Commit 554b0004 authored by Kevin Hilman's avatar Kevin Hilman Committed by Frederic Weisbecker
Browse files

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: default avatarKevin 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: default avatarFrederic Weisbecker <fweisbec@gmail.com>
parent 15c03dd4

arch/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -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

init/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

kernel/time/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

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