Hi Arnd,
On Mon, Jan 25, 2016 at 04:45:50PM +0100, Arnd Bergmann wrote:
> When CONFIG_DEBUG_VM is set, the various VM_BUG_ON() confuse gcc to
> the point where it cannot remember that 'memcg' is known to be initialized:
>
> mm/memcontrol.c: In function 'mem_cgroup_can_attach':
> mm/memcontrol.c:4791:9: warning: 'memcg' may be used uninitialized in this function [-Wmaybe-uninitialized]
>
> On ARM gcc-5.1, the above happens when any two or more of the VM_BUG_ON()
> are active, but not when I remove most or all of them. This is clearly
> random behavior and the only way I've found to shut up the warning is
> to add an explicit initialization.
>
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Thanks Arnd.
This has been fixed upstream already:
commit eed67d75b66748a498a0592d9704081a98509444
Author: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Date: Wed Dec 23 14:53:27 2015 -0700
cgroup: Fix uninitialized variable warning
Commit 1f7dd3e5a6e4 ("cgroup: fix handling of multi-destination migration
from subtree_control enabling") introduced the following compiler warning:
mm/memcontrol.c: In function ‘mem_cgroup_can_attach’:
mm/memcontrol.c:4790:9: warning: ‘memcg’ may be used uninitialized in this function [-Wmaybe-uninitialized]
mc.to = memcg;
^
Fix this by initializing 'memcg' to NULL.
This was found using gcc (GCC) 4.9.2 20150212 (Red Hat 4.9.2-6).
Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
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