Messages in this thread | | | Subject | cgroup umount bug | From | 含黛 <> | Date | Sat, 8 Oct 2011 20:02:24 +0800 |
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Hi,
I found a mount/umount problem while using cgroup: I mount a cpu cgroup (or other subsystems) and create some subgroups under it, but later I try to umount it without rmdir those subgroups. I find that I can umount it without any errors but actually the super block still exist. This is because the sb->s_active count is greater than 1 which was added by cgroup_create. But later if I want to mount both cpu and memory subsystems, it will be unsuccessful indicating that the device(cpu subsystem) is busy. This situation will not happen if I rmdir the subgroups manually before umount it. So my question is: Should the umount return success when there are still some subgroups exist ? If this is okay, then it may lead to some *strange* errors using cgroup later. If it can not be umount, then it should inform that the mount point is still busy.
Following is an example of this problem:
mount -t cgroup -o cpu cgroup /mnt mkdir /mnt/test
…..// do some tests
umount /mnt /* return successfully */
/* do other subsystems test */ mount -cgroup -o cpu,cpuset cgroup /mnt mount: cgroup already mounted or /mnt busy /*??? which is strange */
Looking forward to your reply. Thanks.
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