On Wed, Feb 01, 2012 at 04:19:18PM +0100, Jan Kara wrote: > We actually spotted this race in practice in btrfs on structure > fs/btrfs/ctree.h:struct btrfs_block_rsv where spinlock content got > corrupted due to update of following bitfield and there seem to be other > places in kernel where this could happen.
Here's the list of structures where a bitfield is shared with spinlock or atomic/kref within an 8B word, generated from 3.3-rc2: spinlock+bitfield: Struct: struct ak4113; Field: init Struct: struct ak4114; Field: init Struct: struct ak4117; Field: init Struct: struct btrfs_block_rsv; Field: full Struct: struct cm109_dev; Field: buzzer_pending Struct: struct pch_udc_dev; Field: active Struct: struct rds_iw_device; Field: dma_local_lkey Struct: struct sierra_intf_private; Field: suspended Struct: struct sm501_gpio; Field: registered Struct: struct unix_sock; Field: gc_candidate Struct: struct usb_anchor; Field: poisoned Struct: struct usb_wwan_intf_private; Field: suspended atomic/kref+bitfield: Struct: struct dlm_lock_resource; Field: migration_pending Struct: struct extent_map; Field: in_tree Struct: struct kobject; Field: state_initialized Struct: struct page; Field: inuse Struct: struct rds_ib_connection; Field: i_flowctl Struct: struct rds_iw_connection; Field: i_flowctl Struct: struct sctp_transport; Field: dead Struct: struct transaction_s; Field: t_synchronous_commit Struct: struct xfs_ioend; Field: io_isasync Not all listed structs are necessarily subject to the bug. There may be another mechanism preventing concurrent access to the bitfield and spinlock/atomic, or the bitfield is modified from a single cpu, or is not used. But all of them need to be reviewed of course. david
