On Wed, 2019-04-03 at 18:48 +-0800, Weiping Zhang wrote: +AD4 Could you point out the race case for udev? Hi Weiping, A quote from Documentation/kobject.txt: +ACI-Use the KOBJ+AF8-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.+ACI You may want to have a look at commit 33b14f67a4e1 (+ACI-nvme: register ns+AF8-id attributes as default sysfs groups+ACI) 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+AF8-ADD is triggered explicitly from blk+AF8-register+AF8-queue(): kobject+AF8-uevent(+ACY-q-+AD4-kobj, KOBJ+AF8-ADD)+ADs Your patch adds sysfs attributes before that code is encountered so it should be fine. Bart.
