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SubjectRe: [PATCH] Make kthread_stop() not oops when passed a bad pointer
On Tue, 5 Aug 2008 07:55:59 -0600 Matthew Wilcox <matthew@wil.cx> wrote:

>
> Due to some botched error handling code in a driver I was writing, I
> recently called kthread_stop(NULL). It's terribly exciting to discover
> that you've just oopsed while holding a mutex that's required in order
> to shut down. Make kthread_stop a little more robust against numbskulls
> like me.
>
> Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
>
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 96cff2f..06c3477 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -201,6 +201,9 @@ int kthread_stop(struct task_struct *k)
> {
> int ret;
>
> + if (!k || IS_ERR(k))
> + return -EINVAL;
> +
> mutex_lock(&kthread_stop_lock);
>

hrm.

a) as this is a programming error, the programmer would like it not
to be hidden. A WARN_ON() would address that.

b) there are many instances of

if (p)
kthread_stop(p);

which could now be simplified to

kthread_stop(p);

c) a) and b) are incompatible.


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