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cgroup: avoid false positive gcc-6 warning 

When all subsystems are disabled, gcc notices that cgroup_subsys_enabled_key
is a zero-length array and that any access to it must be out of bounds:

In file included from ../include/linux/cgroup.h:19:0,
                 from ../kernel/cgroup.c:31:
../kernel/cgroup.c: In function 'cgroup_add_cftypes':
../kernel/cgroup.c:261:53: error: array subscript is above array bounds [-Werror=array-bounds]
  return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
                            ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
../include/linux/jump_label.h:271:40: note: in definition of macro 'static_key_enabled'
  static_key_count((struct static_key *)x) > 0;    \
                                        ^

We should never call the function in this particular case, so this is
not a bug. In order to silence the warning, this adds an explicit check
for the CGROUP_SUBSYS_COUNT==0 case.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Arnd Bergmann 2016-03-15 00:21:06 +01:00 committed by Tejun Heo
parent 2b021cbf3c
commit cfe02a8a97
1 changed files with 3 additions and 0 deletions
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3
kernel/cgroup.c
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@ -246,6 +246,9 @@ static int cgroup_addrm_files(struct cgroup_subsys_state *css,
*/ */
static bool cgroup_ssid_enabled(int ssid) static bool cgroup_ssid_enabled(int ssid)
{ {
if (CGROUP_SUBSYS_COUNT == 0)
return false;
return static_key_enabled(cgroup_subsys_enabled_key[ssid]); return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
} }