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Commit 5df32107 authored by Prarit Bhargava's avatar Prarit Bhargava Committed by Thomas Gleixner
Browse files

timekeeping: Make fast accessors return 0 before timekeeping is initialized 



printk timestamps will be extended to include mono and boot time by using
the fast timekeeping accessors ktime_get_mono|boot_fast_ns().  The
functions can return garbage before timekeeping is initialized resulting in
garbage timestamps.

Initialize the fast timekeepers with dummy clocks which guarantee a 0
readout up to timekeeping_init().

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1503922914-10660-2-git-send-email-prarit@redhat.com
parent e19b205b

kernel/time/timekeeping.c

+21 −14
Original line number Diff line number Diff line
@@ -60,8 +60,27 @@ struct tk_fast { 
	struct tk_read_base	base[2];

};



static struct tk_fast tk_fast_mono ____cacheline_aligned;

static struct tk_fast tk_fast_raw  ____cacheline_aligned;

/* Suspend-time cycles value for halted fast timekeeper. */

static u64 cycles_at_suspend;



static u64 dummy_clock_read(struct clocksource *cs)

{

	return cycles_at_suspend;

}



static struct clocksource dummy_clock = {

	.read = dummy_clock_read,

};



static struct tk_fast tk_fast_mono ____cacheline_aligned = {

	.base[0] = { .clock = &dummy_clock, },

	.base[1] = { .clock = &dummy_clock, },

};



static struct tk_fast tk_fast_raw  ____cacheline_aligned = {

	.base[0] = { .clock = &dummy_clock, },

	.base[1] = { .clock = &dummy_clock, },

};



/* flag for if timekeeping is suspended */

int __read_mostly timekeeping_suspended;
@@ -477,18 +496,6 @@ u64 notrace ktime_get_boot_fast_ns(void) 
}

EXPORT_SYMBOL_GPL(ktime_get_boot_fast_ns);



/* Suspend-time cycles value for halted fast timekeeper. */

static u64 cycles_at_suspend;



static u64 dummy_clock_read(struct clocksource *cs)

{

	return cycles_at_suspend;

}



static struct clocksource dummy_clock = {

	.read = dummy_clock_read,

};



/**

 * halt_fast_timekeeper - Prevent fast timekeeper from accessing clocksource.

 * @tk: Timekeeper to snapshot.