Re: [patch 12/14] drivers/dmapool: use TASK_UNINTERRUPTIBLE insteadof TASK_INTERRUPTIBLE

[Andrew Morton]

domen@xxxxxxxxxxxx wrote:
>
>  use TASK_UNINTERRUPTIBLE  instead of TASK_INTERRUPTIBLE
> 
>  Signed-off-by: Nishanth Aravamudan <nacc@xxxxxxxxxx>
>  Signed-off-by: Domen Puncer <domen@xxxxxxxxxxxx>
>  ---
> 
> 
>   kj-domen/drivers/base/dmapool.c |    2 +-
>   1 files changed, 1 insertion(+), 1 deletion(-)
> 
>  diff -puN drivers/base/dmapool.c~task_unint-drivers_base_dmapool drivers/base/dmapool.c
>  --- kj/drivers/base/dmapool.c~task_unint-drivers_base_dmapool	2005-03-05 16:11:21.000000000 +0100
>  +++ kj-domen/drivers/base/dmapool.c	2005-03-05 16:11:21.000000000 +0100
>  @@ -293,7 +293,7 @@ restart:
>   		if (mem_flags & __GFP_WAIT) {
>   			DECLARE_WAITQUEUE (wait, current);
>   
>  -			current->state = TASK_INTERRUPTIBLE;
>  +			set_current_state(TASK_UNINTERRUPTIBLE);
>   			add_wait_queue (&pool->waitq, &wait);
>   			spin_unlock_irqrestore (&pool->lock, flags);

This code is alread a bit odd.  If we're prepared to sleep in there, then
why use GFP_ATOMIC?

If it is so that we can dig a bit deeper into the free page pools then
something like __GFP_WAIT|__GFP_HIGH would be preferable.

And why isn't mem_flags passed into pool_alloc_page() verbatim?

I agree on the TASK_UNINTERRUPTIBLE change: if the calling task happens to
have signal_pending() then the schedule_timeout() will fall right through. 
Why should we change kernel memory allocation strategy if the user hit ^C? 

Also, __set_current_state() can be user here: the add_wait_queue() contains
the necessary barriers.  (Grubby, but we do that in quite a few places with
this particular code sequence (we should have an add_wait_queue() variant
which does the add_wait_queue+__set_current_state all in one hit (but let's
not, else I'll be buried in another 1000 cleanuplets))).

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