Re: long delays (possibly infinite) in time_interpolator_get_counter

From: Christoph Lameter
Date: Fri Jul 29 2005 - 19:40:53 EST

> diff --git a/include/linux/timex.h b/include/linux/timex.h

Oh. Before I forget: You need to make the same changes to the asm code in
arch/ia64/kernel/fsys.S in order for this to work properly. The asm code
has been optimized to the hilt to save every cycle possible. Please dont
add any. The C code is typically bypassed for all user space gettimeofday
/ clock_gettime calls.

Hmm.. However, if you did not see the problem in the asm code (which does
not have the nesting issue of C and wastes some time doing other things)
then we may solve the issue by either also calling asm from kernel space
or making sure that some time is wasted on something else then the
cmpxchg in the inner loop.

Or we can make "nojitter" the default? Then do a

if (nojitter)
printk(KERN_ERR "Beware: SMP system using ITC as a time source!"
"Time may fluctuate.\n");

at bootup and hope for the best?
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