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SubjectRe: [Fdutils] DMA cache consistency bug introduced in 2.6.28


On Wed, 23 Dec 2009, Andi Kleen wrote:
>
> I suspect it's a system where the APIC timer stops in deeper idle
> states and it supports them. In this case CPU #0 does timer broadcasts
> when needed to wake the other CPUs up from deep C, but for that it has
> to run with HPET. At least the other ones can still enjoy the LAPIC
> timer.

Ahh, ok, that makes sense. I was assuming the broadcast timer would act in
that capacity, but..

> This might suggest that Mark's floppy controller doesn't like
> deep C? Mark, did you try booting with processor.max_cstate=1
> and HPET enabled?

We have indeed had historical issues with floppy and sleep states before.

I do note another issue, though - the floppy driver itself seems totally
broken when it comes to using interleaved sectors. Alain, that "place
logical sectors" code is simply _broken_ - the "while" kicks in only if
the first sector we test is busy _and_ we were at the last sector so that
we increment past F_SECT_PER_TRACK.

So shouldn't that sector layout be something like the appended?

Linus
---
drivers/block/floppy.c | 7 ++-----
1 files changed, 2 insertions(+), 5 deletions(-)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 3266b4f..9c9148c 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -2237,13 +2237,10 @@ static void setup_format_params(int track)
for (count = 1; count <= F_SECT_PER_TRACK; ++count) {
here[n].sect = count;
n = (n + il) % F_SECT_PER_TRACK;
- if (here[n].sect) { /* sector busy, find next free sector */
+ while (here[n].sect) { /* sector busy, find next free sector */
++n;
- if (n >= F_SECT_PER_TRACK) {
+ if (n >= F_SECT_PER_TRACK)
n -= F_SECT_PER_TRACK;
- while (here[n].sect)
- ++n;
- }
}
}
if (_floppy->stretch & FD_SECTBASEMASK) {

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