Re: [PATCH_TAKE_2] now < last_tick problem

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2003-10-11 02:42:35
Ian,

Just a quick note (got to run): I think you correctly identified the
race causing the now < last_tick problem.  Purely from (bad) memory, I
think the problem was introduced when xtime_lock was converted from an
irq-safe spinlock to a seq-lock.  In theory, xtime_lock still protects
get_offset(), but the theory only holds as long as the seq-lock body
is "transactional" (no side-effects until read_seqretry() returns 0).
I think the source of the probem is that we consider the value
returned by get_offset() to be valid EVEN when read_seqretry() returns
1.  Because of that, we'll end up updating last_nsec_offset with a
potentialy bad value.

	--david
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Received on Fri Oct 10 12:53:53 2003

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