Messages in this thread | | | Date | Fri, 25 Nov 2016 00:34:26 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 2/2] rcu: Force resched_cpu when jiffies >= rcu_state.jiffies_resched |
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On Tue, Nov 22, 2016 at 05:12:20PM +0900, Byungchul Park wrote: > On Wed, Nov 09, 2016 at 03:32:15PM +0900, Byungchul Park wrote: > > Currently rcu code forces CPU into scheduler when jiffies >= > > rcu_state.gp_start + jiffies_till_sched_qs, via resched_cpu(). > > > > It would be better to force CPU into scheduler when jiffies >= > > rcu_state.jiffies_resched, too. > > Hello, > > I think these two patches are necessary to call resched_cpu() even in > case of jiffies >= rcu_state.jiffies_resched, too. Am I wrong? > > It would be appriciated if you let me know if I was wrong.
My current thought is that both the "if" statement and the call to resched_cpu() should be removed, but I am still testing and working through the timing.
Either way, I do very much appreciate your having called my attention to this code!
Thanx, Paul
> Thank you, > Byungchul > > > > > Signed-off-by: Byungchul Park <byungchul.park@lge.com> > > --- > > kernel/rcu/tree.c | 5 ++--- > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index d8e8859..287f468 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -1217,11 +1217,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, > > READ_ONCE(*rcrmp) + rdp->rsp->flavor_mask); > > } > > rdp->rsp->jiffies_resched += 5; /* Re-enable beating. */ > > - } > > > > - /* And if it has been a really long time, kick the CPU as well. */ > > - if (ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs)) > > + /* And if it has been a really long time, kick the CPU as well. */ > > resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ > > + } > > > > return 0; > > } > > -- > > 1.9.1 >
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