On Wed, 2019-04-03 at 18:48 +0800, Weiping Zhang wrote:
> Could you point out the race case for udev?
Hi Weiping,
A quote from Documentation/kobject.txt:
"Use the KOBJ_ADD action for when the kobject is first added to the kernel.
This should be done only after any attributes or children of the kobject
have been initialized properly, as userspace will instantly start to look
for them when this call happens."
You may want to have a look at commit 33b14f67a4e1 ("nvme: register ns_id
attributes as default sysfs groups") as an example of a patch that fixes a
race condition between sysfs attribute creation and udev.
Regarding the block layer timeout attribute: I just noticed that for the
request queue kobj attribute KOBJ_ADD is triggered explicitly from
blk_register_queue():
kobject_uevent(&q->kobj, KOBJ_ADD);
Your patch adds sysfs attributes before that code is encountered so it should
be fine.
Bart.
