Messages in this thread | | | Date | Mon, 25 Oct 2010 09:15:36 +0800 | From | Li Zefan <> | Subject | Re: [PATCH 5/7] cgroups: Make freezer subsystem bindable |
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Matt Helsley wrote: > On Fri, Oct 22, 2010 at 04:11:41PM +0800, Li Zefan wrote: >> To make it bindable, we need to thaw all processes when unbinding >> the freezer subsystem from a cgroup hierarchy. >> >> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> > > Based on experience using cgroups and questions we've fielded in the > past on IRC I'd say users will really appreciate this. > > We're planning to use the freezer in checkpoint/restart. Since > checkpoint requires the tasks to remain frozen for the duration of > the syscall we add a kernel-internal freezer subsystem interface > which prevents the cgroup from thawing. So we'll need some way to > "block" unbinding for that as well. >
How about, we allow unbinding only when all the cgroups' state is THAWED ?
> Perhaps the bind op should be able to return an error when > unbind == true? Although that raises the question of what to do if > only one of multiple unbinds fails.. > > Alternately you could split the bind/unbind op function pointers > and get rid of the boolean argument. Then just don't fill in the > freezer's unbind op and refuse to unbind subsystems that lack > the unbind op. That seems a bit cleaner for now at least. >
We can use bindable:1 along with a callback can_bind().
For some subsystems, we just set bindable to true. For freezer subsystem, we set it to true and provide freezer_can_bind(), and return true only if no cgroup's state is FROZEN.
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