linux-kernel - Re: [PATCH v2] mm/page_alloc: bail out on fatal signal during reclaim/compaction retry attempt

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Message-ID: <20210519194829.sess6lhfzlmccpdu@ava.usersys.com>
Date:   Wed, 19 May 2021 20:48:29 +0100
From:   Aaron Tomlin <atomlin@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org, vbabka@...e.cz,
        mhocko@...e.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/page_alloc: bail out on fatal signal during
 reclaim/compaction retry attempt

On Wed 2021-05-19 20:32 +0100, Matthew Wilcox wrote:
> On Wed, May 19, 2021 at 08:23:21PM +0100, Aaron Tomlin wrote:
> > +++ b/mm/page_alloc.c
> > @@ -4252,6 +4252,9 @@ should_compact_retry(struct alloc_context *ac, int order, int alloc_flags,
> >  	if (!order)
> >  		return false;
> >  
> > +	if (fatal_signal_pending(current))
> > +		goto out;
> 
> I think 'goto out' will be confusing.  It'll output a tracepoint, which
> isn't going to record that a fatal signal is pending, so it'll cause
> some head scratching for someone looking through the traces.  I
> think we should just return false here and skip the tracepoint.

I agree. Having said this, I do plan to send a patch to illustrate why
compaction should not retry to avoid possible confusion. Nevertheless, I am
happy to modify as per your request.


Kind regards,

-- 
Aaron Tomlin