linux-kernel - Re: [PATCH] hung_task: Skip hung task detection during core dump operations

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Message-Id: <20250813150155.81680178704c4652fd454a80@linux-foundation.org>
Date: Wed, 13 Aug 2025 15:01:55 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: "Nanji Parmar (he/him)" <nparmar@...estorage.com>
Cc: lance.yang@...ux.dev, mhiramat@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hung_task: Skip hung task detection during core dump
 operations

On Wed, 13 Aug 2025 11:30:36 -0700 "Nanji Parmar (he/him)" <nparmar@...estorage.com> wrote:

> Tasks involved in core dump operations can legitimately block for
> extended periods, especially for large memory processes. The hung
> task detector should skip tasks with PF_DUMPCORE (main dumping
> thread) or PF_POSTCOREDUMP (other threads in the group) flags to
> avoid false positive warnings.
> 
> This prevents incorrect hung task reports during legitimate core
> dump generation that can take xx minutes for large processes.

It isn't pleasing to be putting coredump special cases into the core of
the hung-task detector.  Perhaps the hung task detector should get an
equivalent to touch_softlockup_watchdog().  I'm surprised it doesn't
already have such a thing.  Maybe it does and I've forgotten where it is.

Please provide a full description of the problem, mainly the relevant
dmesg output.  Please always provide this full description when
addressing kernel issues, thanks.