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Update the vdso timehands only via tc_windup().

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Prior to this change CLOCK_MONOTONIC could go backwards when the timecounter
hardware was changed via 'sysctl kern.timecounter.hardware'. This happened
because the vdso timehands update was missing the special treatment in
tc_windup() when changing timecounters.

Reviewed by:	kib
This commit is contained in:
neel 2015-01-20 03:54:30 +00:00
parent 68d3af83c8
commit 1fe4c6403b
4 changed files with 27 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
sys/kern/kern_tc.c
View File

@ -1424,7 +1424,15 @@ sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
(void)newtc->tc_get_timecount(newtc);
timecounter = newtc;
timekeep_push_vdso();
/*
* The vdso timehands update is deferred until the next
* 'tc_windup()'.
*
* This is prudent given that 'timekeep_push_vdso()' does not
* use any locking and that it can be called in hard interrupt
* context via 'tc_windup()'.
*/
return (0);
}
return (EINVAL);
@ -1982,7 +1990,6 @@ sysctl_fast_gettime(SYSCTL_HANDLER_ARGS)
if (error != 0)
return (error);
vdso_th_enable = old_vdso_th_enable;
timekeep_push_vdso();
return (0);
}
SYSCTL_PROC(_kern_timecounter, OID_AUTO, fast_gettime,
@ -2002,7 +2009,7 @@ tc_fill_vdso_timehands(struct vdso_timehands *vdso_th)
vdso_th->th_counter_mask = th->th_counter->tc_counter_mask;
vdso_th->th_offset = th->th_offset;
vdso_th->th_boottime = boottimebin;
enabled = cpu_fill_vdso_timehands(vdso_th);
enabled = cpu_fill_vdso_timehands(vdso_th, th->th_counter);
if (!vdso_th_enable)
enabled = 0;
return (enabled);
@ -2024,7 +2031,7 @@ tc_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
*(uint64_t *)&vdso_th32->th_offset.frac[0] = th->th_offset.frac;
vdso_th32->th_boottime.sec = boottimebin.sec;
*(uint64_t *)&vdso_th32->th_boottime.frac[0] = boottimebin.frac;
enabled = cpu_fill_vdso_timehands32(vdso_th32);
enabled = cpu_fill_vdso_timehands32(vdso_th32, th->th_counter);
if (!vdso_th_enable)
enabled = 0;
return (enabled);

5
sys/kern/subr_dummy_vdso_tc.c
View File

@ -33,7 +33,7 @@ __FBSDID("$FreeBSD$");
#include <sys/vdso.h>
uint32_t
cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th)
cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th, struct timecounter *tc)
{
return (0);
@ -41,7 +41,8 @@ cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th)
#ifdef COMPAT_FREEBSD32
uint32_t
cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32,
struct timecounter *tc)
{
return (0);

8
sys/sys/vdso.h
View File

@ -69,6 +69,8 @@ int __vdso_gettimekeep(struct vdso_timekeep **tk);
#ifdef _KERNEL
struct timecounter;
void timekeep_push_vdso(void);
uint32_t tc_fill_vdso_timehands(struct vdso_timehands *vdso_th);
@ -81,7 +83,8 @@ uint32_t tc_fill_vdso_timehands(struct vdso_timehands *vdso_th);
* global sysctl enable override is handled by machine-independed code
* after cpu_fill_vdso_timehands() call is made.
*/
uint32_t cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th);
uint32_t cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th,
struct timecounter *tc);
#define VDSO_TH_NUM 4
@ -110,7 +113,8 @@ struct vdso_timekeep32 {
};
uint32_t tc_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32);
uint32_t cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32);
uint32_t cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32,
struct timecounter *tc);
#endif
#endif

13
sys/x86/x86/tsc.c
View File

@ -720,21 +720,22 @@ tsc_get_timecount_low_mfence(struct timecounter *tc)
}
uint32_t
cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th)
cpu_fill_vdso_timehands(struct vdso_timehands *vdso_th, struct timecounter *tc)
{
vdso_th->th_x86_shift = (int)(intptr_t)timecounter->tc_priv;
vdso_th->th_x86_shift = (int)(intptr_t)tc->tc_priv;
bzero(vdso_th->th_res, sizeof(vdso_th->th_res));
return (timecounter == &tsc_timecounter);
return (tc == &tsc_timecounter);
}
#ifdef COMPAT_FREEBSD32
uint32_t
cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32)
cpu_fill_vdso_timehands32(struct vdso_timehands32 *vdso_th32,
struct timecounter *tc)
{
vdso_th32->th_x86_shift = (int)(intptr_t)timecounter->tc_priv;
vdso_th32->th_x86_shift = (int)(intptr_t)tc->tc_priv;
bzero(vdso_th32->th_res, sizeof(vdso_th32->th_res));
return (timecounter == &tsc_timecounter);
return (tc == &tsc_timecounter);
}
#endif