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Subject: Re: [PATCH] net: stmmac: Don't call _irqoff() with hardirqs enabled
From:   Heiner Kallweit <hkallweit1@gmail.com>
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     John Keeping <john@metanate.com>, netdev@vger.kernel.org,
        Giuseppe Cavallaro <peppe.cavallaro@st.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        Jose Abreu <joabreu@synopsys.com>,
        "David S. Miller" <davem@davemloft.net>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Eric Dumazet <edumazet@google.com>
References: <20201008162749.860521-1-john@metanate.com>
 <8036d473-68bd-7ee7-e2e9-677ff4060bd3@gmail.com>
 <20201009085805.65f9877a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
 <725ba7ca-0818-074b-c380-15abaa5d037b@gmail.com>
Message-ID: <070b2b87-f38c-088d-4aaf-12045dbd92f7@gmail.com>
Date:   Sat, 10 Oct 2020 15:08:15 +0200
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On 09.10.2020 18:06, Heiner Kallweit wrote:
> On 09.10.2020 17:58, Jakub Kicinski wrote:
>> On Fri, 9 Oct 2020 16:54:06 +0200 Heiner Kallweit wrote:
>>> I'm thinking about a __napi_schedule version that disables hard irq's
>>> conditionally, based on variable force_irqthreads, exported by the irq
>>> subsystem. This would allow to behave correctly with threadirqs set,
>>> whilst not loosing the _irqoff benefit with threadirqs unset.
>>> Let me come up with a proposal.
>>
>> I think you'd need to make napi_schedule_irqoff() behave like that,
>> right?  Are there any uses of napi_schedule_irqoff() that are disabling
>> irqs and not just running from an irq handler?
>>
> Right, the best approach depends on the answer to the latter question.
> I didn't check this yet, therefore I described the least intrusive approach.
> 

With some help from coccinelle I identified the following functions that
call napi_schedule_irqoff() or __napi_schedule_irqoff() and do not run
from an irq handler (at least not at the first glance).

dpaa2_caam_fqdan_cb
qede_simd_fp_handler
mlx4_en_rx_irq
mlx4_en_tx_irq
qeth_qdio_poll
netvsc_channel_cb
napi_watchdog