On Wed, Aug 18, 2021 at 03:00:59PM +0000, Jelte Fennema wrote: > I ran into some segfaults when using Postgres that was compiled with LLVM 7. > According to the backtraces these crashes happened during the call to > llvm_shutdown, during cleanup after another out of memory condition. It seems > that calls to LLVMOrcDisposeInstance, can crash (at least on LLVM 7) when > LLVM is left in bad state. I attached the relevant part of the stacktrace to > this email. > > With the attached patch these segfaults went away. The patch turns > llvm_shutdown into a no-op whenever the backend is exiting with an error. > Based on my understanding of the code this should be totally fine. No memory > should be leaked, since all memory will be cleaned up anyway once the backend > exits shortly after. The only reason this cleanup code even seems to exist at > all is to get useful LLVM profiling data. To me it seems be acceptable if the > profiling data is incorrect/missing when the backend exits with an error.
Andres , could you comment on this ? This seems to explain the crash I reported to you when testing your WIP patches for the JIT memory leak. I realize now that the crash happens without your patches. https://www.postgresql.org/message-id/20210419164130.byegpfrw46mza...@alap3.anarazel.de I can reproduce the crash on master (not just v13, as I said before) compiled on centos7, with: LLVM_CONFIG=/usr/lib64/llvm7.0/bin/llvm-config CLANG=/opt/rh/llvm-toolset-7.0/root/usr/bin/clang I cannot reproduce the crash after applying Jelte's patch. I couldn't crash on ubuntu either, so maybe they have a patch which fixes this, or maybe RH applied a patch which caused it... postgres=# CREATE TABLE t AS SELECT i FROM generate_series(1,999999)i; VACUUM ANALYZE t; postgres=# SET client_min_messages=debug; SET statement_timeout=333; SET jit_above_cost=0; SET jit_optimize_above_cost=-1; SET jit_inline_above_cost=-1; explain analyze SELECT sum(i) FROM t a NATURAL JOIN t b; 2021-09-05 22:47:12.807 ADT client backend[7563] psql ERROR: canceling statement due to statement timeout 2021-09-05 22:47:12.880 ADT postmaster[7272] LOG: background worker "parallel worker" (PID 8212) was terminated by signal 11: Segmentation fault -- Justin
