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Date: Fri, 4 Sep 2026 14:20:33 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Yury Murashka <yurypm@arista.com>
Cc: bhelgaas@google.com, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org, James Sewart <jamessewart@arista.com>
Subject: Re: [PATCH] PCI: Stop waiting for link status after config read
 failure
Message-ID: <apq3kd9_qsURNpKu@wunner.de>
References: <20260904111318.1063858-1-yurypm@arista.com>
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In-Reply-To: <20260904111318.1063858-1-yurypm@arista.com>

On Fri, Sep 04, 2026 at 11:13:18AM +0000, Yury Murashka wrote:
> With a nested PCIe topology with multiple layers of hotplug, a link can go
> down near the bottom of the topology shortly before a link above it goes
> down. In that case, pcie_wait_for_link_status() can wait for the full
> timeout while every read of the link status register fails because the
> device has disappeared.
> 
> Return immediately when reading the link status fails so event processing
> can continue.
[...]
> +++ b/drivers/pci/pci.c
> @@ -4580,7 +4581,8 @@ static int pcie_wait_for_link_status(struct pci_dev *pdev,
>  
>  	end_jiffies = jiffies + msecs_to_jiffies(PCIE_LINK_RETRAIN_TIMEOUT_MS);
>  	do {
> -		pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta);
> +		if (pcie_capability_read_word(pdev, PCI_EXP_LNKSTA, &lnksta))
> +			return -ENODEV;
>  		if ((lnksta & lnksta_mask) == lnksta_match)
>  			return 0;
>  		msleep(1);

It might be clearer if you check for pci_dev_is_disconnected() directly
instead of relying on a PCIBIOS_DEVICE_NOT_FOUND return value which is
generated as a side effect of the device being gone.

Thanks,

Lukas