565851c972
Usage of device_lock() for dax_region attributes is unnecessary and
deadlock prone. It's unnecessary because the order of registration /
un-registration guarantees that drvdata is always valid. It's deadlock
prone because it sets up this situation:
ndctl D 0 2170 2082 0x00000000
Call Trace:
__schedule+0x31f/0x980
schedule+0x3d/0x90
schedule_preempt_disabled+0x15/0x20
__mutex_lock+0x402/0x980
? __mutex_lock+0x158/0x980
? align_show+0x2b/0x80 [dax]
? kernfs_seq_start+0x2f/0x90
mutex_lock_nested+0x1b/0x20
align_show+0x2b/0x80 [dax]
dev_attr_show+0x20/0x50
ndctl D 0 2186 2079 0x00000000
Call Trace:
__schedule+0x31f/0x980
schedule+0x3d/0x90
__kernfs_remove+0x1f6/0x340
? kernfs_remove_by_name_ns+0x45/0xa0
? remove_wait_queue+0x70/0x70
kernfs_remove_by_name_ns+0x45/0xa0
remove_files.isra.1+0x35/0x70
sysfs_remove_group+0x44/0x90
sysfs_remove_groups+0x2e/0x50
dax_region_unregister+0x25/0x40 [dax]
devm_action_release+0xf/0x20
release_nodes+0x16d/0x2b0
devres_release_all+0x3c/0x60
device_release_driver_internal+0x17d/0x220
device_release_driver+0x12/0x20
unbind_store+0x112/0x160
ndctl/2170 is trying to acquire the device_lock() to read an attribute,
and ndctl/2186 is holding the device_lock() while trying to drain all
active attribute readers.
Thanks to Yi Zhang for the reproduction script.
Fixes:
|
||
|---|---|---|
| .. | ||
| dax-private.h | ||
| dax.c | ||
| dax.h | ||
| Kconfig | ||
| Makefile | ||
| pmem.c | ||