[yocto] nativesdk-libgcc-initial race condition and sstate-mirror problems

[Dimitar Yordanov]

Hi all,

we are experiencing problems with our sstate-mirror handling after
applying commit: be02588097dcdb61b76e5788a67ab062dabc78ad

Here is a short explanation to what we do and what happens:

We have an sstate-mirror, which we want to keep up to date when new
builds are executed and also be clean from unused sstate files. For
this purpose we set the SSTATE_MIRROR variable to point to the latest
stable cache we have. Then we trigger a new build with changes to some
of the recipes/sources. Under SSTATE_DIR a new cache is being created
which has links to SSTATE_MIRROR for caches, which are still valid.

To get a new clean SSTATE_MIRROR we take the newly created SSTATE_DIR
and replace all the links with the real files. Then we promote that
SSTATE_DIR to be the new SSTATE_MIRROR.

Where does the problem arises ...

With the previously mentioned patch the do_package tasks are being
skipped, thus there are no entries or links for that in the new
SSTATE_DIR. When we now promote the SSTATE_DIR to a SSTATE_MIRROR
bitbake decides that the do_package tasks need to be rebuilt, because
the squashed reverse dependencies are not covered
(runqueue.py:1931->execute). setscene_depvalid does not even get
called.

Maybe we wouldn't have noticed that, but we get some wired race
conditions because of that, between nativesdk-libgcc-initial,
nativesdk-glibc and nativesdk-linux-libc-headers. What happens:

All packages have an sstate cache entries (apart from do_package), and
they get executed, which populates the nativesdk sysroot with limits.h
and linux/limits.h

And now bitbake decides it should re-trigger the do_configure stage of
nativesdk-linux-libc-headers. That removes linux/limits.h, but
limits.h is still there and includes (indirect) linux/limits.h. In
this moment the do_configure step from nativesdk-libgcc-initial is
called, which includes limits.h. Normally if the file would've not be
there it would have used the embedded one from gcc but now there is a
file there and it uses it. The bad point is limits.h indirectly
includes linux/limits.h and the do_configure step from
nativesdk-libgcc-initial fails :-(

I see multiple issues here and would be glad to get your opinion on
how to solve them properly:
First problem skipped tasks and missing do_package entries in the sstate.
Second the race condition with nativesdk-libgcc-initial.

Best wishes
Dimitar

-- 
BMW Car IT GmbH
Dimitar Yordanov
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89081 Ulm
Tel.: +49-731-37804-290
Fax: +49-731 378040-01
Mail: dimitar.yordanov at bmw-carit.de
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