.916 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site