Assertion failure with barriers in parallel hash join

Hi all,

prion, that uses -DRELCACHE_FORCE_RELEASE -DCATCACHE_FORCE_RELEASE,
has just failed with an interesting failure:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=prion&dt=2020-09-29%2005%3A24%3A11

The assertion failure happens in a parallel worker when attempting to
attach a barrier:
#2 0x00000000009027d2 in ExceptionalCondition
(conditionName=conditionName(at)entry=0xa80846 "!barrier->static_party",
errorType=errorType(at)entry=0x955e22 "FailedAssertion",
fileName=fileName(at)entry=0xa807a8
"/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/storage/ipc/barrier.c",
lineNumber=lineNumber(at)entry=218) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/utils/error/assert.c:67
#3 0x00000000007b6b1f in BarrierAttach
(barrier=barrier(at)entry=0x7f73c9d76008) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/storage/ipc/barrier.c:218
#4 0x0000000000682ebf in ExecParallelHashJoinNewBatch
(hjstate=<optimized out>, hjstate=<optimized out>) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/executor/nodeHashjoin.c:1132
#5 ExecHashJoinImpl (parallel=true, pstate=0x1248d88) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/executor/nodeHashjoin.c:560
#6 ExecParallelHashJoin (pstate=0x1248d88) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/executor/nodeHashjoin.c:607
#7 0x0000000000666d48 in ExecProcNodeInstr (node=0x1248d88) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/backend/executor/execProcnode.c:466
#8 0x000000000065f322 in ExecProcNode (node=0x1248d88) at
/home/ec2-user/bf/root/REL_13_STABLE/pgsql.build/../pgsql/src/include/executor/executor.h:245

Thanks,
--
Michael