netdev - Re: [PATCH net-next] net: Correct wrong BH disable in hard-interrupt.

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Message-ID: <20220223075517.468dec75@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 23 Feb 2022 07:55:17 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Sebastian Andrzej Siewior <sebastian@...akpoint.cc>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        bpf@...r.kernel.org, netdev@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Toke Høiland-Jørgensen 
        <toke@...e.dk>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>
Subject: Re: [PATCH net-next] net: Correct wrong BH disable in
 hard-interrupt.

On Wed, 23 Feb 2022 09:05:43 +0100 Sebastian Andrzej Siewior wrote:
> On 2022-02-16 18:50:46 [+0100], Sebastian Andrzej Siewior wrote:
> > I missed the obvious case where netif_ix() is invoked from hard-IRQ
> > context.
> > 
> > Disabling bottom halves is only needed in process context. This ensures
> > that the code remains on the current CPU and that the soft-interrupts
> > are processed at local_bh_enable() time.
> > In hard- and soft-interrupt context this is already the case and the
> > soft-interrupts will be processed once the context is left (at irq-exit
> > time).
> > 
> > Disable bottom halves if neither hard-interrupts nor soft-interrupts are
> > disabled. Update the kernel-doc, mention that interrupts must be enabled
> > if invoked from process context.
> > 
> > Fixes: baebdf48c3600 ("net: dev: Makes sure netif_rx() can be invoked in any context.")
> > Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>  
> 
> This patch is marked as "Changes Requested" in patchwork. Could someone
> please explain?
> The USB/dwc3 fallout reported by Marek was addressed in 
>    usb: dwc3: gadget: Let the interrupt handler disable bottom halves.
>    https://lore.kernel.org/r/Yg/YPejVQH3KkRVd@linutronix.de
> 
> and is not a shortcoming in this patch but a problem in dwc3 that was
> just noticed.

Unclear, let me apply it now.