[PATCH] cgroup: Initialize root in cgroup_mount

[PATCH] cgroup: Initialize root in cgroup_mount

[Jason Low]

Compiling kernel/ causes warnings:

    ... ‘root’ may be used uninitialized in this function
    ... ‘root’ was declared here

This isn't an issue since there is already logic to not use
root if we goto out_unlock without setting root.

Explicitly initialize root to NULL to suppress this so that we can
focus on catching warnings that can potentially cause bigger issues.

Signed-off-by: Jason Low <jason.low2@hp.com>
---
 kernel/cgroup.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index bb263d0..66684f3 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1738,8 +1738,8 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 			 void *data)
 {
 	struct super_block *pinned_sb = NULL;
+	struct cgroup_root *root = NULL;
 	struct cgroup_subsys *ss;
-	struct cgroup_root *root;
 	struct cgroup_sb_opts opts;
 	struct dentry *dentry;
 	int ret;
-- 
1.7.1

Re: [PATCH] cgroup: Initialize root in cgroup_mount

[Tejun Heo]

On Mon, Jan 26, 2015 at 04:21:39PM -0800, Jason Low wrote:
> Compiling kernel/ causes warnings:
> 
>     ... ‘root’ may be used uninitialized in this function
>     ... ‘root’ was declared here
> 
> This isn't an issue since there is already logic to not use
> root if we goto out_unlock without setting root.
> 
> Explicitly initialize root to NULL to suppress this so that we can
> focus on catching warnings that can potentially cause bigger issues.

Which complier are you using?  The variable, AFAICS, is always set
before being deref'd and the function hasn't triggered spurious
warnings for quite a while with differing versions of gcc.

Thanks.

-- 
tejun

Re: [PATCH] cgroup: Initialize root in cgroup_mount

[Jason Low]

On Tue, 2015-01-27 at 11:10 -0500, Tejun Heo wrote:
> On Mon, Jan 26, 2015 at 04:21:39PM -0800, Jason Low wrote:
> > Compiling kernel/ causes warnings:
> > 
> >     ... ‘root’ may be used uninitialized in this function
> >     ... ‘root’ was declared here
> > 
> > This isn't an issue since there is already logic to not use
> > root if we goto out_unlock without setting root.
> > 
> > Explicitly initialize root to NULL to suppress this so that we can
> > focus on catching warnings that can potentially cause bigger issues.
> 
> Which complier are you using?

Hi Tejun, one of the versions I am seeing this on is gcc 4.6.3.

>   The variable, AFAICS, is always set
> before being deref'd and the function hasn't triggered spurious
> warnings for quite a while with differing versions of gcc.

Re: [PATCH] cgroup: Initialize root in cgroup_mount

[Tejun Heo]

On Tue, Jan 27, 2015 at 09:46:36AM -0800, Jason Low wrote:
> On Tue, 2015-01-27 at 11:10 -0500, Tejun Heo wrote:
> > On Mon, Jan 26, 2015 at 04:21:39PM -0800, Jason Low wrote:
> > > Compiling kernel/ causes warnings:
> > > 
> > >     ... ‘root’ may be used uninitialized in this function
> > >     ... ‘root’ was declared here
> > > 
> > > This isn't an issue since there is already logic to not use
> > > root if we goto out_unlock without setting root.
> > > 
> > > Explicitly initialize root to NULL to suppress this so that we can
> > > focus on catching warnings that can potentially cause bigger issues.
> > 
> > Which complier are you using?
> 
> Hi Tejun, one of the versions I am seeing this on is gcc 4.6.3.

Can you plesae try something newer?  gcc for a while had trouble with
these spurious warnings.  4.6.2 is 3+ years old now.

Thanks.

-- 
tejun