Re: [ros-dev] [ros-diffs] [tkreuzer] 53496: [HAL] We cannot make any assumptions about the latency whith which the timer interrupt fires after a rollover, since VBox (other VMs probably as well) doesn't always meet this. Ad...

[Alex Ionescu]

Funny how Windows works without these hacks.

Let's hide more bugs :D

Best regards,
Alex Ionescu

On Tue, Aug 30, 2011 at 12:01 PM, [e-mail] wrote:
> Author: tkreuzer
> Date: Tue Aug 30 12:01:01 2011
> New Revision: 53496
>
> URL: http://svn.reactos.org/svn/reactos?rev=53496&view=rev
> Log:
> [HAL]
> We cannot make any assumptions about the latency whith which the timer
> interrupt fires after a rollover, since VBox (other VMs probably as well)
> doesn't always meet this. Add another check to KeQueryPerformanceCounter
> that gracefully handles missing interrupts. Also raise to DISPATCH_LEVEL,
> since the function is not reentrant.
>
> Modified:
>    trunk/reactos/hal/halx86/generic/timer.c
>
> Modified: trunk/reactos/hal/halx86/generic/timer.c
> URL:
> http://svn.reactos.org/svn/reactos/trunk/reactos/hal/halx86/generic/timer.c?...
>
> ==============================================================================
> --- trunk/reactos/hal/halx86/generic/timer.c [iso-8859-1] (original)
> +++ trunk/reactos/hal/halx86/generic/timer.c [iso-8859-1] Tue Aug 30
> 12:01:01 2011
> @@ -253,6 +253,7 @@
>  {
>     LARGE_INTEGER CurrentPerfCounter;
>     ULONG CounterValue, ClockDelta;
>
> KIRQL OldIrql;
>
> /* If caller wants performance frequency, return hardcoded value */
> if (PerformanceFrequency) PerformanceFrequency->QuadPart =
>
> PIT_FREQUENCY;
> @@ -262,6 +263,10 @@
> /* Check if interrupts are disabled */
> if(!(__readeflags() & EFLAGS_INTERRUPT_MASK)) return HalpPerfCounter;
>
> /* Raise irql to DISPATCH_LEVEL */
>
> OldIrql = KeGetCurrentIrql();
>
> if (OldIrql < DISPATCH_LEVEL) KfRaiseIrql(DISPATCH_LEVEL);
>
> do
> {
>
> @@ -287,13 +292,21 @@
>     /* Add the clock delta */
>     CurrentPerfCounter.QuadPart += ClockDelta;
> /* This must be true unless HalpPerfCounter has changed sign,
>   which takes approximately 245,118 years */
> ASSERT(CurrentPerfCounter.QuadPart >= HalpLastPerfCounter.QuadPart);
>
> /* Check if the value is smaller then before, this means, we somehow
>   missed an interrupt. This is a sign that the timer interrupt
>   is very inaccurate. Probably a virtual machine. */
>
> if (CurrentPerfCounter.QuadPart < HalpLastPerfCounter.QuadPart)
>
> {
>    /* We missed an interrupt. Assume we will receive it later */
>    CurrentPerfCounter.QuadPart += HalpCurrentRollOver;
>
> }
>
> /* Update the last counter value */
> HalpLastPerfCounter = CurrentPerfCounter;
>
> /* Restore previous irql */
>
> if (OldIrql < DISPATCH_LEVEL) KfLowerIrql(OldIrql);
>
> /* Return the result */
>   return CurrentPerfCounter;
>
> }