vtime: Add HAVE_VIRT_CPU_ACCOUNTING_GEN Kconfig

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>

diff --git a/arch/Kconfig b/arch/Kconfig
index af2cc6eabcc781c4e8f7ee2067de75844ed5874d..185f8b0076436d75fb6896855cd2c4df0d1ed73c 100644 (file)
--- 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 3ecd8a1178f102d832cdf3b4af0a908997ea648b..68c1a0ed704dc66053b98fc138032c30d3e143d2 100644 (file)
--- 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 2b62fe86f9eccf828846511dbfca8f20a4109321..f148475e51945ddf84facecb5c9300a76064bd69 100644 (file)
--- 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