From: Dan Williams <dan.j.williams@xxxxxxxxx> Subject: mm: validate device_hotplug is held for memory hotplug mem_hotplug_begin() assumes that it can set mem_hotplug.active_writer and run the hotplug process without racing another thread. Validate this assumption with a lockdep assertion. Link: http://lkml.kernel.org/r/148693886229.16345.1770484669403334689.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> Reported-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Toshi Kani <toshi.kani@xxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Logan Gunthorpe <logang@xxxxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Masayoshi Mizuma <m.mizuma@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/base/core.c | 5 +++++ include/linux/device.h | 1 + mm/memory_hotplug.c | 2 ++ 3 files changed, 8 insertions(+) diff -puN drivers/base/core.c~mm-validate-device_hotplug-is-held-for-memory-hotplug drivers/base/core.c --- a/drivers/base/core.c~mm-validate-device_hotplug-is-held-for-memory-hotplug +++ a/drivers/base/core.c @@ -638,6 +638,11 @@ int lock_device_hotplug_sysfs(void) return restart_syscall(); } +void assert_held_device_hotplug(void) +{ + lockdep_assert_held(&device_hotplug_lock); +} + #ifdef CONFIG_BLOCK static inline int device_is_not_partition(struct device *dev) { diff -puN include/linux/device.h~mm-validate-device_hotplug-is-held-for-memory-hotplug include/linux/device.h --- a/include/linux/device.h~mm-validate-device_hotplug-is-held-for-memory-hotplug +++ a/include/linux/device.h @@ -1139,6 +1139,7 @@ static inline bool device_supports_offli extern void lock_device_hotplug(void); extern void unlock_device_hotplug(void); extern int lock_device_hotplug_sysfs(void); +void assert_held_device_hotplug(void); extern int device_offline(struct device *dev); extern int device_online(struct device *dev); extern void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode); diff -puN mm/memory_hotplug.c~mm-validate-device_hotplug-is-held-for-memory-hotplug mm/memory_hotplug.c --- a/mm/memory_hotplug.c~mm-validate-device_hotplug-is-held-for-memory-hotplug +++ a/mm/memory_hotplug.c @@ -126,6 +126,8 @@ void put_online_mems(void) void mem_hotplug_begin(void) { + assert_held_device_hotplug(); + mem_hotplug.active_writer = current; memhp_lock_acquire(); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
