From 554b0004d0ec4fbd11e08668dfc400f211e8d5c5 Mon Sep 17 00:00:00 2001 From: Kevin Hilman Date: Mon, 16 Sep 2013 15:28:21 -0700 Subject: [PATCH 1/3] 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 Cc: Ingo Molnar Cc: Russell King Cc: Paul E. McKenney Cc: Arm Linux Signed-off-by: Frederic Weisbecker --- arch/Kconfig | 12 ++++++++++++ init/Kconfig | 1 + kernel/time/Kconfig | 1 + 3 files changed, 14 insertions(+) diff --git a/arch/Kconfig b/arch/Kconfig index af2cc6eabcc7..185f8b007643 100644 --- 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 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 diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index 2b62fe86f9ec..f148475e5194 100644 --- 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 From ff3fb2541246a83ce56c61d14df30b7a22e4302b Mon Sep 17 00:00:00 2001 From: Kevin Hilman Date: Mon, 16 Sep 2013 15:28:19 -0700 Subject: [PATCH 2/3] nohz: Drop generic vtime obsolete dependency on CONFIG_64BIT The CONFIG_64BIT requirement on vtime can finally be removed since we now depend on HAVE_VIRT_CPU_ACCOUNTING_GEN which already takes care of the arch ability to handle nsecs based cputime_t safely. Signed-off-by: Kevin Hilman Cc: Ingo Molnar Cc: Russell King Cc: Paul E. McKenney Cc: Arm Linux Signed-off-by: Frederic Weisbecker --- init/Kconfig | 2 +- kernel/time/Kconfig | 1 - 2 files changed, 1 insertion(+), 2 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 68c1a0ed704d..841e79cb8bb3 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -354,7 +354,7 @@ 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_CONTEXT_TRACKING depends on HAVE_VIRT_CPU_ACCOUNTING_GEN select VIRT_CPU_ACCOUNTING select CONTEXT_TRACKING diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig index f148475e5194..3ce6e8c5f3fc 100644 --- a/kernel/time/Kconfig +++ b/kernel/time/Kconfig @@ -100,7 +100,6 @@ config NO_HZ_FULL # RCU_USER_QS dependency 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 From 31c1fc8187158cb80ccd57c19e024c55af901797 Mon Sep 17 00:00:00 2001 From: Kevin Hilman Date: Mon, 16 Sep 2013 15:28:22 -0700 Subject: [PATCH 3/3] ARM: Kconfig: allow full nohz CPU accounting With the 64-bit requirement removed from VIRT_CPU_ACCOUNTING_GEN, allow ARM platforms to enable it. Since VIRT_CPU_ACCOUNTING_GEN is a dependency for full NO_HZ, this allows ARM platforms to enable full NO_HZ as well. Signed-off-by: Kevin Hilman Cc: Ingo Molnar Cc: Russell King Cc: Paul E. McKenney Cc: Arm Linux Signed-off-by: Frederic Weisbecker --- arch/arm/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 1ad6fb6c094d..323baf07fdce 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -54,6 +54,7 @@ config ARM select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_SYSCALL_TRACEPOINTS select HAVE_UID16 + select HAVE_VIRT_CPU_ACCOUNTING_GEN select IRQ_FORCED_THREADING select KTIME_SCALAR select MODULES_USE_ELF_REL