As of v3.10, the core ARM 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.
Series applies to v3.10.
I will queue up the arch/arm patch for Russell separately once the generic changes are accepted.
Kevin
arch/arm/Kconfig | 1 + init/Kconfig | 2 +- kernel/time/Kconfig | 2 -- 3 files changed, 2 insertions(+), 3 deletions(-)
The current 64-bit dependency is on VIRT_CPU_ACCOUNTING_GEN, which already has its own dependency on 64-bit. Remove it from NO_HZ_FULL.
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 70f27e8..b78760f 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
On Wed, Jul 03, 2013 at 11:36:39AM -0700, Kevin Hilman wrote:
The current 64-bit dependency is on VIRT_CPU_ACCOUNTING_GEN, which already has its own dependency on 64-bit. Remove it from NO_HZ_FULL.
It's not exactly redundant. It's a necessary dependency inheritance. When we select NO_HZ_FULL, TICK_CPU_ACCOUNTING and VIRT_CPU_ACCOUNTING_NATIVE disappear such that only VIRT_CPU_ACCOUNTING_GEN can be selected. But if we don't have CONFIG_64bits, then VIRT_CPU_ACCOUNTING_GEN is not possible either. So we end up with nothing for the accounting (or whatever random reaction from Kconfig against that situation) and that's a bug. So we need to inherit the 64 bits dependency on NO_HZ_FULL to prevent that.
We can remove this dependency from NO_HZ_FULL, but only once we remove it from VIRT_CPU_ACCOUNTING_GEN, not the other way around otherwise this breaks bisection.
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 70f27e8..b78760f 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
The 64-bit requirement can be removed after the conversion of the nsec granularity cputime to work on !64_BIT, which was done in commit 8c23b80e (cputime_nsecs: use math64.h for nsec resolution conversion helpers)
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 2d9b831..e151022 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -325,7 +325,7 @@ 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
On Wed, Jul 03, 2013 at 11:36:40AM -0700, Kevin Hilman wrote:
The 64-bit requirement can be removed after the conversion of the nsec granularity cputime to work on !64_BIT, which was done in commit 8c23b80e (cputime_nsecs: use math64.h for nsec resolution conversion helpers)
Cc: Frederic Weisbecker fweisbec@gmail.com Signed-off-by: Kevin Hilman khilman@linaro.org
So I finally sat down and checked all the use of cputime_t (I probably missed some) to make sure that readers are safe against concurrent write in 32 bits archs.
And everything looks ok expect perhaps fs/[compat]binfmt_elf*.c that doesn't lock the signal struct before getting tsk->signal->cutime and stuff. But perhaps it's safe for some reason, I'll look more carefully. And I also need to check further itimers code.
But I think I pushed back the ARM support long enough now so it's time to get this patch in. The above issues are mostly details that can be dealt with separately.
Just one thing before we apply this. I haven't checked the arch/* potential unsafe uses of cputime. So it would be nice to bring a new CONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN. This won't require any specific arch support, it would just be there to inform the arch developer, through the help text, about the issue with cputime being u64 and resulting possible race. So the guy can have a look at cputime_t uses in his arch before finally enabling that config.
Also, of course check that arm is fine wrt. that and finally enable it :)
Thanks!
init/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/init/Kconfig b/init/Kconfig index 2d9b831..e151022 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -325,7 +325,7 @@ 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
With the 64-bit requirement removed from virt CPU accounting, allow ARM platforms to enable it.
Cc: Russell King rmk+kernel@arm.linux.org.uk 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 136f263..7850612 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -61,6 +61,7 @@ config ARM select OLD_SIGSUSPEND3 select OLD_SIGACTION select HAVE_CONTEXT_TRACKING + select HAVE_VIRT_CPU_ACCOUNTING help The ARM series is a line of low-power-consumption RISC chip designs licensed by ARM Ltd and targeted at embedded applications and
On Wed, Jul 03, 2013 at 11:36:41AM -0700, Kevin Hilman wrote:
With the 64-bit requirement removed from virt CPU accounting, allow ARM platforms to enable it.
Cc: Russell King rmk+kernel@arm.linux.org.uk 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 136f263..7850612 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -61,6 +61,7 @@ config ARM select OLD_SIGSUSPEND3 select OLD_SIGACTION select HAVE_CONTEXT_TRACKING
- select HAVE_VIRT_CPU_ACCOUNTING
I think you got confused here. HAVE_VIRT_CPU_ACCOUNTING is the arch capability for VIRT_CPU_ACCOUNTING_NATIVE, not for VIRT_CPU_ACCOUNTING_GEN that only requires support for context tracking.
That's my bad, all those names start to be confusing now. The VIRT based Kconfig naming is a bit weird, that doesn't really reflect what the feature is doing. "Virtual cputime accounting" just doesn't give any clue, except perhaps suggesting the stuff deals with virtualization while it actually has nothing to do with. I don't even know what virtual refers to here.
Same goes for vtime based APIs. In fact I just based my work on the legacy that was there and expanded further the non-sense ;-)
I'll need to do a big renaming one day.
But to begin with I should rename s/HAVE_VIRT_CPU_ACCOUNTING/HAVE_VIRT_CPU_ACCOUNTING_NATIVE.
help The ARM series is a line of low-power-consumption RISC chip designs licensed by ARM Ltd and targeted at embedded applications and -- 1.8.3
Frederic Weisbecker fweisbec@gmail.com writes:
On Wed, Jul 03, 2013 at 11:36:41AM -0700, Kevin Hilman wrote:
With the 64-bit requirement removed from virt CPU accounting, allow ARM platforms to enable it.
Cc: Russell King rmk+kernel@arm.linux.org.uk 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 136f263..7850612 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -61,6 +61,7 @@ config ARM select OLD_SIGSUSPEND3 select OLD_SIGACTION select HAVE_CONTEXT_TRACKING
- select HAVE_VIRT_CPU_ACCOUNTING
I think you got confused here. HAVE_VIRT_CPU_ACCOUNTING is the arch capability for VIRT_CPU_ACCOUNTING_NATIVE, not for VIRT_CPU_ACCOUNTING_GEN that only requires support for context tracking.
Yes, I am confused. :/
That's my bad, all those names start to be confusing now. The VIRT based Kconfig naming is a bit weird, that doesn't really reflect what the feature is doing. "Virtual cputime accounting" just doesn't give any clue, except perhaps suggesting the stuff deals with virtualization while it actually has nothing to do with. I don't even know what virtual refers to here.
Same goes for vtime based APIs. In fact I just based my work on the legacy that was there and expanded further the non-sense ;-)
I'll need to do a big renaming one day.
But to begin with I should rename s/HAVE_VIRT_CPU_ACCOUNTING/HAVE_VIRT_CPU_ACCOUNTING_NATIVE.
OK, I just tested and I can indeed drop this patch.
Thanks for clarifying,
Kevin
linaro-kernel@lists.linaro.org
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Frederic Weisbecker -
Kevin Hilman