margay fails assertion in stats/dsa/dsm code

Hi,

BF animal margay (a newly started Solaris 11.4/Sparc/GCC 11.2 box) is
sometimes failing with:

TRAP: FailedAssertion("seg->mapped_address != NULL", File: "dsm.c",
Line: 1069, PID: 9038)

I can't immediately see why it's doing this, but my tool that looks
for assertion failures hasn't seen that on any other system. Example
stack (trimmed from log), in this case a regular backend, other times
it was a parallel worker:

TRAP: FailedAssertion("seg->mapped_address != NULL", File: "dsm.c",
Line: 1069, PID: 3944)
ExceptionalCondition+0x64 [0x1008bb348]
dsm_segment_address+0x44 [0x1006ff7d0]
get_segment_by_index+0x7c [0x1008ee960]
dsa_get_address+0x9c [0x1008ef754]
pgstat_get_entry_ref+0x1068 [0x10075f348]
pgstat_prep_pending_entry+0x58 [0x100758424]
pgstat_assoc_relation+0x44 [0x10075b314]
_bt_first+0x9ac [0x10036cd78]
btgettuple+0x10c [0x1003653a8]
index_getnext_tid+0x4c [0x1003531c4]
index_getnext_slot+0x78 [0x100353564]
systable_getnext+0x18 [0x1003519b4]
SearchCatCacheMiss+0x74 [0x10089ce18]
SearchCatCacheInternal+0x1c0 [0x10089d0a4]
GetSysCacheOid+0x34 [0x1008b5ca4]
get_role_oid+0x18 [0x100767444]
hba_getauthmethod+0x8 [0x100599da4]
ClientAuthentication+0x1c [0x10058cb68]
InitPostgres+0xacc [0x1008d26b8]
PostgresMain+0x94 [0x1007397f8]
ServerLoop+0x1184 [0x1006739e8]
PostmasterMain+0x1400 [0x10067520c]
main+0x2e0 [0x1005a28c0]
_start+0x64 [0x1002c5c44]

I know that on Solaris we use dynamic_shared_memory=posix. The other
Solaris/Sparc system is wrasse, and it's not doing this. I don't see
it yet, but figured I'd report this much to the list in case someone
else does.