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Date: Tue, 24 Feb 2026 15:54:32 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Siddharth Vadapalli <s-vadapalli@ti.com>
Cc: <andrew+netdev@lunn.ch>, <davem@davemloft.net>, <edumazet@google.com>,
 <pabeni@redhat.com>, <danishanwar@ti.com>, <rogerq@kernel.org>,
 <horms@kernel.org>, <mwalle@kernel.org>, <nm@ti.com>, <v-singh1@ti.com>,
 <vadim.fedorenko@linux.dev>, <matthias.schiffer@ew.tq-group.com>,
 <vigneshr@ti.com>, <m-malladi@ti.com>, <jacob.e.keller@intel.com>,
 <stable@vger.kernel.org>, <netdev@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
 <srk@ti.com>
Subject: Re: [PATCH net 1/3] net: ethernet: ti: am65-cpsw-nuss: set
 irq_disabled after disabling RX IRQ
Message-ID: <20260224155432.15ded392@kernel.org>
In-Reply-To: <c9b1c5c2c5f9587c31132586fddb1921ff6824a8.camel@ti.com>
References: <20260220041431.372610-1-s-vadapalli@ti.com>
	<20260220041431.372610-2-s-vadapalli@ti.com>
	<20260223184803.739c17a7@kernel.org>
	<c9b1c5c2c5f9587c31132586fddb1921ff6824a8.camel@ti.com>
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On Tue, 24 Feb 2026 10:40:05 +0530 Siddharth Vadapalli wrote:
> CPU1 sees irq_disabled being 'true' and before it updates it to 'false', if
> CPU2 also sees irq_disabled
> being 'true', both CPU1 and CPU2 will enter the IF-condition and eventually
> invoke enable_irq().

I think the races are just between NAPI and the HARD IRQ context.
There can only be one NAPI scheduled for a queue, I assume.

> Please let me know if this is what you were referring to. I will use atomic
> APIs at all places to update
> 'irq_disabled'.

I recommend a spin lock, unless you can measure as significant
difference. Locks and atomics have similar cost on many CPUs.
And juggling local state, IRQ state, and NAPI state atomically
will get tricky.