linux-kernel - [PATCH 21/41] nohz/cpuset: Flush cputime on threads in nohz cpusets when waiting leader

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Date:	Tue,  1 May 2012 01:54:55 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	linaro-sched-sig@...ts.linaro.org
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Ingo Molnar <mingo@...nel.org>, Kevin Hilman <khilman@...com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 21/41] nohz/cpuset: Flush cputime on threads in nohz cpusets when waiting leader

When we wait for a zombie task, flush the cputimes on nohz cpusets
in case we are waiting for a group leader that has threads running
in nohz CPUs. This way thread_group_times() doesn't report stale
values.

<doubts>
If I understood well the code, by the time we call that thread_group_times(),
we may have childs that are still running, so this is necessary.
But I need to check deeper.
</doubts>

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Alessio Igor Bogani <abogani@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Avi Kivity <avi@...hat.com>
Cc: Chris Metcalf <cmetcalf@...era.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Geoff Levand <geoff@...radead.org>
Cc: Gilad Ben Yossef <gilad@...yossef.com>
Cc: Hakan Akkan <hakanakkan@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Kevin Hilman <khilman@...com>
Cc: Max Krasnyansky <maxk@...lcomm.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephen Hemminger <shemminger@...tta.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/exit.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index 4b4042f..c194662 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -52,6 +52,7 @@
 #include <linux/hw_breakpoint.h>
 #include <linux/oom.h>
 #include <linux/writeback.h>
+#include <linux/cpuset.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -1712,6 +1713,13 @@ repeat:
 	   (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
 		goto notask;
 
+	/*
+	 * For cputime in sub-threads before adding them.
+	 * Must be called outside tasklist_lock lock because write lock
+	 * can be acquired under irqs disabled.
+	 */
+	cpuset_nohz_flush_cputimes();
+
 	set_current_state(TASK_INTERRUPTIBLE);
 	read_lock(&tasklist_lock);
 	tsk = current;
-- 
1.7.5.4

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