netdev - Re: [PATCH] rhashtable: Fix potential deadlock by moving schedule

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Message-ID: <20250110-diligent-woodpecker-of-promotion-3cbcb1@leitao>
Date: Fri, 10 Jan 2025 01:49:44 -0800
From: Breno Leitao <leitao@...ian.org>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: Michael Kelley <mhklinux@...look.com>,
	"saeedm@...dia.com" <saeedm@...dia.com>,
	"tariqt@...dia.com" <tariqt@...dia.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Graf <tgraf@...g.ch>, Tejun Heo <tj@...nel.org>,
	Hao Luo <haoluo@...gle.com>, Josh Don <joshdon@...gle.com>,
	Barret Rhoden <brho@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rhashtable: Fix potential deadlock by moving
 schedule_work outside lock

Hello Herbet,

On Fri, Jan 10, 2025 at 05:27:49PM +0800, Herbert Xu wrote:

> Sorry, I think it was my addition that broke things.  The condition
> for checking whether an entry is inserted is incorrect, thus resulting
> in an underflow of the number of entries after entry removal.

That is what I though originally as well, but I was not convinced. While
reading the code, I understood that, if new_tbl is not NULL, then
PTR_ERR(data) will be -ENOENT.

In which case `net_tbl` will not be NULL, and PTR_ERR(data) != -ENOENT?

Thanks for solving it.

> Please test this patch:

I don't have an easy reproducer yet, but, I will get this patch in ~50
hosts and see if any of them misbehave during the weekend.

Misbehaving in my case is strongly associate with messages like the
following being printed:

	kobject_uevent: unable to create netlink socket!


Thanks
--breno