linux-kernel - Re: [PATCH v2] sched/all: Change all BUG_ON() instances in the scheduler to WARN_ON

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Message-ID: <cbb3697c-f310-ae91-1322-fea5794ebf30@nvidia.com>
Date:   Mon, 15 Aug 2022 15:12:19 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Mel Gorman <mgorman@...e.de>, Ingo Molnar <mingo@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Peter Xu <peterx@...hat.com>, Hugh Dickins <hughd@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Jason Gunthorpe <jgg@...dia.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v2] sched/all: Change all BUG_ON() instances in the
 scheduler to WARN_ON_ONCE()

On 8/15/22 07:41, Mel Gorman wrote:
> For the rest, I didn't see obvious recovery paths that would allow the
> system to run predictably. Any of them firing will have unpredictable
> consequences (e.g. move_queued_task firing would be fun if it was a per-cpu
> kthread). Depending on which warning triggers, the remaining life of the
> system may be very short but maybe long enough to be logged even if system
> locks up shortly afterwards.

Hi Mel,

Are you basically saying, "WARN_ON*() seems acceptable in mm/, because
we can at least get the problem logged before it locks up, probably"?

Or are you implying that we should instead introduce and use some new
PANIC_ON() or VM_PANIC_ON() set of macros that would allow proper "log
then reboot" behavior?


thanks,
-- 
John Hubbard
NVIDIA