linux-kernel - [RFC PATCH 1/6] sched: Let arch tell us if sched clock is NMI-safe

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Message-Id: <1377103341-15235-2-git-send-email-fweisbec@gmail.com>
Date:	Wed, 21 Aug 2013 18:42:16 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	John Stultz <john.stultz@...aro.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Don Zickus <dzickus@...hat.com>
Subject: [RFC PATCH 1/6] sched: Let arch tell us if sched clock is NMI-safe

sched_clock() should be fast, scalable and not use any lock. As a
resuly it should be safely called from NMIs.

Now just in case there might be some implementation details proper
to some archs that make sched_clock() not reliable or not safe in NMIs,
lets provide a way through Kconfig for archs to testify about that
support.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Don Zickus <dzickus@...hat.com>
---
 arch/Kconfig |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 1feb169..52ad235 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -393,6 +393,11 @@ config HAVE_UNDERSCORE_SYMBOL_PREFIX
 	  Some architectures generate an _ in front of C symbols; things like
 	  module loading and assembly files need to know about this.
 
+config HAVE_SCHED_CLOCK_NMI
+	bool
+	help
+	  Architecture's sched_clock() implementation is safely callable from  NMIs.
+
 #
 # ABI hall of shame
 #
-- 
1.7.5.4

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