From: Nick Desaulniers <nick.desaulniers@gmail.com>
To: tj@kernel.org
Cc: Nick Desaulniers <nick.desaulniers@gmail.com>,
Li Zefan <lizefan@huawei.com>,
Johannes Weiner <hannes@cmpxchg.org>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] cgroup: reorder flexible array members of struct cgroup_root
Date: Mon, 16 Oct 2017 23:33:21 -0700 [thread overview]
Message-ID: <20171017063322.11455-1-nick.desaulniers@gmail.com> (raw)
When compiling arch/x86/boot/compressed/eboot.c with HOSTCC=clang, the
following warning is observed:
./include/linux/cgroup-defs.h:391:16: warning: field 'cgrp' with
variable sized type 'struct cgroup' not at the end of a struct or class
is a GNU extension [-Wgnu-variable-sized-type-not-at-end]
struct cgroup cgrp;
^
Flexible array members are a C99 feature, but must be the last member of
a struct. Structs with flexible members composed in other structs must
also be the final members, unless using GNU C extensions.
struct cgroup_root's member cgrp is a struct cgroup, struct cgroup's
member ancestor_ids is a flexible member.
Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
---
Alternatively, we could:
* Not use flexible array members. The flexible array members and allocation
strategy, added in commit b11cfb5807e30 mentions the hot path, so this is
likely not an option?
* Disable this warning for HOSTCC==clang. I'd rather not, since there's
nothing really requiring the use of this particular GNU C extension here,
or specific location of the member cgrp within struct cgroup_root AFAICT.
include/linux/cgroup-defs.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index ade4a78a54c2..2ef256932bf3 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -387,9 +387,6 @@ struct cgroup_root {
/* Unique id for this hierarchy. */
int hierarchy_id;
- /* The root cgroup. Root is destroyed on its release. */
- struct cgroup cgrp;
-
/* for cgrp->ancestor_ids[0] */
int cgrp_ancestor_id_storage;
@@ -410,6 +407,9 @@ struct cgroup_root {
/* The name for this hierarchy - may be empty */
char name[MAX_CGROUP_ROOT_NAMELEN];
+
+ /* The root cgroup. Root is destroyed on its release. */
+ struct cgroup cgrp;
};
/*
--
2.11.0
next reply other threads:[~2017-10-17 6:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-17 6:33 Nick Desaulniers [this message]
2017-10-17 6:40 ` [PATCH] cgroup: reorder flexible array members of struct cgroup_root Nick Desaulniers
2017-10-17 6:45 ` Nick Desaulniers
2017-10-18 13:30 ` Tejun Heo
2017-10-20 7:15 ` Nick Desaulniers
2017-10-21 15:32 ` Tejun Heo
2017-10-21 15:59 ` Aleksa Sarai
2017-10-21 16:03 ` Tejun Heo
2017-10-21 19:08 ` Nick Desaulniers
2017-10-25 21:54 ` Matthias Kaehlcke
2017-10-26 14:32 ` Tejun Heo
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