[PATCH 0/4] nohz/full: drop 64-bit requirement, enable ARM support

[PATCH 0/4] nohz/full: drop 64-bit requirement, enable ARM support

[Kevin Hilman]

As of v3.10, the core ARM arch support is in mainline for NO_HZ_FULL.
The only remaining part is the removal of the hard-coded Kconfig
requirement on 64-bit platforms, which I believe can now be removed
after the nsec granularity cputime was made to work on non 64_BIT
(c.f. commit 8c23b80e, cputime_nsecs: use math64.h for nsec resolution
conversion helpers.)

This series makes the final Kconfig changes to bring NO_HZ_FULL
support to ARM.

I will queue up the arch/arm patch for Russell separately once the
generic changes are accepted.

Applies on today's linus master (commit bdbdfdef57)

Kevin

Kevin Hilman (4):
  nohz_full: Kconfig: VIRT_CPU_ACCOUNTING_GEN: drop 64-bit requirement
  nohz_full: Kconfig: drop requrement on 64-bit
  full_nohz: Kconfig: add HAVE_VIRT_CPU_ACCOUNTING_GEN
  ARM: Kconfig: allow full nohz CPU accounting

 arch/Kconfig        | 11 +++++++++++
 arch/arm/Kconfig    |  1 +
 init/Kconfig        |  3 ++-
 kernel/time/Kconfig |  2 --
 4 files changed, 14 insertions(+), 3 deletions(-)

-- 
1.8.3

[PATCH 1/4] nohz_full: Kconfig: VIRT_CPU_ACCOUNTING_GEN: drop 64-bit requirement

[Kevin Hilman]

The 64-bit requirement can be removed since the conversion of the nsec
granularity cputime to work on !64_BIT

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>
---
 init/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 18bd9e3..e9cd23b 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
 	select VIRT_CPU_ACCOUNTING
 	select CONTEXT_TRACKING
 	help
-- 
1.8.3

[PATCH 2/4] nohz_full: Kconfig: drop requrement on 64-bit

[Kevin Hilman]

Now that VIRT_CPU_ACCOUNTING_GEN no longer has a 64-bit requirement,
it can be dropped here as well.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>
---
 kernel/time/Kconfig | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 2b62fe8..a54e3e9 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -99,8 +99,6 @@ config NO_HZ_FULL
 	depends on SMP
 	# RCU_USER_QS dependency
 	depends on HAVE_CONTEXT_TRACKING
-	# VIRT_CPU_ACCOUNTING_GEN dependency
-	depends on 64BIT
 	select NO_HZ_COMMON
 	select RCU_USER_QS
 	select RCU_NOCB_CPU
-- 
1.8.3

[PATCH 3/4] full_nohz: Kconfig: add HAVE_VIRT_CPU_ACCOUNTING_GEN

[Kevin Hilman]

With HAVE_VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.  In order
to use that feature, arch code should be audited 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.

Therefore, add CONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN which arches can
enabled after they've been audited for potential races.

This option is automatically enabled on 64-bit platforms.

Feature requested by Frederic Weisbecker.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>
---
 arch/Kconfig | 11 +++++++++++
 init/Kconfig |  1 +
 2 files changed, 12 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 1feb169..3c94a2d 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -356,6 +356,17 @@ config HAVE_CONTEXT_TRACKING
 config HAVE_VIRT_CPU_ACCOUNTING
 	bool
 
+config HAVE_VIRT_CPU_ACCOUNTING_GEN
+	bool
+	default y if 64BIT
+	help
+	  With HAVE_VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit.
+	  Before enabling this option, arch code must be audited
+	  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 e9cd23b..7c283a5 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
+	depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
 	select VIRT_CPU_ACCOUNTING
 	select CONTEXT_TRACKING
 	help
-- 
1.8.3

[PATCH 4/4] ARM: Kconfig: allow full nohz CPU accounting

[Kevin Hilman]

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.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Kevin Hilman <khilman@linaro.org>
---
 arch/arm/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 3f7714d..b5e5712 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
-- 
1.8.3

Re: [PATCH 2/4] nohz_full: Kconfig: drop requrement on 64-bit

[Jean Pihet]

Hi Kevin,

FWIW typo in the title: 'requirement'.

Regards,
Jean

On Tue, Sep 17, 2013 at 12:28 AM, Kevin Hilman <khilman@linaro.org> wrote:
> Now that VIRT_CPU_ACCOUNTING_GEN no longer has a 64-bit requirement,
> it can be dropped here as well.
>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Signed-off-by: Kevin Hilman <khilman@linaro.org>
> ---
>  kernel/time/Kconfig | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
> index 2b62fe8..a54e3e9 100644
> --- a/kernel/time/Kconfig
> +++ b/kernel/time/Kconfig
> @@ -99,8 +99,6 @@ config NO_HZ_FULL
>         depends on SMP
>         # RCU_USER_QS dependency
>         depends on HAVE_CONTEXT_TRACKING
> -       # VIRT_CPU_ACCOUNTING_GEN dependency
> -       depends on 64BIT
>         select NO_HZ_COMMON
>         select RCU_USER_QS
>         select RCU_NOCB_CPU
> --
> 1.8.3
>
>
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