lkml.org 
[lkml]   [2013]   [Aug]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 5/8] rcu: eliminate deadlock for rcu read site
On Mon, Aug 12, 2013 at 03:55:44PM +0200, Peter Zijlstra wrote:
> On Fri, Aug 09, 2013 at 05:31:27PM +0800, Lai Jiangshan wrote:
> > On 08/09/2013 04:40 AM, Paul E. McKenney wrote:
> > > One problem here -- it may take quite some time for a set_need_resched()
> > > to take effect. This is especially a problem for RCU priority boosting,
> > > but can also needlessly delay preemptible-RCU grace periods because
> > > local_irq_restore() and friends don't check the TIF_NEED_RESCHED bit.
> >
> >
> > The final effect of deboosting(rt_mutex_unlock()) is also accomplished
> > via set_need_resched()/set_tsk_need_resched().
> > set_need_resched() is enough for RCU priority boosting issue here.
>
> But there's a huge difference between the boosting and deboosting side
> of things. rcu_read_unlock_special() starts the boost, the deboosting
> only matters if/when you reschedule.

Or if there is a pre-existing runnable task whose priority is such that
deboosting makes it the highest-priority task.

Thanx, Paul



\
 
 \ /
  Last update: 2013-08-12 17:41    [W:0.087 / U:1.620 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site