Percona Server failure after upgrade attempt

I was upgrading a MySQL server from MySQL 5.1 to MySQL 5.5 and then to Percona Server 5.6 on several replication slaves (in place upgrade). The upgrade to MySQL 5.5 worked fine but whenever I tried to upgrade to Percona Server 5.6, I kept seeing these assertion errors in the log file. It didn't happen every server but on several of them.

2016-08-03 15:57:15 10110 [Warning] InnoDB: Resizing redo log from 2*65536 to 2*131072 pages, LSN=25951778491874
2016-08-03 15:57:15 10110 [Warning] InnoDB: Starting to delete and rewrite log files.
2016-08-03 15:57:16 10110 [Note] InnoDB: Setting log file ./ib_logfile101 size to 2048 MB
InnoDB: Progress in MB: 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
2016-08-03 15:57:20 10110 [Note] InnoDB: Setting log file ./ib_logfile1 size to 2048 MB
InnoDB: Progress in MB: 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
2016-08-03 15:57:26 10110 [Note] InnoDB: Renaming log file ./ib_logfile101 to ./ib_logfile0
2016-08-03 15:57:26 10110 [Warning] InnoDB: New log files created, LSN=25951778491916
2016-08-03 15:57:26 7fc770a50740  InnoDB: Assertion failure in thread 140494565082944 in file pars0pars.cc line 865
InnoDB: Failing assertion: sym_node->table != NULL
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.6/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
21:57:26 UTC - mysqld got signal 6 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.
Please help us make Percona Server better by reporting any
bugs at http://bugs.percona.com/

key_buffer_size=67108864
read_buffer_size=131072
max_used_connections=0
max_threads=100001
thread_count=0
connection_count=0
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 217676709 K  bytes of memory
Hope that's ok; if not, decrease some variables in the equation.

Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0 thread_stack 0x40000
/usr/sbin/mysqld(my_print_stacktrace+0x20)[0x893c80]
/usr/sbin/mysqld(handle_fatal_signal+0x348)[0x655d48]
/lib64/libpthread.so.0(+0xfeb0)[0x7fc76f5bfeb0]
/lib64/libc.so.6(gsignal+0x37)[0x7fc76ea2f237]
/lib64/libc.so.6(abort+0x148)[0x7fc76ea30578]
/usr/sbin/mysqld[0x9882ca]
/usr/sbin/mysqld[0x989946]
/usr/sbin/mysqld(_Z7yyparsev+0xb39)[0xa97a79]
/usr/sbin/mysqld[0x98af5e]
/usr/sbin/mysqld[0x98e1c3]
/usr/sbin/mysqld[0x9aed1b]
/usr/sbin/mysqld[0x9b075a]
/usr/sbin/mysqld[0x969f96]
/usr/sbin/mysqld[0x9d3697]
/usr/sbin/mysqld[0x92e6fa]
/usr/sbin/mysqld(_Z24ha_initialize_handlertonP13st_plugin_int+0x41)[0x5a9cd1]
/usr/sbin/mysqld[0x6d6e20]
/usr/sbin/mysqld(_Z11plugin_initPiPPci+0x915)[0x6db165]
/usr/sbin/mysqld[0x5a0234]
/usr/sbin/mysqld(_Z11mysqld_mainiPPc+0x385)[0x5a3565]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7fc76ea1ba65]
/usr/sbin/mysqld[0x598075]
You may download the Percona Server operations manual by visiting
http://www.percona.com/software/percona-server/. You may find information
in the manual which will help you identify the cause of the crash.

The error message is obscure, after testing several different paths, I finally found one that worked.

Things I tried:

• shutting down with innodb_fast_shutdown  = 0
• Running check/repair on all tables
• Wiped out data and restored a copy of the data from the master.

What worked:

• innodb_fast_shutdown = 0 on MySQL 5.5.
• Deleted the innodb log files.
• Started MySQL again.
• Shutdown again with the fast shutdown, still on MySQL 5.5.
• Upgraded MySQL to Percona Server 5.6, using basic same my.cnf file.
• Started Percon Server 5.6. Then made changes to the my.cnf file and restarted again.