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SubjectRe: [PATCH 4/7] mm: defer vmalloc from atomic context
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On 10/22/2016 06:17 PM, Christoph Hellwig wrote:
> We want to be able to use a sleeping lock for freeing vmap to keep
> latency down. For this we need to use the deferred vfree mechanisms
> no only from interrupt, but from any atomic context.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> mm/vmalloc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index a4e2cec..bcc1a64 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1509,7 +1509,7 @@ void vfree(const void *addr)
>
> if (!addr)
> return;
> - if (unlikely(in_interrupt())) {
> + if (unlikely(in_atomic())) {

in_atomic() cannot always detect atomic context, thus it shouldn't be used here.
You can add something like vfree_in_atomic() and use it in atomic call sites.

> struct vfree_deferred *p = this_cpu_ptr(&vfree_deferred);
> if (llist_add((struct llist_node *)addr, &p->list))
> schedule_work(&p->wq);
>

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