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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: "Jiangong.Han" <jiangong.han@windriver.com>, gregkh@linuxfoundation.org,
	surban@surban.net, eeodqql09@gmail.com, kees@kernel.org,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] usb: gadget: dummy_hcd: fix IRQs-disabled violation in
 dummy_timer()
Message-ID: <20260717083423.NViVto15@linutronix.de>
References: <20260716020713.1698421-1-jiangong.han@windriver.com>
 <17c672c6-bac3-456a-895f-d5406624a3fd@rowland.harvard.edu>
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In-Reply-To: <17c672c6-bac3-456a-895f-d5406624a3fd@rowland.harvard.edu>

On 2026-07-15 22:15:52 [-0400], Alan Stern wrote:
> This is not the right way to solve the problem observed in carl9170.  It 
> is documented that usb_hcd_giveback_urb() runs in atomic context, and 
> drivers' completion handlers should not expect to be called with 
> interrupts enabled.  The problem lies in carl9170_get_queued_skb(); 
> that's where it needs to be fixed.

I guess we don't see this that often because the widely used HCDs have
HCD_BH set.
I sort of think that we already did have this conversation about
having unlock+lock with irq and not skipping it. But yes, while this
would solve the problem _here_ we would still have the same warning on
OHCI.

Take a look at other drivers in drivers/net/usb/, they delay their doing
to napi/ workqueue/ tasklet.

> Alan Stern

Sebastian