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 <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Russell King <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Arm Linux <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]>
ambv · Sep 30, 2013 · 554b000 · 554b000
1 parent 15c03dd
commit 554b000
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diff --git 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
@@ -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
@@ -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