nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config

Turn the full dynticks passive dependency on VIRT_CPU_ACCOUNTING_GEN
to an active one.

The full dynticks Kconfig is currently hidden behind the full dynticks
cputime accounting, which is an awkward and counter-intuitive layout:
the user first has to select the dynticks cputime accounting in order
to make the full dynticks feature to be visible.

We definetly want it the other way around. The usual way to perform
this kind of active dependency is use "select" on the depended target.
Now we can't use the Kconfig "select" instruction when the target is
a "choice".

So this patch inspires on how the RCU subsystem Kconfig interact
with its dependencies on SMP and PREEMPT: we make sure that cputime
accounting can't propose another option than VIRT_CPU_ACCOUNTING_GEN
when NO_HZ_FULL is selected by using the right "depends on" instruction
for each cputime accounting choices.

v2: Keep full dynticks cputime accounting available even without
full dynticks, as per Paul McKenney's suggestion.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

diff --git a/init/Kconfig b/init/Kconfig
index edc8132584f1530070d4d0798999873ebf79a90b..8f97a7407714736cf6507c1d6f897f3303f12e6f 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -306,7 +306,7 @@ choice
 # Kind of a stub config for the pure tick based cputime accounting
 config TICK_CPU_ACCOUNTING
        bool "Simple tick based cputime accounting"
-       depends on !S390
+       depends on !S390 && !NO_HZ_FULL
        help
          This is the basic tick based cputime accounting that maintains
          statistics about user, system and idle time spent on per jiffies
@@ -316,7 +316,7 @@ config TICK_CPU_ACCOUNTING
 
 config VIRT_CPU_ACCOUNTING_NATIVE
        bool "Deterministic task and CPU time accounting"
-       depends on HAVE_VIRT_CPU_ACCOUNTING
+       depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
        select VIRT_CPU_ACCOUNTING
        help
          Select this option to enable more accurate task and CPU time
@@ -346,7 +346,7 @@ config VIRT_CPU_ACCOUNTING_GEN
 
 config IRQ_TIME_ACCOUNTING
        bool "Fine granularity task level IRQ time accounting"
-       depends on HAVE_IRQ_TIME_ACCOUNTING
+       depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
        help
          Select this option to enable fine granularity task irq time
          accounting. This is done by reading a timestamp on each

diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 1ea2bba4a68646059b5f3e4a3358bf5139192e91..a2ddd650cb92f98a50b3ba1fb9befd3ff07e3b6d 100644 (file)
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -104,11 +104,13 @@ config NO_HZ_FULL
        depends on SMP
        # RCU_USER_QS dependency
        depends on HAVE_CONTEXT_TRACKING
-       depends on VIRT_CPU_ACCOUNTING_GEN
+       # VIRT_CPU_ACCOUNTING_GEN dependency
+       depends on 64BIT
        select NO_HZ_COMMON
        select RCU_USER_QS
        select RCU_NOCB_CPU
        select RCU_NOCB_CPU_ALL
+       select VIRT_CPU_ACCOUNTING_GEN
        select CONTEXT_TRACKING_FORCE
        select IRQ_WORK
        help