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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Ralph Siemsen <ralph.siemsen@linaro.org>
Cc: Peter Chen <peter.chen@kernel.org>, Pawel Laszczak <pawell@cadence.com>,
	Roger Quadros <rogerq@kernel.org>,
	Aswath Govindraju <a-govindraju@ti.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Felipe Balbi <felipe.balbi@linux.intel.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-rt-devel@lists.linux.dev,
	Thomas Gleixner <tglx@linutronix.de>,
	Steven Rostedt <rostedt@goodmis.org>, stable@vger.kernel.org
Subject: Re: [PATCH v2] usb: cdns3: Fix deadlock when using NCM gadget
Message-ID: <20250319055653.uSl-FEiQ@linutronix.de>
References: <20250318-rfs-cdns3-deadlock-v2-1-bfd9cfcee732@linaro.org>
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In-Reply-To: <20250318-rfs-cdns3-deadlock-v2-1-bfd9cfcee732@linaro.org>

On 2025-03-18 11:09:32 [-0400], Ralph Siemsen wrote:
> The cdns3 driver has the same NCM deadlock as fixed in cdnsp by commit
> 58f2fcb3a845 ("usb: cdnsp: Fix deadlock issue during using NCM gadget").
> 
> Under PREEMPT_RT the deadlock can be readily triggered by heavy network
> traffic, for example using "iperf --bidir" over NCM ethernet link.
> 
> The deadlock occurs because the threaded interrupt handler gets
> preempted by a softirq, but both are protected by the same spinlock.
> Prevent deadlock by disabling softirq during threaded irq handler.
> 
> cc: stable@vger.kernel.org
> Fixes: 7733f6c32e36 ("usb: cdns3: Add Cadence USB3 DRD Driver")
> Signed-off-by: Ralph Siemsen <ralph.siemsen@linaro.org>

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Sebastian