linux-kernel - Re: [PATCH V2 net 1/3] net: hibmcge: fix rtnl deadlock issue

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Message-ID: <20250805090320.GU8494@horms.kernel.org>
Date: Tue, 5 Aug 2025 10:03:20 +0100
From: Simon Horman <horms@...nel.org>
To: Jijie Shao <shaojijie@...wei.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, andrew+netdev@...n.ch, shenjian15@...wei.com,
	liuyonglong@...wei.com, chenhao418@...wei.com,
	jonathan.cameron@...wei.com, shameerali.kolothum.thodi@...wei.com,
	salil.mehta@...wei.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 net 1/3] net: hibmcge: fix rtnl deadlock issue

On Sat, Aug 02, 2025 at 08:32:24PM +0800, Jijie Shao wrote:
> Currently, the hibmcge netdev acquires the rtnl_lock in
> pci_error_handlers.reset_prepare() and releases it in
> pci_error_handlers.reset_done().
> 
> However, in the PCI framework:
> pci_reset_bus - __pci_reset_slot - pci_slot_save_and_disable_locked -
>  pci_dev_save_and_disable - err_handler->reset_prepare(dev);
> 
> In pci_slot_save_and_disable_locked():
> 	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
> 		if (!dev->slot || dev->slot!= slot)
> 			continue;
> 		pci_dev_save_and_disable(dev);
> 		if (dev->subordinate)
> 			pci_bus_save_and_disable_locked(dev->subordinate);
> 	}
> 
> This will iterate through all devices under the current bus and execute
> err_handler->reset_prepare(), causing two devices of the hibmcge driver
> to sequentially request the rtnl_lock, leading to a deadlock.
> 
> Since the driver now executes netif_device_detach()
> before the reset process, it will not concurrently with
> other netdev APIs, so there is no need to hold the rtnl_lock now.
> 
> Therefore, this patch removes the rtnl_lock during the reset process and
> adjusts the position of HBG_NIC_STATE_RESETTING to ensure
> that multiple resets are not executed concurrently.
> 
> Fixes: 3f5a61f6d504f ("net: hibmcge: Add reset supported in this module")
> Signed-off-by: Jijie Shao <shaojijie@...wei.com>
> ---
> ChangeLog:
> v1 -> v2:
>   - Fix a concurrency issue, suggested by Simon Horman
>   v1: https://lore.kernel.org/all/20250731134749.4090041-1-shaojijie@huawei.com/

Thanks for the update.

This version looks good to me.

Reviewed-by: Simon Horman <horms@...nel.org>