* x86, vmi: TSC going backwards check in vmi clocksource
@ 2009-02-18 20:33 Alok Kataria
2009-02-19 11:18 ` Ingo Molnar
2009-02-20 17:58 ` Ingo Molnar
0 siblings, 2 replies; 7+ messages in thread
From: Alok Kataria @ 2009-02-18 20:33 UTC (permalink / raw)
To: Ingo Molnar, the arch/x86 maintainers; +Cc: LKML, Zachary Amsden
From: Alok N Kataria <akataria@vmware.com>
Similar to the check for TSC going backwards in the TSC clocksource, we also
need this check for VMI clocksource.
Signed-off-by: Alok N Kataria <akataria@vmware.com>
Cc: stable@kernel.org
---
arch/x86/kernel/vmiclock_32.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/vmiclock_32.c b/arch/x86/kernel/vmiclock_32.c
index c4c1f9e..bde106c 100644
--- a/arch/x86/kernel/vmiclock_32.c
+++ b/arch/x86/kernel/vmiclock_32.c
@@ -283,10 +283,13 @@ void __devinit vmi_time_ap_init(void)
#endif
/** vmi clocksource */
+static struct clocksource clocksource_vmi;
static cycle_t read_real_cycles(void)
{
- return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
+ cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
+ return ret >= clocksource_vmi.cycle_last ?
+ ret : clocksource_vmi.cycle_last;
}
static struct clocksource clocksource_vmi = {
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: x86, vmi: TSC going backwards check in vmi clocksource
2009-02-18 20:33 x86, vmi: TSC going backwards check in vmi clocksource Alok Kataria
@ 2009-02-19 11:18 ` Ingo Molnar
2009-02-19 18:03 ` Alok Kataria
2009-02-20 17:58 ` Ingo Molnar
1 sibling, 1 reply; 7+ messages in thread
From: Ingo Molnar @ 2009-02-19 11:18 UTC (permalink / raw)
To: Alok Kataria; +Cc: the arch/x86 maintainers, LKML, Zachary Amsden
* Alok Kataria <akataria@vmware.com> wrote:
> From: Alok N Kataria <akataria@vmware.com>
>
> Similar to the check for TSC going backwards in the TSC
> clocksource, we also need this check for VMI clocksource.
ok. Precisely what kind of bug/symptoms does this fix?
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: x86, vmi: TSC going backwards check in vmi clocksource
2009-02-19 11:18 ` Ingo Molnar
@ 2009-02-19 18:03 ` Alok Kataria
2009-02-19 18:11 ` Ingo Molnar
0 siblings, 1 reply; 7+ messages in thread
From: Alok Kataria @ 2009-02-19 18:03 UTC (permalink / raw)
To: Ingo Molnar; +Cc: the arch/x86 maintainers, LKML, Zach Amsden
On Thu, 2009-02-19 at 03:18 -0800, Ingo Molnar wrote:
> * Alok Kataria <akataria@vmware.com> wrote:
>
> > From: Alok N Kataria <akataria@vmware.com>
> >
> > Similar to the check for TSC going backwards in the TSC
> > clocksource, we also need this check for VMI clocksource.
>
> ok. Precisely what kind of bug/symptoms does this fix?
If the read CYCLES_REAL counter value is less than the cycle_last value,
it may result in time jumps.
I also saw some messages about process being stuck for more than
120sec, which was traced back to this.
Thanks,
Alok
>
> Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: x86, vmi: TSC going backwards check in vmi clocksource
2009-02-19 18:03 ` Alok Kataria
@ 2009-02-19 18:11 ` Ingo Molnar
0 siblings, 0 replies; 7+ messages in thread
From: Ingo Molnar @ 2009-02-19 18:11 UTC (permalink / raw)
To: Alok Kataria; +Cc: the arch/x86 maintainers, LKML, Zach Amsden
* Alok Kataria <akataria@vmware.com> wrote:
> On Thu, 2009-02-19 at 03:18 -0800, Ingo Molnar wrote:
> > * Alok Kataria <akataria@vmware.com> wrote:
> >
> > > From: Alok N Kataria <akataria@vmware.com>
> > >
> > > Similar to the check for TSC going backwards in the TSC
> > > clocksource, we also need this check for VMI clocksource.
> >
> > ok. Precisely what kind of bug/symptoms does this fix?
>
> If the read CYCLES_REAL counter value is less than the cycle_last value,
> it may result in time jumps.
> I also saw some messages about process being stuck for more than
> 120sec, which was traced back to this.
Applied to tip:x86/urgent, thanks Alok!
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: x86, vmi: TSC going backwards check in vmi clocksource
2009-02-18 20:33 x86, vmi: TSC going backwards check in vmi clocksource Alok Kataria
2009-02-19 11:18 ` Ingo Molnar
@ 2009-02-20 17:58 ` Ingo Molnar
2009-02-20 18:23 ` Alok Kataria
1 sibling, 1 reply; 7+ messages in thread
From: Ingo Molnar @ 2009-02-20 17:58 UTC (permalink / raw)
To: Alok Kataria
Cc: the arch/x86 maintainers, LKML, Zachary Amsden, Andrew Morton
* Alok Kataria <akataria@vmware.com> wrote:
> static cycle_t read_real_cycles(void)
> {
> - return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
> + cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
> + return ret >= clocksource_vmi.cycle_last ?
> + ret : clocksource_vmi.cycle_last;
btw., could you please clean this up to use max()?
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: x86, vmi: TSC going backwards check in vmi clocksource
2009-02-20 17:58 ` Ingo Molnar
@ 2009-02-20 18:23 ` Alok Kataria
2009-02-20 18:31 ` Ingo Molnar
0 siblings, 1 reply; 7+ messages in thread
From: Alok Kataria @ 2009-02-20 18:23 UTC (permalink / raw)
To: Ingo Molnar; +Cc: the arch/x86 maintainers, LKML, Zach Amsden, Andrew Morton
On Fri, 2009-02-20 at 09:58 -0800, Ingo Molnar wrote:
> * Alok Kataria <akataria@vmware.com> wrote:
>
> > static cycle_t read_real_cycles(void)
> > {
> > - return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
> > + cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
> > + return ret >= clocksource_vmi.cycle_last ?
> > + ret : clocksource_vmi.cycle_last;
>
> btw., could you please clean this up to use max()?
Please find it below, on top of current tip/master.
--
cleanup vmi_read_cycles to use max()
Signed-off-by: Alok N Kataria <akataria@vmware.com>
---
arch/x86/kernel/vmiclock_32.c | 3 +--
1 files changed, 1 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/vmiclock_32.c b/arch/x86/kernel/vmiclock_32.c
index 9cd28c0..b77ad57 100644
--- a/arch/x86/kernel/vmiclock_32.c
+++ b/arch/x86/kernel/vmiclock_32.c
@@ -288,8 +288,7 @@ static struct clocksource clocksource_vmi;
static cycle_t read_real_cycles(void)
{
cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
- return ret >= clocksource_vmi.cycle_last ?
- ret : clocksource_vmi.cycle_last;
+ return max(ret, clocksource_vmi.cycle_last);
}
static struct clocksource clocksource_vmi = {
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: x86, vmi: TSC going backwards check in vmi clocksource
2009-02-20 18:23 ` Alok Kataria
@ 2009-02-20 18:31 ` Ingo Molnar
0 siblings, 0 replies; 7+ messages in thread
From: Ingo Molnar @ 2009-02-20 18:31 UTC (permalink / raw)
To: Alok Kataria; +Cc: the arch/x86 maintainers, LKML, Zach Amsden, Andrew Morton
* Alok Kataria <akataria@vmware.com> wrote:
> On Fri, 2009-02-20 at 09:58 -0800, Ingo Molnar wrote:
> > * Alok Kataria <akataria@vmware.com> wrote:
> >
> > > static cycle_t read_real_cycles(void)
> > > {
> > > - return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
> > > + cycle_t ret = (cycle_t)vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
> > > + return ret >= clocksource_vmi.cycle_last ?
> > > + ret : clocksource_vmi.cycle_last;
> >
> > btw., could you please clean this up to use max()?
>
> Please find it below, on top of current tip/master.
Applied to tip:x86/cleanups, thanks!
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2009-02-20 18:32 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
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2009-02-18 20:33 x86, vmi: TSC going backwards check in vmi clocksource Alok Kataria
2009-02-19 11:18 ` Ingo Molnar
2009-02-19 18:03 ` Alok Kataria
2009-02-19 18:11 ` Ingo Molnar
2009-02-20 17:58 ` Ingo Molnar
2009-02-20 18:23 ` Alok Kataria
2009-02-20 18:31 ` Ingo Molnar
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