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From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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,
	linux-api@vger.kernel.org, linux-arch@vger.kernel.org
Subject: Re: [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU
Date: Tue, 17 Mar 2015 15:08:46 +0100	[thread overview]
Message-ID: <20150317140846.GB23123@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150317113648.GC3589@linux.vnet.ibm.com>

On Tue, Mar 17, 2015 at 04:36:48AM -0700, Paul E. McKenney wrote:
> On Tue, Mar 17, 2015 at 09:18:07AM +0100, Peter Zijlstra wrote:
> > On Mon, Mar 16, 2015 at 11:37:45AM -0700, Paul E. McKenney wrote:
> > > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> > > 
> > > RCU ignores offlined CPUs, so they cannot safely run RCU read-side code.
> > > (They -can- use SRCU, but not RCU.)  This means that any use of RCU
> > > during or after the call to arch_cpu_idle_dead().  Unfortunately,
> > > commit 2ed53c0d6cc99 added a complete() call, which will contain RCU
> > > read-side critical sections if there is a task waiting to be awakened.
> > 
> > Got a little more detail there?
> 
> Quite possibly.  But exactly what sort of detail are you looking for?

What exact RCU usage you ran into that was problematic. It seems to
imply that calling complete() -- from a dead cpu -- which ends up in
try_to_wake_up() was the problem?

  reply	other threads:[~2015-03-17 14:09 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-16 18:37 [PATCH v2 tip/core/rcu 0/22] CPU hotplug updates for v4.1 Paul E. McKenney
2015-03-16 18:37 ` [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU Paul E. McKenney
2015-03-16 18:37   ` Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 02/22] x86: Use common outgoing-CPU-notification code Paul E. McKenney
2015-03-16 18:37     ` Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 03/22] blackfin: " Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 04/22] metag: " Paul E. McKenney
2015-03-16 18:37     ` Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 05/22] rcu: Consolidate offline-CPU callback initialization Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 06/22] rcu: Put all orphan-callback-related code under same comment Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 07/22] rcu: Simplify sync_rcu_preempt_exp_init() Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 08/22] rcu: Eliminate empty HOTPLUG_CPU ifdef Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 09/22] rcu: Detect stalls caused by failure to propagate up rcu_node tree Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 10/22] rcu: Provide diagnostic option to slow down grace-period initialization Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 11/22] rcutorture: Enable slow grace-period initializations Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 12/22] rcu: Remove event tracing from rcu_cpu_notify(), used by offline CPUs Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 13/22] rcu: Rework preemptible expedited bitmask handling Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 14/22] rcu: Move rcu_report_unblock_qs_rnp() to common code Paul E. McKenney
2015-03-16 18:37   ` [PATCH v2 tip/core/rcu 15/22] rcu: Process offlining and onlining only at grace-period start Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 16/22] rcu: Eliminate ->onoff_mutex from rcu_node structure Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 17/22] cpu: Make CPU-offline idle-loop transition point more precise Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 18/22] rcu: Handle outgoing CPUs on exit from idle loop Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 19/22] rcutorture: Default to grace-period-initialization delays Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 20/22] rcu: Add diagnostics to grace-period cleanup Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 21/22] rcu: Yet another fix for preemption and CPU hotplug Paul E. McKenney
2015-03-16 18:38   ` [PATCH v2 tip/core/rcu 22/22] rcu: Associate quiescent-state reports with grace period Paul E. McKenney
2015-03-17  8:18   ` [PATCH v2 tip/core/rcu 01/22] smpboot: Add common code for notification from dying CPU Peter Zijlstra
2015-03-17  8:18     ` Peter Zijlstra
2015-03-17 11:36     ` Paul E. McKenney
2015-03-17 11:36       ` Paul E. McKenney
2015-03-17 14:08       ` Peter Zijlstra [this message]
2015-03-17 16:34         ` Paul E. McKenney
2015-03-17 16:56         ` Peter Zijlstra
2015-03-17 17:32           ` Paul E. McKenney
2015-03-17 17:32             ` Paul E. McKenney

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