Avoid lockup of a parallel worker when reporting a long error message.
Because sigsetjmp() will restore the initial state with signals blocked,
the code path in bgworker.c for reporting an error and exiting would
execute that way. Usually this is fairly harmless; but if a parallel
worker had an error message exceeding the shared-memory communication
buffer size (16K) it would lock up, because it would wait for a
resume-sending signal from its parallel leader which it would never
detect.
To fix, just unblock signals at the appropriate point.
This can be shown to fail back to 9.6. The lack of parallel query
infrastructure makes it difficult to provide a simple test case for
9.5; but I'm pretty sure the issue exists in some form there as well,
so apply the code change there too.
Vignesh C, reviewed by Bharath Rupireddy, Robert Haas, and myself
Discussion: https://postgr.es/m/CALDaNm1d1hHPZUg3xU4XjtWBOLCrA+-2cJcLpw-cePZ=GgDVfA@mail.gmail.com
Branch
------
REL_12_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/82dd373f2c56f7b32a3304260195fdaf6ed7cd9c
Modified Files
--------------
src/backend/postmaster/bgworker.c | 11 +++++++++--
src/test/regress/expected/select_parallel.out | 5 +++--
src/test/regress/sql/select_parallel.sql | 3 ++-
3 files changed, 14 insertions(+), 5 deletions(-)
