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

[Loktionov, Aleksandr]

> -----Original Message-----
> From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Sent: Thursday, February 5, 2026 11:04 AM
> To: Loktionov, Aleksandr <aleksandr.loktionov@xxxxxxxxx>
> Cc: Kurt Kanzenbach <kurt@xxxxxxxxxxxxx>; Nguyen, Anthony L
> <anthony.l.nguyen@xxxxxxxxx>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@xxxxxxxxx>; Paul Menzel <pmenzel@xxxxxxxxxxxxx>;
> Vadim Fedorenko <vadim.fedorenko@xxxxxxxxx>; Gomes, Vinicius
> <vinicius.gomes@xxxxxxxxx>; netdev@xxxxxxxxxxxxxxx; Richard Cochran
> <richardcochran@xxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Andrew Lunn
> <andrew+netdev@xxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; intel-
> wired-lan@xxxxxxxxxxxxxxxx; Keller, Jacob E
> <jacob.e.keller@xxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Paolo
> Abeni <pabeni@xxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>
> Subject: Re: RE: [Intel-wired-lan] [PATCH iwl-next v3] igb: Retrieve
> Tx timestamp directly from interrupt for i210
> 
> On 2026-02-05 09:47:14 [+0000], Loktionov, Aleksandr wrote:
> …
> > > --- a/drivers/net/ethernet/intel/igb/igb_ptp.c
> > > +++ b/drivers/net/ethernet/intel/igb/igb_ptp.c
> > > @@ -796,6 +796,28 @@ static int igb_ptp_verify_pin(struct
> …
> > > +	igb_ptp_tx_hwtstamp(adapter); <-Calls existing function
> designed for work queue!
> >
> > skb_tstamp_tx() can sleep
> > Smells like sleep-in-atomic isn't it?
> 
> 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 

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