Re: [Xenomai-core] [BUG] pit clocksource broken under Xenomai

[Jan Kiszka <jan.kiszka@domain.hid>]

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Jan Kiszka wrote:
> Hi,
> 
> just checked on real hardware (found in qemu originally):
> 
> When Linux uses the pit clocksource AND Xenomai is attached, the system
> time no longer makes progress. Observed under 2.6.20 with 1.7-03 and
> newer patches, Xenomai trunk.
> 
> I guess not many people will be affected by this and I'm lacking time to
> debug, so I'm just dumping the report and running away...

Somehow I hate open issues...

I recalled some private thread with you, Philippe, about this particular
line in pid_read(). A look at it again revealed the reason for this bug.

Jan

PS: pending_patches++ ;)


---
 arch/i386/kernel/i8253.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6.20/arch/i386/kernel/i8253.c
===================================================================
--- linux-2.6.20.orig/arch/i386/kernel/i8253.c
+++ linux-2.6.20/arch/i386/kernel/i8253.c
@@ -47,7 +47,8 @@ static cycle_t pit_read(void)
 
 #ifdef CONFIG_IPIPE
 	if (!__ipipe_pipeline_head_p(ipipe_root_domain))
-		return 0;	/* We don't really own the PIT. */
+		/* We don't own the PIT, fall back to jiffies. */
+		return (cycle_t)(jiffies * LATCH);
 #endif /* CONFIG_IPIPE */
 
 	spin_lock_irqsave(&i8253_lock, flags);



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