Differential D7473 Diff 19397 head/lib/libc/sys/__vdso_gettimeofday.c

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head/lib/libc/sys/__vdso_gettimeofday.c

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	#include <sys/elf.h>			#include <sys/elf.h>
	#include <sys/time.h>			#include <sys/time.h>
	#include <sys/vdso.h>			#include <sys/vdso.h>
	#include <errno.h>			#include <errno.h>
	#include <time.h>			#include <time.h>
	#include <machine/atomic.h>			#include <machine/atomic.h>
	#include "libc_private.h"			#include "libc_private.h"

	static u_int			static int
	tc_delta(const struct vdso_timehands *th)			tc_delta(const struct vdso_timehands th, u_int delta)
	{			{
				int error;
				u_int tc;

	return ((__vdso_gettc(th) - th->th_offset_count) &			error = __vdso_gettc(th, &tc);
	th->th_counter_mask);			if (error == 0)
				*delta = (tc - th->th_offset_count) & th->th_counter_mask;
				return (error);
	}			}

	/*			/*
	* Calculate the absolute or boot-relative time from the			* Calculate the absolute or boot-relative time from the
	* machine-specific fast timecounter and the published timehands			* machine-specific fast timecounter and the published timehands
	* structure read from the shared page.			* structure read from the shared page.
	*			*
	* The lockless reading scheme is similar to the one used to read the			* The lockless reading scheme is similar to the one used to read the
	* in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code			* in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
	* is based on the kernel implementation.			* is based on the kernel implementation.
	*/			*/
	static int			static int
	binuptime(struct bintime bt, struct vdso_timekeep tk, int abs)			binuptime(struct bintime bt, struct vdso_timekeep tk, int abs)
	{			{
	struct vdso_timehands *th;			struct vdso_timehands *th;
	uint32_t curr, gen;			uint32_t curr, gen;
				u_int delta;
				int error;

	do {			do {
	if (!tk->tk_enabled)			if (!tk->tk_enabled)
	return (ENOSYS);			return (ENOSYS);

	curr = atomic_load_acq_32(&tk->tk_current);			curr = atomic_load_acq_32(&tk->tk_current);
	th = &tk->tk_th[curr];			th = &tk->tk_th[curr];
	if (th->th_algo != VDSO_TH_ALGO_1)
	return (ENOSYS);
	gen = atomic_load_acq_32(&th->th_gen);			gen = atomic_load_acq_32(&th->th_gen);
	*bt = th->th_offset;			*bt = th->th_offset;
	bintime_addx(bt, th->th_scale * tc_delta(th));			error = tc_delta(th, &delta);
				if (error == EAGAIN)
				continue;
				if (error != 0)
				return (error);
				bintime_addx(bt, th->th_scale * delta);
	if (abs)			if (abs)
	bintime_add(bt, &th->th_boottime);			bintime_add(bt, &th->th_boottime);

	/*			/*
	* Ensure that the load of th_offset is completed			* Ensure that the load of th_offset is completed
	* before the load of th_gen.			* before the load of th_gen.
	*/			*/
	atomic_thread_fence_acq();			atomic_thread_fence_acq();
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