linux-kernel - Re: [RFC PATCH] mm: silence soft lockups from unlock

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Message-ID: <20200721141749.GA742741@chrisdown.name>
Date:   Tue, 21 Jul 2020 15:17:49 +0100
From:   Chris Down <chris@...isdown.name>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [RFC PATCH] mm: silence soft lockups from unlock_page

I understand the pragmatic considerations here, but I'm quite concerned about 
the maintainability and long-term ability to reason about a patch like this.  
For example, how do we know when this patch is safe to remove? Also, what other 
precedent does this set for us covering for poor userspace behaviour?

Speaking as a systemd maintainer, if udev could be doing something better on 
these machines, we'd be more than receptive to help fix it. In general I am 
against explicit watchdog tweaking here because a.) there's potential to mask 
other problems, and b.) it seems like the kind of one-off trivia nobody is 
going to remember exists when doing complex debugging in future.

Is there anything preventing this being remedied in udev, instead of the 
kernel?