From: Linus Torvalds Date: Mon, 26 Jan 2015 23:17:34 +0000 (-0800) Subject: Merge branch 'for-3.19-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup X-Git-Tag: v3.19-rc7~27 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c976a67b02821d324f5e9fffe87e807364fe1a0e;p=linux.git Merge branch 'for-3.19-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup fix from Tejun Heo: "The lifetime rules of cgroup hierarchies always have been somewhat counter-intuitive and cgroup core tried to enforce that hierarchies w/o userland-visible usages must die in finite amount of time so that the controllers can be reused for other hierarchies; unfortunately, this can't be implemented reasonably for the memory controller - the kmemcg part doesn't have any way to forcefully drain the existing usages, leading to an interruptible hang if a following mount attempts to use the controller in any way. So, it seems like we're stuck with "hierarchies live on till they die whenever that may be" at least for now. This pretty much confines attaching controllers to hierarchies to before the hierarchies are actively used by making dynamic configurations post active usages unreliable. This has never been reliable and should be fine in practice given how cgroups are used. After the patch, hierarchies aren't killed if it isn't already drained. A following mount attempt of the same mount options will reuse the existing hierarchy. Mount attempts with differing options will fail w/ -EBUSY" * 'for-3.19-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: prevent mount hang due to memory controller lifetime --- c976a67b02821d324f5e9fffe87e807364fe1a0e