tree 6b88b2b043cac10b34234320c68e06848c00127c
parent aa94b5371f6f898558d9fa5690cc6e4bf917a572
author Jens Axboe <jens.axboe@oracle.com> 1210144632 +0200
committer Jens Axboe <jens.axboe@oracle.com> 1210145337 +0200

cfq-iosched: fix RCU race in the cfq io_context destructor handling

put_io_context() drops the RCU read lock before calling into cfq_dtor(),
however we need to hold off freeing there before grabbing and
dereferencing the first object on the list.

So extend the rcu_read_lock() scope to cover the calling of cfq_dtor(),
and optimize cfq_free_io_context() to use a new variant for
call_for_each_cic() that assumes the RCU read lock is already held.

Hit in the wild by Alexey Dobriyan <adobriyan@gmail.com>

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>