netdev - Re: [PATCH net-next] bnxt_en: replace PTP spinlock with seqlock

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Message-ID: <20241015084157.2f0a2178@kernel.org>
Date: Tue, 15 Oct 2024 08:41:57 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
Cc: Michael Chan <michael.chan@...adcom.com>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] bnxt_en: replace PTP spinlock with seqlock

On Tue, 15 Oct 2024 11:25:00 +0100 Vadim Fedorenko wrote:
> > I think when you adjtime / adjfine (IOW on all the write path) you still
> > need the spin lock. But in addition also the seq lock. And then the
> > read path can take just the seq lock.  
> 
> I think there is a spinlock in seqlock_t which is used to prevent
> multiple writers.

My bad.

> > This will also remove any uncertainty about the bit ops.  
> 
> Should I use read_seqlock_excl_bh()/write_seqlock_bh() for the bit ops
> then?

Yup, modulo what Micheal said in the other leg of the thread, but SGTM.