linux-kernel - Re: [PATCH v11 3/7] PCI/ERR: add mutex to synchronize recovery

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Message-ID: <20180223234525.GQ14632@bhelgaas-glaptop.roam.corp.google.com>
Date:   Fri, 23 Feb 2018 17:45:25 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Oza Pawandeep <poza@...eaurora.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dongdong Liu <liudongdong3@...wei.com>,
        Keith Busch <keith.busch@...el.com>, Wei Zhang <wzhang@...com>,
        Sinan Kaya <okaya@...eaurora.org>,
        Timur Tabi <timur@...eaurora.org>
Subject: Re: [PATCH v11 3/7] PCI/ERR: add mutex to synchronize recovery

On Fri, Feb 23, 2018 at 01:54:00PM +0530, Oza Pawandeep wrote:
> This patch protects pci_do_recovery with mutex.

pcie_do_recovery()

Please explain why the mutex is necessary.  What bad things happen
without the mutex?

You named (some) of the other things "pcie"; maybe use "pcie" in the
mutex name as well so they look the same.

> Signed-off-by: Oza Pawandeep <poza@...eaurora.org>
> 
> diff --git a/drivers/pci/pcie/pcie-err.c b/drivers/pci/pcie/pcie-err.c
> index fcd5add..f830975 100644
> --- a/drivers/pci/pcie/pcie-err.c
> +++ b/drivers/pci/pcie/pcie-err.c
> @@ -20,6 +20,8 @@
>  #include <linux/pcieport_if.h>
>  #include "portdrv.h"
>  
> +static DEFINE_MUTEX(pci_err_recovery_lock);
> +
>  struct aer_broadcast_data {
>  	enum pci_channel_state state;
>  	enum pci_ers_result result;
> @@ -283,6 +285,8 @@ void pcie_do_recovery(struct pci_dev *dev, int severity)
>  	pci_ers_result_t status, result = PCI_ERS_RESULT_RECOVERED;
>  	enum pci_channel_state state;
>  
> +	mutex_lock(&pci_err_recovery_lock);
> +
>  	if (severity == AER_FATAL)
>  		state = pci_channel_io_frozen;
>  	else
> @@ -326,9 +330,11 @@ void pcie_do_recovery(struct pci_dev *dev, int severity)
>  				report_resume);
>  
>  	dev_info(&dev->dev, "Device recovery successful\n");
> +	mutex_unlock(&pci_err_recovery_lock);
>  	return;
>  
>  failed:
>  	/* TODO: Should kernel panic here? */
>  	dev_info(&dev->dev, "Device recovery failed\n");
> +	mutex_unlock(&pci_err_recovery_lock);
>  }
> -- 
> Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.,
> a Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
>