Are handlerton->commit calls serialized in MySQL 5.6?

[Zardosht Kasheff]

Hello all,

In http://lists.mysql.com/internals/38715, I learned quite a bit about
MySQL 5.6 replication, but also saw something interesting that I would
like to learn more about.

As covered in that thread, handlerton->commit calls made with
thd->durability_properties set to HA_IGNORE_DURABILITY means the
enginecan ignore the durability requirements of commits.

However, I also saw that such calls are serialized under some global
mutex. Is this accurate? Is this mutex a MySQL mutex or an InnoDB
mutex? If so, how is concurrency affected? Is this any different than
how MySQL 5.5 behaves?

Thanks
-Zardosht