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Re: slapd-mtread crash on ppc64{,el} in stretch/sid

Control: notforwarded -1
Control: reassign -1 src:linux 4.8.7-1
Control: affects -1 src:openldap

Hi debian-kernel,

There seems to be a regression on powerpc64 (both endians) that can corrupt the vector-scalar registers (VSRs) in a threaded program.

I believe the bad commit is this one:

4.9.0: https://github.com/torvalds/linux/commit/dc16b553c949e81f37555777dc7bab66d78285a7
4.8.6: https://github.com/linux-stable/linux-stable/commit/613036d9e91990f2043130ff8f78fd770432b3de

My program is not using transactional memory itself, but I don't know what libc/libpthread might do internally.

4.8.7-1 is the first Debian kernel where I observe the crash. I rebuilt that package with the above commit reverted and it went away.

The crash still occurs with 4.11.6-1 from unstable. I have not tested anything more recent.

I still need to work up a reduced test case. For now the steps to reproduce the crash with the openldap package are:

 apt-get build-dep openldap
 apt-get source openldap
 cd openldap-*/
 DEB_BUILD_OPTIONS=nocheck dpkg-buildpackage -T build
 cd debian/build/tests
 ./run -b bdb test060-mt-hot


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