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sync: Fix logic error from b55bf24858

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That commit adds two hunks, and I _think_ they're backwards.  It adds
code to modify bracket_greater on NegativeTransition triggers, and
bracket_less on PositiveTransition triggers.  That breaks symmetry with
the surrounding code; the code as of this commit could probably be
simplified further.

I can't keep the sync trigger rules in my head for more than about five
minutes at a time, so I'm sending this on for more eyes.  RHEL 6.3's
xserver is shipping with b55bf248 reverted:

    https://bugzilla.redhat.com/show_bug.cgi?id=748704#c33

And there appear to be some upstream reports of the same issue:

    https://bugzilla.gnome.org/show_bug.cgi?id=658955

So I'd like to get this sorted out.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Adam Jackson 2012-07-23 16:34:28 -04:00 committed by Keith Packard
parent 454d0e3a1b
commit 4a6f42dda0
1 changed files with 12 additions and 12 deletions
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24
Xext/sync.c
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@ -1038,15 +1038,15 @@ SyncComputeBracketValues(SyncCounter * pCounter)
pnewltval = &psci->bracket_less; pnewltval = &psci->bracket_less;
} }
else if (XSyncValueEqual(pCounter->value, pTrigger->test_value) && else if (XSyncValueEqual(pCounter->value, pTrigger->test_value) &&
XSyncValueLessThan(pTrigger->test_value, XSyncValueGreaterThan(pTrigger->test_value,
psci->bracket_greater)) { psci->bracket_less)) {
/* /*
* The value is exactly equal to our threshold. We want one * The value is exactly equal to our threshold. We want one
* more event in the positive direction to ensure we pick up * more event in the negative direction to ensure we pick up
* when the value *exceeds* this threshold. * when the value is less than this threshold.
*/ */
psci->bracket_greater = pTrigger->test_value; psci->bracket_less = pTrigger->test_value;
pnewgtval = &psci->bracket_greater; pnewltval = &psci->bracket_less;
} }
} }
else if (pTrigger->test_type == XSyncPositiveTransition && else if (pTrigger->test_type == XSyncPositiveTransition &&
@ -1058,15 +1058,15 @@ SyncComputeBracketValues(SyncCounter * pCounter)
pnewgtval = &psci->bracket_greater; pnewgtval = &psci->bracket_greater;
} }
else if (XSyncValueEqual(pCounter->value, pTrigger->test_value) && else if (XSyncValueEqual(pCounter->value, pTrigger->test_value) &&
XSyncValueGreaterThan(pTrigger->test_value, XSyncValueLessThan(pTrigger->test_value,
psci->bracket_less)) { psci->bracket_greater)) {
/* /*
* The value is exactly equal to our threshold. We want one * The value is exactly equal to our threshold. We want one
* more event in the negative direction to ensure we pick up * more event in the positive direction to ensure we pick up
* when the value is less than this threshold. * when the value *exceeds* this threshold.
*/ */
psci->bracket_less = pTrigger->test_value; psci->bracket_greater = pTrigger->test_value;
pnewltval = &psci->bracket_less; pnewgtval = &psci->bracket_greater;
} }
} }
} /* end for each trigger */ } /* end for each trigger */