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>
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arch/Kconfig
12
arch/Kconfig
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@ -353,6 +353,18 @@ config HAVE_CONTEXT_TRACKING
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config HAVE_VIRT_CPU_ACCOUNTING
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bool
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config HAVE_VIRT_CPU_ACCOUNTING_GEN
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bool
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default y if 64BIT
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help
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With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
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Before enabling this option, arch code must be audited
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to ensure there are no races in concurrent read/write of
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cputime_t. For example, reading/writing 64-bit cputime_t on
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some 32-bit arches may require multiple accesses, so proper
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locking is needed to protect against concurrent accesses.
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config HAVE_IRQ_TIME_ACCOUNTING
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bool
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help
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@ -355,6 +355,7 @@ config VIRT_CPU_ACCOUNTING_NATIVE
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config VIRT_CPU_ACCOUNTING_GEN
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bool "Full dynticks CPU time accounting"
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depends on HAVE_CONTEXT_TRACKING && 64BIT
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depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
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select VIRT_CPU_ACCOUNTING
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select CONTEXT_TRACKING
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help
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@ -101,6 +101,7 @@ config NO_HZ_FULL
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depends on HAVE_CONTEXT_TRACKING
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# VIRT_CPU_ACCOUNTING_GEN dependency
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depends on 64BIT
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depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
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select NO_HZ_COMMON
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select RCU_USER_QS
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select RCU_NOCB_CPU
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