Commit a56c41e5 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'timers-urgent-2020-01-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull timer fixes from Thomas Gleixner:
 "Two fixes for the generic VDSO code which missed 5.5:

   - Make the update to the coarse timekeeper unconditional.

     This is required because the coarse timekeeper interfaces in the
     VDSO do not depend on a VDSO capable clocksource. If the system
     does not have a VDSO capable clocksource and the update is
     depending on the VDSO capable clocksource, the coarse VDSO
     interfaces would operate on stale data forever.

   - Invert the logic of __arch_update_vdso_data() to avoid further head
     scratching.

     Tripped over this several times while analyzing the update problem
     above"

* tag 'timers-urgent-2020-01-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lib/vdso: Update coarse timekeeper unconditionally
  lib/vdso: Make __arch_update_vdso_data() logic understandable
parents b1dba247 9f24c540

arch/arm/include/asm/vdso/vsyscall.h

+2 −2
Original line number Diff line number Diff line
@@ -34,9 +34,9 @@ struct vdso_data *__arm_get_k_vdso_data(void) 
#define __arch_get_k_vdso_data __arm_get_k_vdso_data



static __always_inline

int __arm_update_vdso_data(void)

bool __arm_update_vdso_data(void)

{

	return !cntvct_ok;

	return cntvct_ok;

}

#define __arch_update_vdso_data __arm_update_vdso_data

include/asm-generic/vdso/vsyscall.h

+2 −2
Original line number Diff line number Diff line
@@ -12,9 +12,9 @@ static __always_inline struct vdso_data *__arch_get_k_vdso_data(void) 
#endif /* __arch_get_k_vdso_data */



#ifndef __arch_update_vdso_data

static __always_inline int __arch_update_vdso_data(void)

static __always_inline bool __arch_update_vdso_data(void)

{

	return 0;

	return true;

}

#endif /* __arch_update_vdso_data */

kernel/time/vsyscall.c

+17 −20
Original line number Diff line number Diff line
@@ -28,11 +28,6 @@ static inline void update_vdso_data(struct vdso_data *vdata, 
	vdata[CS_RAW].mult			= tk->tkr_raw.mult;

	vdata[CS_RAW].shift			= tk->tkr_raw.shift;



	/* CLOCK_REALTIME */

	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];

	vdso_ts->sec	= tk->xtime_sec;

	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;



	/* CLOCK_MONOTONIC */

	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_MONOTONIC];

	vdso_ts->sec	= tk->xtime_sec + tk->wall_to_monotonic.tv_sec;
@@ -70,12 +65,6 @@ static inline void update_vdso_data(struct vdso_data *vdata, 
	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_TAI];

	vdso_ts->sec	= tk->xtime_sec + (s64)tk->tai_offset;

	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;



	/*

	 * Read without the seqlock held by clock_getres().

	 * Note: No need to have a second copy.

	 */

	WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);

}



void update_vsyscall(struct timekeeper *tk)
@@ -84,20 +73,17 @@ void update_vsyscall(struct timekeeper *tk) 
	struct vdso_timestamp *vdso_ts;

	u64 nsec;



	if (__arch_update_vdso_data()) {

		/*

		 * Some architectures might want to skip the update of the

		 * data page.

		 */

		return;

	}



	/* copy vsyscall data */

	vdso_write_begin(vdata);



	vdata[CS_HRES_COARSE].clock_mode	= __arch_get_clock_mode(tk);

	vdata[CS_RAW].clock_mode		= __arch_get_clock_mode(tk);



	/* CLOCK_REALTIME also required for time() */

	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME];

	vdso_ts->sec	= tk->xtime_sec;

	vdso_ts->nsec	= tk->tkr_mono.xtime_nsec;



	/* CLOCK_REALTIME_COARSE */

	vdso_ts		= &vdata[CS_HRES_COARSE].basetime[CLOCK_REALTIME_COARSE];

	vdso_ts->sec	= tk->xtime_sec;
@@ -110,6 +96,17 @@ void update_vsyscall(struct timekeeper *tk) 
	nsec		= nsec + tk->wall_to_monotonic.tv_nsec;

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



	/*

	 * Read without the seqlock held by clock_getres().

	 * Note: No need to have a second copy.

	 */

	WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);



	/*

	 * Architectures can opt out of updating the high resolution part

	 * of the VDSO.

	 */

	if (__arch_update_vdso_data())

		update_vdso_data(vdata, tk);



	__arch_update_vsyscall(vdata, tk);

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