Re: [PATCH 07/10] mm: warn about vfree from atomic context

[Andrey Ryabinin]

On 11/18/2016 04:03 PM, Christoph Hellwig wrote:
> We can't handle vfree itself from atomic context, but callers
> can explicitly use vfree_atomic instead, which defers the actual
> vfree to a workqueue.  Unfortunately in_atomic does not work
> on non-preemptible kernels, so we can't just do the right thing
> by default.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>  mm/vmalloc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 80f3fae..e2030b4 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1530,6 +1530,7 @@ void vfree_atomic(const void *addr)
>  void vfree(const void *addr)
>  {
>  	BUG_ON(in_nmi());
> +	WARN_ON_ONCE(in_atomic());

This one is wrong. We still can call vfree() from interrupt context.
So WARN_ON_ONCE(in_atomic() && !in_interrupt()) would be correct,
but also redundant. DEBUG_ATOMIC_SLEEP=y should catch illegal vfree() calls.
Let's just drop this patch, ok?



>  	kmemleak_free(addr);
>  
>