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Crashes after updating microcode-data

Today Gentoo released the Intel Microcode update: sys-apps/microcode-data-20150121
After installation immediately a lot of applications crashed with the following log:
kernel: traps: NetworkManager[1308] trap invalid opcode ip:7f8bba0b093a sp:7fffd40a22e8 error:0 in libpthread-2.20.so[7f8bba0a5000+16000]

Some research revealed that this machine has an Intel Haswell CPU with buggy TSX. And the microcode update fixes this by effectively disabling TSX. This in itself is not a problem yet.

The most popular code that uses TSX is libpthread of glibc. And I had used an too old gcc version to compile glibc, with -march=native in CFLAGS. Unfortunately this gcc version enables TSX (hle, rtm) with the native optimizations enabled. So everything crashed at once.

The fix was to simply recompile glibc with gcc-4.8.4:
# gcc-config -l
 [1] x86_64-pc-linux-gnu-4.8.4 *
# emerge -1 glibc
You can check if gcc disables hle and rtm on your Haswell CPU correctly:
$ gcc -march=native -E -v - </dev/null 2>&1 | sed -n 's/.* -v - //p'
-march=core-avx2 -mcx16 -msahf -mmovbe -maes -mpclmul -mpopcnt -mabm -mno-lwp -mfma -mno-fma4 -mno-xop -mbmi -mbmi2 -mno-tbm -mavx -mavx2 -msse4.2 -msse4.1 -mlzcnt -mno-rtm -mno-hle -mrdrnd -mf16c -mfsgsbase -mno-rdseed -mno-prfchw -mno-adx -mfxsr -mxsave -mxsaveopt --param l1-cache-size=32 --param l1-cache-line-size=64 --param l2-cache-size=6144 -mtune=core-avx2 -fstack-protector



posted on 2015-04-15 14:30 CEST in Code | 0 comments | permalink