Another one:

+bt
#0  0x00007f5b5a3a3741 in __pthread_kill (threadid=<optimized out>, signo=11) at ../nptl/sysdeps/unix/sysv/linux/pthread_kill.c:61
#1  0x0000000000abf206 in my_write_core (sig=11) at /git/PS-5.6.30_dbg/mysys/stacktrace.c:422
#2  0x0000000000735c63 in handle_fatal_signal (sig=11) at /git/PS-5.6.30_dbg/sql/signal_handler.cc:236
#3  <signal handler called>
#4  0x0000000000e6acd6 in my_lfind (head=0x7f5a84046528, cs=0x1501e20 <my_charset_bin>, hashnr=620756992, key=0x108ae5a "", keylen=0, cursor=0x7f5b5a9a6ed0, pins=0x7f5a84093ec0) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:95
#5  0x0000000000e6aecd in linsert (head=0x7f5a84046528, cs=0x1501e20 <my_charset_bin>, node=0x7f5a840ed4a0, pins=0x7f5a84093ec0, flags=1) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:161
#6  0x0000000000e6b952 in initialize_bucket (hash=0x17ee180 <digest_hash>, node=0x7f5a84046928, bucket=164, pins=0x7f5a84093ec0) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:490
#7  0x0000000000e6b8f0 in initialize_bucket (hash=0x17ee180 <digest_hash>, node=0x7f5a8409c728, bucket=1188, pins=0x7f5a84093ec0) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:485
#8  0x0000000000e6b8f0 in initialize_bucket (hash=0x17ee180 <digest_hash>, node=0x7f5a840c2928, bucket=3236, pins=0x7f5a84093ec0) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:485
#9  0x0000000000e6b8f0 in initialize_bucket (hash=0x17ee180 <digest_hash>, node=0x7f5a840c1f28, bucket=7332, pins=0x7f5a84093ec0) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:485
#10 0x0000000000e6b7e3 in lf_hash_search (hash=0x17ee180 <digest_hash>, pins=0x7f5a84093ec0, key=0x7f5b5a9a70f0, keylen=212) at /git/PS-5.6.30_dbg/mysys/lf_hash.c:460
#11 0x0000000000adf05e in find_or_create_digest (thread=0x7f5b3f61c200, digest_storage=0x7f5b56ab8450, schema_name=0x7f5b56ab8538 "test", schema_name_length=4) at /git/PS-5.6.30_dbg/storage/perfschema/pfs_digest.cc:223
#12 0x0000000000b14954 in end_statement_v1 (locker=0x7f5b56ab8490, stmt_da=0x7f5b56ab9c78) at /git/PS-5.6.30_dbg/storage/perfschema/pfs.cc:4815
#13 0x00000000007e2ad8 in inline_mysql_end_statement (locker=0x7f5b56ab8490, stmt_da=0x7f5b56ab9c78) at /git/PS-5.6.30_dbg/include/mysql/psi/mysql_statement.h:215
#14 0x00000000007e788b in dispatch_command (command=COM_QUERY, thd=0x7f5b56ab6800, packet=0x7f5aa3b2e9c1 "", packet_length=37) at /git/PS-5.6.30_dbg/sql/sql_parse.cc:1893
#15 0x00000000007e519f in do_command (thd=0x7f5b56ab6800) at /git/PS-5.6.30_dbg/sql/sql_parse.cc:1053
#16 0x00000000007ac701 in do_handle_one_connection (thd_arg=0x7f5b56ab6800) at /git/PS-5.6.30_dbg/sql/sql_connect.cc:1541
#17 0x00000000007ac181 in handle_one_connection (arg=0x7f5b56ab6800) at /git/PS-5.6.30_dbg/sql/sql_connect.cc:1444
#18 0x0000000000b0e4c9 in pfs_spawn_thread (arg=0x7f5b3cd789a0) at /git/PS-5.6.30_dbg/storage/perfschema/pfs.cc:1860
#19 0x00007f5b5a39edc5 in start_thread (arg=0x7f5b5a9a8700) at pthread_create.c:308
#20 0x00007f5b587fd21d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113

Testcase that seems to be (sporadically?) reproducible on 5.6.30;

MYEXTRA=" --no-defaults --log-output=none --sql_mode=ONLY_FULL_GROUP_BY --plugin-load-add=audit_log=audit_log.so --plugin-load-add=tokudb=ha_tokudb.so --init-file=/home/roel/percona-qa/plugins.sql --tokudb-check-jemalloc=0 --innodb-log-checksum-algorithm=none --innodb-ft-result-cache-limit=1 --enforce-storage-engine=BLACKHOLE --eq-range-index-dive-limit=1023 --innodb-old-blocks-pct=24 --enforce-storage-engine=CSV --console=0 --innodb-stats-transient-sample-pages=1 --tokudb-lock-timeout=12 --tokudb-auto-analyze=1023 --tokudb_read_block_size=33000 --tokudb-loader-memory-size=2 --tokudb-read-status-frequency=1023"

DROP DATABASE test;CREATE DATABASE test;USE test;
CREATE TABLE t1 (f1 INT, f2 INT );
insert INTO t1  values('TKF','Seattle','WA','AME');
SET GLOBAL scalability_metrics_control = OFF;
SET GLOBAL scalability_metrics_control = ON;
set global innodb_large_prefix='AUTO';