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Date: Sun, 14 Jan 2024 18:59:19 +0200
From: Andy Shevchenko <andriy.shevchenko@intel.com>
To: Hardik Gajjar <hgajjar@de.adit-jv.com>,
	Ferry Toth <ftoth@exalondelft.nl>
Cc: gregkh@linuxfoundation.org, s.hauer@pengutronix.de,
	jonathanh@nvidia.com, linux-usb@vger.kernel.org,
	linux-kernel@vger.kernel.org, quic_linyyuan@quicinc.com,
	paul@crapouillou.net, quic_eserrao@quicinc.com,
	erosca@de.adit-jv.com
Subject: Re: [PATCH v4] usb: gadget: u_ether: Replace netif_stop_queue with
 netif_device_detach
Message-ID: <ZaQS5x-XK08Jre6I@smile.fi.intel.com>
References: <20231006153808.9758-1-hgajjar@de.adit-jv.com>
 <20231006155646.12938-1-hgajjar@de.adit-jv.com>
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

+Cc: Ferry.

On Fri, Oct 06, 2023 at 05:56:46PM +0200, Hardik Gajjar wrote:
> This patch replaces the usage of netif_stop_queue with netif_device_detach
> in the u_ether driver. The netif_device_detach function not only stops all
> tx queues by calling netif_tx_stop_all_queues but also marks the device as
> removed by clearing the __LINK_STATE_PRESENT bit.
> 
> This change helps notify user space about the disconnection of the device
> more effectively, compared to netif_stop_queue, which only stops a single
> transmit queue.

This change effectively broke my USB ether setup.

git bisect start
# status: waiting for both good and bad commits
# good: [1f24458a1071f006e3f7449c08ae0f12af493923] Merge tag 'tty-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
git bisect good 1f24458a1071f006e3f7449c08ae0f12af493923
# status: waiting for bad commit, 1 good commit known
# bad: [2c40c1c6adab90ee4660caf03722b3a3ec67767b] Merge tag 'usb-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
git bisect bad 2c40c1c6adab90ee4660caf03722b3a3ec67767b
# bad: [17d6b82d2d6d467149874b883cdba844844b996d] usb/usbip: fix wrong data added to platform device
git bisect bad 17d6b82d2d6d467149874b883cdba844844b996d
# good: [ba6b83a910b6d8a9379bda55cbf06cb945473a96] usb: xhci-mtk: add a bandwidth budget table
git bisect good ba6b83a910b6d8a9379bda55cbf06cb945473a96
# good: [dddc00f255415b826190cfbaa5d6dbc87cd9ded1] Revert "usb: gadget: uvc: cleanup request when not in correct state"
git bisect good dddc00f255415b826190cfbaa5d6dbc87cd9ded1
# bad: [8f999ce60ea3d47886b042ef1f22bb184b6e9c59] USB: typec: tps6598x: Refactor tps6598x port registration
git bisect bad 8f999ce60ea3d47886b042ef1f22bb184b6e9c59
# bad: [f49449fbc21e7e9550a5203902d69c8ae7dfd918] usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach
git bisect bad f49449fbc21e7e9550a5203902d69c8ae7dfd918
# good: [97475763484245916735a1aa9a3310a01d46b008] USB: usbip: fix stub_dev hub disconnect
git bisect good 97475763484245916735a1aa9a3310a01d46b008
# good: [0f5aa1b01263b8b621bc4f031a1f2983ef8517b7] usb: usbtest: fix a type promotion bug
git bisect good 0f5aa1b01263b8b621bc4f031a1f2983ef8517b7
# first bad commit: [f49449fbc21e7e9550a5203902d69c8ae7dfd918] usb: gadget: u_ether: Replace netif_stop_queue with netif_device_detach

Note, revert indeed helps. Should I send a revert?

I use configfs to setup USB EEM function and it worked till this commit.
If needed, I can share my scripts, but I believe it's not needed as here
we see a clear regression.

-- 
With Best Regards,
Andy Shevchenko