From: Nam Cao <namcao@linutronix.de>
To: "Holger Hoffstätte" <holger@applied-asynchrony.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
John Ogness <john.ogness@linutronix.de>,
Clark Williams <clrkwllms@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-rt-devel@lists.linux.dev, linux-rt-users@vger.kernel.org,
Joe Damato <jdamato@fastly.com>,
Martin Karsten <mkarsten@uwaterloo.ca>,
Jens Axboe <axboe@kernel.dk>,
Frederic Weisbecker <frederic@kernel.org>,
Valentin Schneider <vschneid@redhat.com>
Subject: Re: [PATCH v2] eventpoll: Fix priority inversion problem
Date: Wed, 28 May 2025 08:12:52 +0200 [thread overview]
Message-ID: <20250528061252.AeDA23yH@linutronix.de> (raw)
In-Reply-To: <3475f3f1-4109-b6ac-6ea6-dadcdec8db1f@applied-asynchrony.com>
On Wed, May 28, 2025 at 07:57:26AM +0200, Holger Hoffstätte wrote:
> I have been running with v2 on 6.15.0 without any issues so far, but just
> found this in my server's kern.log:
Thanks for testing!
> It seems the condition (!n) in __ep_remove is not always true and the WARN_ON triggers.
> This is the first and only time I've seen this. Currently rebuilding with v3.
Yeah this means __ep_remove() thinks the item is in epoll's rdllist and
attempt to remove it, but then couldn't actually find the item in the list.
__ep_remove() relies on the 'ready' flag, and this flags is quite
complicated. And as my colleague pointed out off-list, I got memory
ordering wrong for this flag. Therefore it is likely that you stepped on a
bug with this flag.
I got rid of this flag in v3, so hopefully the problem goes away.
Best regards,
Nam
next prev parent reply other threads:[~2025-05-28 6:12 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-23 6:11 [PATCH v2] eventpoll: Fix priority inversion problem Nam Cao
2025-05-23 12:26 ` Sebastian Andrzej Siewior
2025-05-26 5:39 ` Nam Cao
2025-05-23 14:31 ` Sebastian Andrzej Siewior
2025-05-28 5:57 ` Holger Hoffstätte
2025-05-28 6:07 ` Holger Hoffstätte
2025-05-28 6:12 ` Nam Cao [this message]
2025-05-28 8:04 ` Nam Cao
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