Re: [PATCH 2/6] mm: mark all calls into the vmalloc subsystem as potentially sleeping

[Joel Fernandes]

Hi Christoph,

On Wed, Oct 19, 2016 at 9:31 AM, Christoph Hellwig <hch@xxxxxx> wrote:
> On Wed, Oct 19, 2016 at 08:34:40AM -0700, Andy Lutomirski wrote:
>>
>> It would be quite awkward for a task stack to get freed from a
>> sleepable context, because the obvious sleepable context is the task
>> itself, and it still needs its stack.  This was true even in the old
>> regime when task stacks were freed from RCU context.
>>
>> But vfree has a magic automatic deferral mechanism.  Couldn't you make
>> the non-deferred case might_sleep()?
>
> But it's only magic from interrupt context..
>
> Chris, does this patch make virtually mapped stack work for you again?
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index f2481cb..942e02d 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1533,7 +1533,7 @@ void vfree(const void *addr)
>
>         if (!addr)
>                 return;
> -       if (unlikely(in_interrupt())) {
> +       if (in_interrupt() || in_atomic()) {

in_atomic() also checks in_interrupt() cases so only in_atomic() should suffice.

Thanks,

Joel