linux-kernel - Re: RE: RE: [Intel-wired-lan] [PATCH iwl-next v3] igb: Retrieve Tx timestamp directly from interrupt for i210

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Message-ID: <20260205105238.e8F64peo@linutronix.de>
Date: Thu, 5 Feb 2026 11:52:38 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
Cc: Kurt Kanzenbach <kurt@...utronix.de>,
	"Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
	"Kitszel, Przemyslaw" <przemyslaw.kitszel@...el.com>,
	Paul Menzel <pmenzel@...gen.mpg.de>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	"Gomes, Vinicius" <vinicius.gomes@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Richard Cochran <richardcochran@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Eric Dumazet <edumazet@...gle.com>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"Keller, Jacob E" <jacob.e.keller@...el.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: RE: RE: [Intel-wired-lan] [PATCH iwl-next v3] igb: Retrieve Tx
 timestamp directly from interrupt for i210

On 2026-02-05 10:37:05 [+0000], Loktionov, Aleksandr wrote:
> > 
> > How or where can it sleep?
> > 
> > Sebastian
> 
> igb_ptp_tx_hwtstamp() -> https://elixir.bootlin.com/linux/v6.19-rc5/C/ident/skb_tstamp_tx -> https://elixir.bootlin.com/linux/v6.19-rc5/C/ident/__skb_complete_tx_timestamp -> https://elixir.bootlin.com/linux/v6.19-rc5/C/ident/sock_queue_err_skb -> https://elixir.bootlin.com/linux/v6.19-rc5/C/ident/skb_queue_tail -> https://elixir.bootlin.com/linux/v6.19-rc5/source/net/core/skbuff.c#L4075 

Would you please quote an actual call chain that can be looked up and
not this where a line crosses 300 characters?

> spin_lock_irqsave(&wq_head->lock, flags);  <- RT mutex can sleep

Okay. So you are concerned about this spinlock_t, I see.
igb_tsync_interrupt() also invokes ptp_clock_event() which acquires
pps_event_time::tsevqs_lock. Why is this not a problem?

Sebastian