linux-kernel - [PATCH] ppc64: select HAVE_CONTEXT

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Message-Id: <1449701034-5444-1-git-send-email-yang.shi@linaro.org>
Date:	Wed,  9 Dec 2015 14:43:54 -0800
From:	Yang Shi <yang.shi@...aro.org>
To:	benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linaro-kernel@...ts.linaro.org, yang.shi@...aro.org
Subject: [PATCH] ppc64: select HAVE_CONTEXT_TRACKING by default

The functionality of context tracking has been implemented by PPC64 and
HAVE_CONTEXT_TRACKING was selected by pseries by default.
Actually, it is applicale to all PPC64 platforms, so select it in PPC64
generic Kconfig.

NO_HZ_FULL depends on it, with this change NO_HZ_FULL could be enabled
for all PPC64 machines.

Signed-off-by: Yang Shi <yang.shi@...aro.org>
---
Following the instruction in Documentation/timers/NO_HZ.txt, I tested full nohz
on my FSL T2080 target, the below trace log shows it works well.

       user_loop-574   [001] d..1   137.044892: tick_stop: success=yes msg=
       user_loop-574   [001] d.h1   138.044880: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=137796002092
       user_loop-574   [001] d.h1   139.044880: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=138796002129
       user_loop-574   [001] d.h1   140.044880: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=139796002219
       user_loop-574   [001] d.h1   141.044880: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=140796002229
       user_loop-574   [001] d.h1   142.044879: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=141796002159
       user_loop-574   [001] d.h1   143.044879: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=142796002142
       user_loop-574   [001] d.h1   144.044878: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=143796002046
       user_loop-574   [001] d.h1   145.044878: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=144796002189
       user_loop-574   [001] d.h1   146.044878: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=145796002199
       user_loop-574   [001] d.h1   147.044880: hrtimer_expire_entry: hrtimer=c00000007fd22d10 function=.tick_sched_timer now=146796003836

It shows the timer tick just comes in every second.

It should be low risk to have problem on other PPC64 targets, although they are
not tested. 

 arch/powerpc/platforms/Kconfig.cputype | 1 +
 arch/powerpc/platforms/pseries/Kconfig | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
index 142dff5..7b25dd1 100644
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -3,6 +3,7 @@ config PPC64
 	default n
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select ZLIB_DEFLATE
+	select HAVE_CONTEXT_TRACKING
 	help
 	  This option selects whether a 32-bit or a 64-bit kernel
 	  will be built.
diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index bec90fb..6853148 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -17,7 +17,6 @@ config PPC_PSERIES
 	select PPC_UDBG_16550
 	select PPC_NATIVE
 	select PPC_DOORBELL
-	select HAVE_CONTEXT_TRACKING
 	select HOTPLUG_CPU if SMP
 	select ARCH_RANDOM
 	select PPC_DOORBELL
-- 
2.0.2

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