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>

1 files changed, 1 insertions, 0 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 3ecd8a1178f1..68c1a0ed704d 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