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Commit 2957abde authored by Mark Salyzyn's avatar Mark Salyzyn Committed by Gagan Malvi
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FROMLIST: [PATCH v5 11/12] lib: vdso: Add support for CLOCK_BOOTTIME 

(cherry pick from url https://patchwork.kernel.org/patch/10044503/

)

Take an effort to recode the arm64 vdso code from assembler to C
previously submitted by Andrew Pinski <apinski@cavium.com>, rework
it for use in both arm and arm64, overlapping any optimizations
for each architecture. But instead of landing it in arm64, land the
result into lib/vdso and unify both implementations to simplify
future maintenance.

Add a case for CLOCK_BOOTTIME as it is popular for measuring
relative time on systems expected to suspend() or hibernate().

Android uses CLOCK_BOOTTIME for all relative time measurements
and timeouts. Switching to vdso reduced CPU utilization and improves
accuracy. There is also a desire by some partners to switch all
logging over to CLOCK_BOOTTIME, and thus this operation alone would
contribute to a near percentile CPU load.

Signed-off-by: default avatarMark Salyzyn <salyzyn@android.com>
Cc: James Morse <james.morse@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Andy Gross <andy.gross@linaro.org>
Cc: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: Andrew Pinski <apinski@cavium.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Bug: 63737556
Bug: 20045882
Change-Id: I76c26b054baf7f1100e03c65d6b16fe649b883b1

Signed-off-by: default avatarstarlight5234 <ifist2834@gmail.com>
Signed-off-by: default avatarTheSync <repo-sync@outlook.com>
parent 5b1770c7

arch/arm/include/asm/vdso_datapage.h

+1 −0
Original line number Diff line number Diff line
@@ -64,6 +64,7 @@ struct vdso_data { 
	u32 tz_minuteswest;	/* timezone info for gettimeofday(2) */

	u32 tz_dsttime;



	u64 btm_nsec;		/* monotonic to boot time */

	/* Raw clocksource multipler */

	u32 cs_raw_mult;

	/* Raw time */

arch/arm/kernel/vdso.c

+1 −0
Original line number Diff line number Diff line
@@ -329,6 +329,7 @@ void update_vsyscall(struct timekeeper *tk) 
		/* tkr_mono.shift == tkr_raw.shift */

		vdso_data->cs_shift		= tk->tkr_mono.shift;

		vdso_data->cs_mask		= tk->tkr_mono.mask;

		vdso_data->btm_nsec		= ktime_to_ns(tk->offs_boot);

	}



	vdso_write_end(vdso_data);

arch/arm64/include/asm/vdso_datapage.h

+1 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ struct vdso_data { 
	__u64 xtime_coarse_nsec;

	__u64 wtm_clock_sec;	/* Wall to monotonic time */

	vdso_wtm_clock_nsec_t wtm_clock_nsec;

	__u64 btm_nsec;		/* monotonic to boot time */

	__u32 tb_seq_count;	/* Timebase sequence counter */

	/* cs_* members must be adjacent and in this order (ldp accesses) */

	__u32 cs_mono_mult;	/* NTP-adjusted clocksource multiplier */

arch/arm64/kernel/vdso.c

+1 −0
Original line number Diff line number Diff line
@@ -268,6 +268,7 @@ void update_vsyscall(struct timekeeper *tk) 
		vdso_data->cs_raw_mult		= tk->tkr_raw.mult;

		/* tkr_mono.shift == tkr_raw.shift */

		vdso_data->cs_shift		= tk->tkr_mono.shift;

		vdso_data->btm_nsec		= ktime_to_ns(tk->offs_boot);

	}



	smp_wmb();

lib/vdso/vgettimeofday.c

+55 −0
Original line number Diff line number Diff line
@@ -247,6 +247,50 @@ static notrace int do_monotonic_raw(const struct vdso_data *vd, 
	return 0;

}



static notrace int do_boottime(const struct vdso_data *vd, struct timespec *ts)

{

	u32 seq, mult, shift;

	u64 nsec, cycle_last, wtm_nsec;

#ifdef ARCH_CLOCK_FIXED_MASK

	static const u64 mask = ARCH_CLOCK_FIXED_MASK;

#else

	u64 mask;

#endif

	__kernel_time_t sec;



	do {

		seq = vdso_read_begin(vd);



		if (vd->use_syscall)

			return -1;



		cycle_last = vd->cs_cycle_last;



		mult = vd->cs_mono_mult;

		shift = vd->cs_shift;

#ifndef ARCH_CLOCK_FIXED_MASK

		mask = vd->cs_mask;

#endif



		sec = vd->xtime_clock_sec;

		nsec = vd->xtime_clock_snsec;



		sec += vd->wtm_clock_sec;

		wtm_nsec = vd->wtm_clock_nsec + vd->btm_nsec;



	} while (unlikely(vdso_read_retry(vd, seq)));



	nsec += get_clock_shifted_nsec(cycle_last, mult, mask);

	nsec >>= shift;

	nsec += wtm_nsec;



	/* open coding timespec_add_ns to save a ts->tv_nsec = 0 */

	ts->tv_sec = sec + __iter_div_u64_rem(nsec, NSEC_PER_SEC, &nsec);

	ts->tv_nsec = nsec;



	return 0;

}



#else /* ARCH_PROVIDES_TIMER */



static notrace int do_realtime(const struct vdso_data *vd, struct timespec *ts)
@@ -265,6 +309,12 @@ static notrace int do_monotonic_raw(const struct vdso_data *vd, 
	return -1;

}



static notrace int do_boottime(const struct vdso_data *vd,

			       struct timespec *ts)

{

	return -1;

}



#endif /* ARCH_PROVIDES_TIMER */



notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
@@ -290,6 +340,10 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts) 
		if (do_monotonic_raw(vd, ts))

			goto fallback;

		break;

	case CLOCK_BOOTTIME:

		if (do_boottime(vd, ts))

			goto fallback;

		break;

	default:

		goto fallback;

	}
@@ -326,6 +380,7 @@ int __vdso_clock_getres(clockid_t clock, struct timespec *res) 
	long nsec;



	if (clock == CLOCK_REALTIME ||

	    clock == CLOCK_BOOTTIME ||

	    clock == CLOCK_MONOTONIC ||

	    clock == CLOCK_MONOTONIC_RAW)

		nsec = MONOTONIC_RES_NSEC;