On Fri, May 23, 2014 at 8:27 PM, DX Cui <rijcos@xxxxxxxxx> wrote: > Hi all, > I think I found out the root cause: when memory hotplug was introduced in 2005: > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3947be1969a9ce455ec30f60ef51efb10e4323d1 > there was a race condition in: > > + static int add_memory_block(unsigned long node_id, struct > mem_section *section, > + unsigned long state, int phys_device) > +{ > ... > + ret = register_memory(mem, section, NULL); > + if (!ret) > + ret = mem_create_simple_file(mem, phys_index); > + if (!ret) > + ret = mem_create_simple_file(mem, state); > > Here, first, add_memory_block() invokes register_memory() -> > sysdev_register() -> sysdev_add()-> > kobject_uevent(&sysdev->kobj, KOBJ_ADD) to notify udev daemon, then > invokes mem_create_simple_file(). If the current execution is preempted > between the 2 steps, the issue I reported in the previous mail can happen. > > Luckily a commit in 2013 has fixed this issue undesignedly: > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=96b2c0fc8e74a615888e2bedfe55b439aa4695e1 > > It looks the new "register_memory() --> ... -> device_add()" path has the > correct order for sysfs creation and notification udev. > > It would be great if you can confirm my analysis. :-) Any comments? I think we need to backport the patch 96b2c0fc8e74a615888e2bedfe55b439aa4695e1 to <=3.9 stable kernels. -- DX -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>