Re: [PATCH] OOM: initialise points variable in out_of_memory()

Re: [PATCH] OOM: initialise points variable in out_of_memory()

[Kurt Garloff]

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Hi Carlos,

On Mon, Feb 27, 2006 at 10:36:25PM +0100, Carlos Martin wrote:
> We didn't initialise points, so the value reported was completely
> random. This doesn't affect the behaviour of the funcion.

Did you observe it?

In the original patch, there is 
+static struct task_struct * select_bad_process(unsigned long *ppoints)
 {
-       unsigned long maxpoints = 0;
        struct task_struct *g, *p;
        struct task_struct *chosen = NULL;
        struct timespec uptime;
+       *ppoints = 0;

And this is called from out_of_memory().

But the constrained_alloc stuff seems to use points before 
select_bad_process() is called, so initializing to 0 is a
good idea. I don't remember having see the constrained_alloc
stuff, though, so I either did not look carefully enough or a 
merge error happened afterwards. 

Thanks for noticing and thanks for sending the fix!

Best,
-- 
Kurt Garloff, Head Architect Linux, Novell Inc.

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Re: [PATCH] OOM: initialise points variable in out_of_memory()

[Carlos Martín]

On Tuesday 28 February 2006 13:13, Kurt Garloff wrote:
> Hi Carlos,
> 
> On Mon, Feb 27, 2006 at 10:36:25PM +0100, Carlos Martin wrote:
> > We didn't initialise points, so the value reported was completely
> > random. This doesn't affect the behaviour of the funcion.
> 
> Did you observe it?

No. GCC complained about it.

> 
> In the original patch, there is 
> +static struct task_struct * select_bad_process(unsigned long *ppoints)
>  {
> -       unsigned long maxpoints = 0;
>         struct task_struct *g, *p;
>         struct task_struct *chosen = NULL;
>         struct timespec uptime;
> +       *ppoints = 0;
> 
> And this is called from out_of_memory().
> 
> But the constrained_alloc stuff seems to use points before 
> select_bad_process() is called, so initializing to 0 is a
> good idea. I don't remember having see the constrained_alloc
> stuff, though, so I either did not look carefully enough or a 
> merge error happened afterwards. 

It never used to be a problem because it was initialised when calling 
select_bad_process().

I though it was your change, but I've looked again and it was Christoph 
Lameter's commit 9b0f8b040acd8dfd23860754c0d09ff4f44e2cbc which introduced 
the problem.

   cmn
-- 
Carlos Martín Nieto    |   http://www.cmartin.tk
Hobbyist programmer    |