commit 3fc21924100b13f73c734d0ce8dfcfe913fcf7a8
author Dan Williams <dan.j.williams@intel.com> Fri Feb 24 14:55:48 2017 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> Fri Feb 24 17:46:53 2017 -0800
tree 3d9f46a4936f591e5e306cf909e44fe6012efe89
parent b5d24fda9c3dce51fcb4eee459550a458eaaf1e2

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@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/core.c

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 8c25e68..3050e6f 100644
--- a/drivers/base/core.c
+++ b/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)
 {

include/linux/device.h

diff --git a/include/linux/device.h b/include/linux/device.h
index bd684fc..a48a7ff 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1139,6 +1139,7 @@ static inline bool device_supports_offline(struct device *dev)
 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);

mm/memory_hotplug.c

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index d67787d..92a242a 100644
--- a/mm/memory_hotplug.c
+++ b/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();