On Sun, May 10, 2020 at 09:29:05AM -0400, Andrew Dunstan wrote:
> On 4/18/20 9:15 AM, Andrew Dunstan wrote:
> > I was just trying to revive lousyjack, my valgrind buildfarm animal
> > which has been offline for 12 days, after having upgraded the machine
> > (fedora 31, gcc 9.3.1, valgrind 3.15) and noticed lots of errors like this:
> > {
> > <insert_a_suppression_name_here>
> > Memcheck:Value8
> > fun:pg_comp_crc32c_sb8
> > fun:XLogRecordAssemble
> > fun:XLogInsert
> > fun:LogCurrentRunningXacts
> > fun:LogStandbySnapshot
> > fun:CreateCheckPoint
> > fun:CheckpointerMain
> > fun:AuxiliaryProcessMain
> > fun:StartChildProcess
> > fun:reaper
> > obj:/usr/lib64/libpthread-2.30.so
> > fun:select
> > fun:ServerLoop
> > fun:PostmasterMain
> > fun:main
> > }
> After many hours of testing I have a culprit for this. The error appears
> with valgrind 3.15.0 with everything else held constant. 3.14.0 does
> not produce the problem.
I suspect 3.15.0 is just better at tracking the uninitialized data. A
more-remote possibility is valgrind-3.14.0 emulating sse42. That would make
pg_crc32c_sse42_available() return true, avoiding the pg_comp_crc32c_sb8().
> andrew@freddo:bf (master)*$ lscpu
...
> Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr
> pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext
> fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl
> nonstop_tsc cpuid extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy
> svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs
> skinit wdt hw_pstate vmmcall npt lbrv svm_lock nrip_save
>
>
> I did not manage to reproduce this anywhere else, tried on various
> physical, Virtualbox and Docker instances.
I can reproduce this on a 2017-vintage CPU with ./configure
... USE_SLICING_BY_8_CRC32C=1 and then running "make installcheck-parallel"
under valgrind-3.15.0 (as packaged by RHEL 7.8). valgrind.supp has a
suppression for CRC calculations, but it didn't get the memo when commit
4f700bc renamed the function. The attached patch fixes the suppression.