From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH v5 tip/core/rcu 15/16] rcu: Make RCU-tasks wait for idle tasks
Date: Wed, 13 Aug 2014 05:48:18 -0700 [thread overview]
Message-ID: <20140813124818.GQ4752@linux.vnet.ibm.com> (raw)
In-Reply-To: <20140813081215.GB9918@twins.programming.kicks-ass.net>
On Wed, Aug 13, 2014 at 10:12:15AM +0200, Peter Zijlstra wrote:
> On Mon, Aug 11, 2014 at 03:49:04PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> >
> > Because idle-task code may need to be patched, RCU-tasks need to wait
> > for idle tasks to schedule. This commit therefore detects this case
> > via context switch. Block CPU hotplug during this time to avoid sending
> > IPIs to offline CPUs.
> >
> > Note that checking for changes in the dyntick-idle counters is tempting,
> > but wrong. The reason that it is wrong is that a interrupt or NMI can
> > increment these counters without necessarily allowing the idle tasks to
> > make any forward progress.
>
> I'm going to NAK this.. with that rcu_idle patch I send there's
> typically only a single idle function thats out of bounds and if its
> more it can be made that with a bit of tlc to the cpuidle driver in
> question.
>
> This needs _FAR_ more justification than a maybe and a want.
Peter, your patch might be a good start, but I didn't see any reaction
from Steven or Masami and it did only x86.
Thanx, Paul
next prev parent reply other threads:[~2014-08-13 12:48 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-11 22:48 [PATCH tip/core/rcu 0/16] RCU-tasks implementation Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 01/16] rcu: Add call_rcu_tasks() Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 02/16] rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 03/16] rcu: Add synchronous grace-period waiting for RCU-tasks Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 04/16] rcu: Make TASKS_RCU handle tasks that are almost done exiting Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 05/16] rcu: Export RCU-tasks APIs to GPL modules Paul E. McKenney
2014-08-14 19:08 ` Pranith Kumar
2014-08-14 21:29 ` Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 06/16] rcutorture: Add torture tests for RCU-tasks Paul E. McKenney
2014-08-14 21:34 ` Pranith Kumar
2014-08-14 21:44 ` Paul E. McKenney
2014-08-14 21:49 ` Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 07/16] rcutorture: Add RCU-tasks test cases Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 08/16] rcu: Add stall-warning checks for RCU-tasks Paul E. McKenney
2014-08-14 21:39 ` Pranith Kumar
2014-08-14 21:59 ` Paul E. McKenney
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 09/16] rcu: Improve RCU-tasks energy efficiency Paul E. McKenney
2014-08-14 21:42 ` Pranith Kumar
2014-08-14 21:55 ` Paul E. McKenney
2014-08-14 22:00 ` Pranith Kumar
2014-08-11 22:48 ` [PATCH v5 tip/core/rcu 10/16] documentation: Add verbiage on RCU-tasks stall warning messages Paul E. McKenney
2014-08-11 22:49 ` [PATCH v5 tip/core/rcu 11/16] rcu: Defer rcu_tasks_kthread() creation till first call_rcu_tasks() Paul E. McKenney
2014-08-14 22:28 ` Pranith Kumar
2014-08-14 22:53 ` Paul E. McKenney
2014-08-11 22:49 ` [PATCH v5 tip/core/rcu 12/16] rcu: Make TASKS_RCU handle nohz_full= CPUs Paul E. McKenney
2014-08-14 22:55 ` Pranith Kumar
2014-08-14 23:16 ` Paul E. McKenney
2014-08-11 22:49 ` [PATCH v5 tip/core/rcu 13/16] rcu: Make rcu_tasks_kthread()'s GP-wait loop allow preemption Paul E. McKenney
2014-08-11 22:49 ` [PATCH v5 tip/core/rcu 14/16] rcu: Remove redundant preempt_disable() from rcu_note_voluntary_context_switch() Paul E. McKenney
2014-08-13 10:56 ` Peter Zijlstra
2014-08-13 14:07 ` Paul E. McKenney
2014-08-13 14:33 ` Peter Zijlstra
2014-08-13 20:06 ` Paul E. McKenney
2014-08-11 22:49 ` [PATCH v5 tip/core/rcu 15/16] rcu: Make RCU-tasks wait for idle tasks Paul E. McKenney
2014-08-13 8:12 ` Peter Zijlstra
2014-08-13 12:48 ` Paul E. McKenney [this message]
2014-08-13 13:40 ` Peter Zijlstra
2014-08-13 13:51 ` Steven Rostedt
2014-08-13 14:07 ` Peter Zijlstra
2014-08-13 14:13 ` Steven Rostedt
2014-08-13 14:43 ` Paul E. McKenney
2014-08-13 16:30 ` Peter Zijlstra
2014-08-13 16:43 ` Jacob Pan
2014-08-13 18:24 ` Paul E. McKenney
2014-08-13 16:35 ` Peter Zijlstra
2014-08-13 18:25 ` Paul E. McKenney
2014-08-13 14:43 ` Peter Zijlstra
2014-08-13 20:56 ` Paul E. McKenney
2014-08-13 14:12 ` Paul E. McKenney
2014-08-13 14:42 ` Peter Zijlstra
2014-08-13 17:24 ` Peter Zijlstra
2014-08-13 17:30 ` Peter Zijlstra
2014-08-13 18:16 ` Peter Zijlstra
2014-08-13 18:20 ` Paul E. McKenney
2014-08-13 18:55 ` Peter Zijlstra
2014-08-13 19:54 ` Paul E. McKenney
2014-08-11 22:49 ` [PATCH v5 tip/core/rcu 16/16] rcu: Additional information on RCU-tasks stall-warning messages Paul E. McKenney
2014-08-14 20:46 ` [PATCH v5 tip/core/rcu 01/16] rcu: Add call_rcu_tasks() Pranith Kumar
2014-08-14 21:22 ` Paul E. McKenney
2014-08-12 23:57 ` [PATCH tip/core/rcu 0/16] RCU-tasks implementation Paul E. McKenney
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