linux-kernel - Re: [PATCH v12 01/10] i915: only initialize struct ref_tracker

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Message-ID: <bcc3aaschdk64nieucfllygsqjvtvpffgxf7mjamabkeofangr@tmbkssauvg2d>
Date: Fri, 30 May 2025 11:01:18 +0000
From: Krzysztof Karas <krzysztof.karas@...el.com>
To: Jeff Layton <jlayton@...nel.org>
CC: Andrew Morton <akpm@...ux-foundation.org>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
	<horms@...nel.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, "Jani
 Nikula" <jani.nikula@...ux.intel.com>, Joonas Lahtinen
	<joonas.lahtinen@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>, Kuniyuki Iwashima <kuniyu@...zon.com>,
	Qasim Ijaz <qasdev00@...il.com>, Nathan Chancellor <nathan@...nel.org>,
	Andrew Lunn <andrew@...n.ch>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
	<intel-gfx@...ts.freedesktop.org>
Subject: Re: [PATCH v12 01/10] i915: only initialize struct ref_tracker_dir
 once

Hi Jeff,

> I got some warnings from the i915 CI with the ref_tracker debugfs
> patches applied, that indicated that these ref_tracker_dir_init() calls
> were being called more than once. If references were held on these
> objects between the initializations, then that could lead to leaked ref
> tracking objects.
> 
> Since these objects are zalloc'ed, ensure that they are only initialized
> once by testing whether the first byte of the name field is 0.

Are you referring to these warnings?
<3> [314.043410] debugfs: File 'intel_wakeref@...f88815111a308' in directory 'ref_tracker' already present!
<4> [314.043427] ref_tracker: ref_tracker: unable to create debugfs file for intel_wakeref@...f88815111a308: -EEXIST

I think those might be caused by introduction of:
"ref_tracker: automatically register a file in debugfs for a ref_tracker_dir".

Current version of "ref_tracker: add a static classname string
to each ref_tracker_dir" further in this series should prevent
multiple calls to "ref_tracker_dir_init()", so this patch could
be dropped I think.
If my reasoning is wrong however, then please add a note to the
commit message which explains why this is needed in more detail
or/and move this patch right before it is necessary. Otherwise
it looks like a vague workaround.

Best Regards,
Krzysztof