Messages in this thread | | | Date | Tue, 23 Feb 2010 12:58:46 +0100 | From | Andrea Righi <> | Subject | Re: [PATCH 1/2] memcg: dirty pages accounting and limiting infrastructure |
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On Mon, Feb 22, 2010 at 01:07:32PM -0500, Vivek Goyal wrote: > > > > +unsigned long mem_cgroup_dirty_bytes(void) > > > > +{ > > > > + struct mem_cgroup *memcg; > > > > + unsigned long dirty_bytes; > > > > + > > > > + if (mem_cgroup_disabled()) > > > > + return vm_dirty_bytes; > > > > + > > > > + rcu_read_lock(); > > > > + memcg = mem_cgroup_from_task(current); > > > > + if (memcg == NULL) > > > > + dirty_bytes = vm_dirty_bytes; > > > > + else > > > > + dirty_bytes = get_dirty_bytes(memcg); > > > > + rcu_read_unlock(); > > > > > > The rcu_read_lock() isn't protecting anything here. > > > > Right! > > Are we not protecting "memcg" pointer using rcu here?
Vivek, you are right:
mem_cgroup_from_task() -> task_subsys_state() -> rcu_dereference()
So, this *must* be RCU protected.
Thanks! -Andrea
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