On 10/30/2014 04:27 AM, Michal Hocko wrote: > On Wed 29-10-14 21:44:24, Sasha Levin wrote: >> > Commit "mm: memcontrol: fix missed end-writeback page accounting" has changed >> > the behaviour of mem_cgroup_begin_page_stat() to not always set the "locked" >> > parameter. >> > >> > We should initialize it at the callers to prevent garbage being used in a >> > later call to mem_cgroup_end_page_stat(). > The contract is that if the returned memcg is non-NULL then the locked > is always initialized. Nobody but mem_cgroup_end_page_stat should touch > this variable and this function makes sure it uses it properly. Similar > applies to flags which is initialized only if we really take the slow > path (has a meaning only if locked == true). > > So this is not really needed. Was this triggered by a compiler warning? The problem is that you are attempting to read 'locked' when you call mem_cgroup_end_page_stat(), so it gets used even before you enter the function - and using uninitialized variables is undefined. Yes, it's a compiler warning. Thanks, Sasha -- 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>