Commit b4f711ee authored by John Stultz's avatar John Stultz Committed by Thomas Gleixner
Browse files

time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitons 



Kay Sievers noted that the ALWAYS_USE_PERSISTENT_CLOCK config,
which enables some minor compile time optimization to avoid
uncessary code in mostly the suspend/resume path could cause
problems for userland.

In particular, the dependency for RTC_HCTOSYS on
!ALWAYS_USE_PERSISTENT_CLOCK, which avoids setting the time
twice and simplifies suspend/resume, has the side effect
of causing the /sys/class/rtc/rtcN/hctosys flag to always be
zero, and this flag is commonly used by udev to setup the
/dev/rtc symlink to /dev/rtcN, which can cause pain for
older applications.

While the udev rules could use some work to be less fragile,
breaking userland should strongly be avoided. Additionally
the compile time optimizations are fairly minor, and the code
being optimized is likely to be reworked in the future, so
lets revert this change.

Reported-by: default avatarKay Sievers <kay@vrfy.org>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Cc: stable <stable@vger.kernel.org> #3.9
Cc: Feng Tang <feng.tang@intel.com>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Link: http://lkml.kernel.org/r/1366828376-18124-1-git-send-email-john.stultz@linaro.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 42a5cf46

arch/x86/Kconfig

+0 −1
Original line number Original line Diff line number Diff line
@@ -108,7 +108,6 @@ config X86 
	select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)

	select GENERIC_CLOCKEVENTS_BROADCAST if X86_64 || (X86_32 && X86_LOCAL_APIC)

	select GENERIC_TIME_VSYSCALL if X86_64

	select GENERIC_TIME_VSYSCALL if X86_64

	select KTIME_SCALAR if X86_32

	select KTIME_SCALAR if X86_32

	select ALWAYS_USE_PERSISTENT_CLOCK

	select GENERIC_STRNCPY_FROM_USER

	select GENERIC_STRNCPY_FROM_USER

	select GENERIC_STRNLEN_USER

	select GENERIC_STRNLEN_USER

	select HAVE_CONTEXT_TRACKING if X86_64

	select HAVE_CONTEXT_TRACKING if X86_64

drivers/rtc/Kconfig

+0 −2
Original line number Original line Diff line number Diff line
@@ -20,7 +20,6 @@ if RTC_CLASS 
config RTC_HCTOSYS

config RTC_HCTOSYS

	bool "Set system time from RTC on startup and resume"

	bool "Set system time from RTC on startup and resume"

	default y

	default y

	depends on !ALWAYS_USE_PERSISTENT_CLOCK

	help

	help

	  If you say yes here, the system time (wall clock) will be set using

	  If you say yes here, the system time (wall clock) will be set using

	  the value read from a specified RTC device. This is useful to avoid

	  the value read from a specified RTC device. This is useful to avoid
@@ -29,7 +28,6 @@ config RTC_HCTOSYS 
config RTC_SYSTOHC

config RTC_SYSTOHC

	bool "Set the RTC time based on NTP synchronization"

	bool "Set the RTC time based on NTP synchronization"

	default y

	default y

	depends on !ALWAYS_USE_PERSISTENT_CLOCK

	help

	help

	  If you say yes here, the system time (wall clock) will be stored

	  If you say yes here, the system time (wall clock) will be stored

	  in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11

	  in the RTC specified by RTC_HCTOSYS_DEVICE approximately every 11

include/linux/time.h

+0 −4
Original line number Original line Diff line number Diff line
@@ -117,14 +117,10 @@ static inline bool timespec_valid_strict(const struct timespec *ts) 




extern bool persistent_clock_exist;

extern bool persistent_clock_exist;





#ifdef ALWAYS_USE_PERSISTENT_CLOCK

#define has_persistent_clock()	true

#else

static inline bool has_persistent_clock(void)

static inline bool has_persistent_clock(void)

{

{

	return persistent_clock_exist;

	return persistent_clock_exist;

}

}

#endif





extern void read_persistent_clock(struct timespec *ts);

extern void read_persistent_clock(struct timespec *ts);

extern void read_boot_clock(struct timespec *ts);

extern void read_boot_clock(struct timespec *ts);

kernel/time/Kconfig

+0 −5
Original line number Original line Diff line number Diff line
@@ -12,11 +12,6 @@ config CLOCKSOURCE_WATCHDOG 
config ARCH_CLOCKSOURCE_DATA

config ARCH_CLOCKSOURCE_DATA

	bool

	bool





# Platforms has a persistent clock

config ALWAYS_USE_PERSISTENT_CLOCK

	bool

	default n



# Timekeeping vsyscall support

# Timekeeping vsyscall support

config GENERIC_TIME_VSYSCALL

config GENERIC_TIME_VSYSCALL

	bool

	bool

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