linux-kernel - Re: [PATCH v1 1/5] mm/memory_hotplug: check for fatal signals only in offline

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Date:   Tue, 27 Jun 2023 14:34:57 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        virtualization@...ts.linux-foundation.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Oscar Salvador <osalvador@...e.de>,
        Jason Wang <jasowang@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH v1 1/5] mm/memory_hotplug: check for fatal signals only
 in offline_pages()

On Tue 27-06-23 13:22:16, David Hildenbrand wrote:
> Let's check for fatal signals only. That looks cleaner and still keeps
> the documented use case for manual user-space triggered memory offlining
> working. From Documentation/admin-guide/mm/memory-hotplug.rst:
> 
> 	% timeout $TIMEOUT offline_block | failure_handling
> 
> In fact, we even document there: "the offlining context can be terminated
> by sending a fatal signal".

We should be fixing documentation instead. This could break users who do
have a SIGALRM signal hander installed.

> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  mm/memory_hotplug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 8e0fa209d533..0d2151df4ee1 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1879,7 +1879,7 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages,
>  	do {
>  		pfn = start_pfn;
>  		do {
> -			if (signal_pending(current)) {
> +			if (fatal_signal_pending(current)) {
>  				ret = -EINTR;
>  				reason = "signal backoff";
>  				goto failed_removal_isolated;
> -- 
> 2.40.1

-- 
Michal Hocko
SUSE Labs