linux-kernel - Re: [PATCH v2] ptp: remove ptp->n_vclocks check logic in ptp_vclock_in

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Message-ID: <aC8ZT3MW2EhPSQGK@hoboy.vegasvil.org>
Date: Thu, 22 May 2025 05:32:15 -0700
From: Richard Cochran <richardcochran@...il.com>
To: Jeongjun Park <aha310510@...il.com>
Cc: andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, yangbo.lu@....com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ptp: remove ptp->n_vclocks check logic in
 ptp_vclock_in_use()

On Wed, May 21, 2025 at 01:07:17AM +0900, Jeongjun Park wrote:
> There is no disagreement that we should check both ptp->is_virtual_clock
> and ptp->n_vclocks to check if the ptp virtual clock is in use.
> 
> However, when we acquire ptp->n_vclocks_mux to read ptp->n_vclocks in
> ptp_vclock_in_use(), we observe a recursive lock in the call trace
> starting from n_vclocks_store().

> The best way to solve this is to remove the logic that checks
> ptp->n_vclocks in ptp_vclock_in_use().

Acked-by: Richard Cochran <richardcochran@...il.com>