Re: [PATCH v2] mm: vmscan: abort proactive reclaim early when freezing for suspend

[Oleg Nesterov]

Hi Michal,

On 07/15, Michal Hocko wrote:
>
> Oleg you haven't been CCed from the top of the thread but TL;DR is that
> we need to freeze a user task performing pro-active memory reclaim that
> might take long.  Currently we are calling signal_pending to bail out
> but that leaks EINTR which is bad as freezing task has a side effect of
> terminating it.

Sorry, I guess I don't understand the problem...

Yes, unlike EINTR, ERESTARTSYS should not leak to the caller (just in case,
debugger can see this error code).

But I am sure you know this. And the patch looks fine to me.

Oleg.

> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 35c3bb15ae96..336af76d2a28 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -7909,8 +7909,13 @@ int user_proactive_reclaim(char *buf,
>  		unsigned long batch_size = (nr_to_reclaim - nr_reclaimed) / 4;
>  		unsigned long reclaimed;
>  
> +		/*
> +		 * Make sure that we enter freezer without delaying much and
> +		 * leaking EINTR when that happens but also take care of 
> +		 * fatal signals to terminate.
> +		 */
>  		if (signal_pending(current))
> -			return -EINTR;
> +			return -ERESTARTSYS;
>  
>  		/*
>  		 * This is the final attempt, drain percpu lru caches in the
> -- 
> Michal Hocko
> SUSE Labs
>