Re: [PATCH v3] pvcalls-front: Avoid __get_free_pages(GFP_KERNEL) under spinlock

[Juergen Gross]

On 30/11/2018 12:01, Wen Yang wrote:
> The problem is that we call this with a spin lock held.
> The call tree is:
> pvcalls_front_accept() holds bedata->socket_lock.
>     -> create_active()
>         -> __get_free_pages() uses GFP_KERNEL
> 
> The create_active() function is only called from pvcalls_front_accept()
> with a spin_lock held, The allocation is not allowed to sleep and
> GFP_KERNEL is not sufficient.
> 
> This issue was detected by using the Coccinelle software.
> 
> v2: Add a function doing the allocations which is called
>     outside the lock and passing the allocated data to
>     create_active().
> v3: Use the matching deallocators i.e., free_page()
>     and free_pages(), respectively.
> 
> Suggested-by: Juergen Gross <jgross@xxxxxxxx>
> Signed-off-by: Wen Yang <wen.yang99@xxxxxxxxxx>
> CC: Julia Lawall <julia.lawall@xxxxxxx>
> CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> CC: Juergen Gross <jgross@xxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: xen-devel@xxxxxxxxxxxxxxxxxxxx
> CC: linux-kernel@xxxxxxxxxxxxxxx
> ---

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Juergen