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Subject[PATCH 1/3] vtime: Add HAVE_VIRT_CPU_ACCOUNTING_GEN Kconfig
Date
From: Kevin Hilman <khilman@linaro.org>

With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. In order
to use that feature, arch code should be audited to ensure there are no
races in concurrent read/write of cputime_t. For example,
reading/writing 64-bit cputime_t on some 32-bit arches may require
multiple accesses for low and high value parts, so proper locking
is needed to protect against concurrent accesses.

Therefore, add CONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN which arches can
enable after they've been audited for potential races.

This option is automatically enabled on 64-bit platforms.

Feature requested by Frederic Weisbecker.

Signed-off-by: Kevin Hilman <khilman@linaro.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Arm Linux <linux-arm-kernel@lists.infradead.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
arch/Kconfig | 12 ++++++++++++
init/Kconfig | 1 +
kernel/time/Kconfig | 1 +
3 files changed, 14 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index af2cc6e..185f8b0 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -353,6 +353,18 @@ config HAVE_CONTEXT_TRACKING
config HAVE_VIRT_CPU_ACCOUNTING
bool

+config HAVE_VIRT_CPU_ACCOUNTING_GEN
+ bool
+ default y if 64BIT
+ help
+ With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
+ Before enabling this option, arch code must be audited
+ to ensure there are no races in concurrent read/write of
+ cputime_t. For example, reading/writing 64-bit cputime_t on
+ some 32-bit arches may require multiple accesses, so proper
+ locking is needed to protect against concurrent accesses.
+
+
config HAVE_IRQ_TIME_ACCOUNTING
bool
help
diff --git a/init/Kconfig b/init/Kconfig
index 3ecd8a1..68c1a0e 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -355,6 +355,7 @@ config VIRT_CPU_ACCOUNTING_NATIVE
config VIRT_CPU_ACCOUNTING_GEN
bool "Full dynticks CPU time accounting"
depends on HAVE_CONTEXT_TRACKING && 64BIT
+ depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
select VIRT_CPU_ACCOUNTING
select CONTEXT_TRACKING
help
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 2b62fe8..f148475 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -101,6 +101,7 @@ config NO_HZ_FULL
depends on HAVE_CONTEXT_TRACKING
# VIRT_CPU_ACCOUNTING_GEN dependency
depends on 64BIT
+ depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
select NO_HZ_COMMON
select RCU_USER_QS
select RCU_NOCB_CPU
--
1.8.3.1


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