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SubjectRe: PPS parport boot lockup: INFO: HARDIRQ-READ-safe -> HARDIRQ-READ-unsafe lock order detected

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> HOWEVER, even then I think you should see the lockdep message as a
> problem. The automated toolchain is great because it shows problems
> that it thinks might happen - not when they happen, but based on a
> simpler theoretical model. Ignoring the error because there is some
> rule in place that is hard to explain to the automated toolchain is
> the wrong thing to do, because it makes the lockdep automation less
> reliable.

Yeah. Also, inevitably the false positives have a higher likelyhood
of making it into a released kernel, often because the bugs where
there was a real lockup as well got noticed via other means.

It's similar with compiler warnings as well: the questionable ones where
GCC is wrong or at least confused accumulate.

Also note that here there's a real lockup here as well, shortly after the lockdep
message - the boot never continues, the box keep spewing the PPS debug messages:

[ 76.240020] pps pps0: PPS event at 4294911356
[ 76.244380] pps pps0: PPS event at 1295471377.240018362
[ 76.249608] pps pps0: capture assert seq #2
[ 77.252019] pps pps0: PPS event at 4294911609
[ 77.256379] pps pps0: PPS event at 1295471378.252017372
[ 77.261604] pps pps0: capture assert seq #3
[ 78.264021] pps pps0: PPS event at 4294911862
[ 78.268387] pps pps0: PPS event at 1295471379.264018619
[ 78.273621] pps pps0: capture assert seq #4
[ 79.276018] pps pps0: PPS event at 4294912115
[ 79.280384] pps pps0: PPS event at 1295471380.276016791
[ 79.285619] pps pps0: capture assert seq #5

But nothing happens, the boot never continues.

Thanks,

Ingo


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