On Fri, Aug 06, 2021 at 05:22:08PM +0200, Mete Polat wrote:
Commit e977145aeaad ("[RBTREE] Add explicit alignment to sizeof(long) for
struct rb_node.") adds an explicit alignment to the struct rb_node due to
some speciality of the CRIS architecture.
The support for the CRIS architecture was removed with commit c690eddc2f3b
("CRIS: Drop support for the CRIS port")
So, remove this now unneeded explicit alignment in struct rb_node as well.
This basically reverts commit e977145aeaad ("[RBTREE] Add explicit
alignment to sizeof(long) for struct rb_node.").
The rbtree node color is stored in the LSB of '__rb_parent_color'.
Only mask the first bit in '__rb_parent()', otherwise it modifies the
node's parent address on m68k.
I still don't believe for a second this will actually work. We rely on
rcu_assign_pointer() and rcu_dereference() to work on the
rb_{left,right} members, and I don't think any architecture can provide
single copy atomic loads and stores that are not naturally aligned (eg.
when they straddle a cache or page boundary).
